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Journal articles on the topic 'Macrophage activation'
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Sharma, Preeti, Shailza Shreshtha, Pradeep Kumar, Rachna Sharma, and T. K. Mahapatra. "A Review on Macrophage Activation Syndrome." Journal of Pure and Applied Microbiology 13, no. 1 (March 31, 2019): 183–91. http://dx.doi.org/10.22207/jpam.13.1.19.
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Gilbreath, M. J., C. A. Nacy, D. L. Hoover, C. R. Alving, G. M. Swartz, and M. S. Meltzer. "Macrophage activation for microbicidal activity against Leishmania major: inhibition of lymphokine activation by phosphatidylcholine-phosphatidylserine liposomes." Journal of Immunology 134, no. 5 (May 1, 1985): 3420–25. http://dx.doi.org/10.4049/jimmunol.134.5.3420.
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Abstract Resident peritoneal macrophages from untreated mice develop microbicidal activity against amastigotes of the protozoan parasite Leishmania tropica (current nomenclature = Leishmania major) after in vitro exposure to LK from antigen-stimulated leukocyte culture fluids. This LK-induced macrophage microbicidal activity was completely abrogated by addition of 7:3 phosphatidylcholine: phosphatidylserine liposomes. Liposome inhibition was not due to direct toxic effects against the parasite or macrophage effector cell; factors in LK that induce macrophage microbicidal activity were not adsorbed or destroyed by liposome treatment. Other phagocytic particles, such as latex beads, had no effect on microbicidal activity. Moreover, liposome inhibition of activated macrophage effector function was relatively selective: LK-induced macrophage tumoricidal activity was not affected by liposome treatment. Liposome inhibition was dependent upon liposome dose (5 nmoles/culture) and time of addition of leishmania-infected, LK-treated macrophage cultures. Addition of liposomes through the initial 8 hr of culture completely inhibited LK-induced macrophage microbicidal activity; liposomes added after 16 hr had no effect. Similarly, microbicidal activity by macrophages activated in vivo by BCG or Corynebacterium parvum was not affected by liposome treatment. Liposome treatment also did not affect the increased resistance to infection induced in macrophages by LK. These data suggest that liposomes interfere with one or more early events in the induction of activated macrophages (macrophage-LK interaction) and not with the cytotoxic mechanism itself (parasite-macrophage interaction). These studies add to the growing body of data that implicate cell lipid in regulatory events controlling macrophage effector function.
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Van Epps, Heather L. "Macrophage activation unveiled." Journal of Experimental Medicine 202, no. 7 (October 3, 2005): 884. http://dx.doi.org/10.1084/jem.2027fta.
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In the early 1960s, George Mackaness showed that macrophages from mice infected with intracellular bacteria could launch an indiscriminate attack against unrelated bacteria. Thus began an explosion of research on the biology of what Mackaness first termed “macrophage activation.”
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Heidenreich, S., M. Weyers, J. H. Gong, H. Sprenger, M. Nain, and D. Gemsa. "Potentiation of lymphokine-induced macrophage activation by tumor necrosis factor-alpha." Journal of Immunology 140, no. 5 (March 1, 1988): 1511–18. http://dx.doi.org/10.4049/jimmunol.140.5.1511.
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Abstract In this study, we examined the possible role of TNF-alpha and lymphotoxin (TNF-beta) as cofactors of macrophage activation. The results demonstrate that both TNF were capable of enhancing the cytostatic and cytolytic activity of murine peritoneal macrophages against Eb lymphoma cells. The potentiation of tumor cytotoxicity became apparent when macrophages from DBA/2 mice were suboptimally activated by either a T cell clone-derived macrophage-activating factor or by IFN-gamma plus LPS. Neither TNF-alpha nor TNF-beta could induce tumor cytotoxicity in IFN-gamma-primed macrophages, indicating that TNF cannot replace LPS as a triggering signal of activation. In LPS-resistant C3H/HeJ macrophages, which were unresponsive to IFN-gamma plus LPS, a supplementation with TNF fully restored activation to tumor cytotoxicity. Furthermore, TNF-alpha potentiated a variety of other functions in low-level activated macrophages such as a lactate production and release of cytotoxic factors. At the same time, TNF-alpha produced a further down-regulation of pinocytosis, tumor cell binding and RNA synthesis observed in activated macrophages. These data demonstrate new activities for both TNF-alpha and TNF-beta as helper factors that facilitate macrophage activation. In particular, the macrophage product TNF-alpha may serve as an autocrine signal to potentiate those macrophage functions that were insufficiently activated by lymphokines.
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Zhao, Yu, Yuteng Jiang, Fengmei Wang, Li Sun, Mengyuan Ding, Liyuan Zhang, Beibei Wu, and Xiaoliang Zhang. "High glucose promotes macrophage switching to the M1 phenotype via the downregulation of STAT-3 mediated autophagy." PLOS ONE 19, no. 12 (December 31, 2024): e0314974. https://doi.org/10.1371/journal.pone.0314974.
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Aim Imbalanced M1/M2 macrophage phenotype activation is a key point in diabetic kidney disease (DKD). Macrophages mainly exhibit the M1 phenotype, which contributes to inflammation and fibrosis in DKD. Studies have indicated that autophagy plays an important role in M1/M2 activation. However, the mechanism by which autophagy regulates the macrophage M1/M2 phenotype in DKD is unknown. Thus, the aim of the present study was to explore whether high glucose-induced macrophages switch to the M1 phenotype via the downregulation of STAT-3-mediated autophagy. Methods DKD model rats were established in vivo via the intraperitoneal injection of streptozocin (STZ). The rats were sacrificed at 18 weeks for histological and molecular analysis. RAW264.7 cells were cultured in vitro with 30 mM glucose in the presence or absence of a STAT-3 activator (colivelin) and an autophagy activator (rapamycin). Moreover, M1 and M2 macrophage activation models were established as a control group. Immunofluorescence and Western blot analyses were used to detect the expression of autophagy-related proteins (LC3 and Beclin-1), M1 markers (iNOS and CD11c) and M2 markers (MR and CD206). Results In DKD, macrophages exhibit an M1 phenotype. Under high-glucose conditions, RAW264.7 macrophages switched to the M1 phenotype. Autophagy was downregulated in high glucose–induced M1 macrophages. Both the STAT-3 activator and the autophagy activator promoted the transition of glucose-induced M1 macrophages to M2 macrophages. Moreover, STAT-3 activation increased the expression of autophagy markers (LC3 and Beclin-1). However, the autophagy activator had no effect on STAT-3 phosphorylation. Conclusion High glucose promotes macrophage switching to the M1 phenotype via the downregulation of STAT-3-mediated autophagy.
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McGee, MP, R. Wallin, FB Wheeler, and H. Rothberger. "Initiation of the extrinsic pathway of coagulation by human and rabbit alveolar macrophages: a kinetic study." Blood 74, no. 5 (October 1, 1989): 1583–90. http://dx.doi.org/10.1182/blood.v74.5.1583.1583.
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Abstract We examined assembly and expression of the factor X activating complex on human and rabbit alveolar macrophages. Kinetic parameters of the factor X activating reaction were determined by functional titrations of factors VII and X with macrophage tissue factor (TF) added. We found rapid activation of factor X to Xa on alveolar macrophage surfaces. Detection of rapid factor Xa formation on macrophages required addition of exogenous factors VII and X. At plasma concentrations of the purified factors, factor Xa was formed on freshly isolated macrophages at approximately 5.4 pmol/min/10(6) cells. After macrophage maturation in culture for 20 hours with LPS (endotoxin) added, the factor X activation rate was increased two- to sixfold. The km' (apparent km) of TF-factor VII enzymatic complexes assembled on alveolar macrophages for factor X were (258 +/- 55 and 475 +/- 264 nmol/L for human and rabbit cells, respectively). The km' did not change during macrophage maturation in culture, but V'max (apparent Vmax) was consistently increased. The K1/2 of human factor VII (concentrations giving half maximal rates of factor X activation) for the interaction with human and rabbit alveolar macrophage TF were 0.191 +/- 0.096 and 1.7 +/- 0.7 etamol/L, respectively. The K1/2 were not significantly changed after maturation, whereas rates of Xa formation at saturation with factor VII were increased. The fast rates of factor X activation observed at physiologic concentrations of plasma-derived factors VII and X indicate that TF on alveolar macrophages is likely to provide sites for binding of factor VII and activation of factor X in vivo during clotting reactions associated with alveolar edema and inflammation.
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McGee, MP, R. Wallin, FB Wheeler, and H. Rothberger. "Initiation of the extrinsic pathway of coagulation by human and rabbit alveolar macrophages: a kinetic study." Blood 74, no. 5 (October 1, 1989): 1583–90. http://dx.doi.org/10.1182/blood.v74.5.1583.bloodjournal7451583.
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We examined assembly and expression of the factor X activating complex on human and rabbit alveolar macrophages. Kinetic parameters of the factor X activating reaction were determined by functional titrations of factors VII and X with macrophage tissue factor (TF) added. We found rapid activation of factor X to Xa on alveolar macrophage surfaces. Detection of rapid factor Xa formation on macrophages required addition of exogenous factors VII and X. At plasma concentrations of the purified factors, factor Xa was formed on freshly isolated macrophages at approximately 5.4 pmol/min/10(6) cells. After macrophage maturation in culture for 20 hours with LPS (endotoxin) added, the factor X activation rate was increased two- to sixfold. The km' (apparent km) of TF-factor VII enzymatic complexes assembled on alveolar macrophages for factor X were (258 +/- 55 and 475 +/- 264 nmol/L for human and rabbit cells, respectively). The km' did not change during macrophage maturation in culture, but V'max (apparent Vmax) was consistently increased. The K1/2 of human factor VII (concentrations giving half maximal rates of factor X activation) for the interaction with human and rabbit alveolar macrophage TF were 0.191 +/- 0.096 and 1.7 +/- 0.7 etamol/L, respectively. The K1/2 were not significantly changed after maturation, whereas rates of Xa formation at saturation with factor VII were increased. The fast rates of factor X activation observed at physiologic concentrations of plasma-derived factors VII and X indicate that TF on alveolar macrophages is likely to provide sites for binding of factor VII and activation of factor X in vivo during clotting reactions associated with alveolar edema and inflammation.
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Lewis, Brandon W., Sonika Patial, and Yogesh Saini. "In Vitro Screening Method for Characterization of Macrophage Activation Responses." Methods and Protocols 5, no. 5 (August 30, 2022): 68. http://dx.doi.org/10.3390/mps5050068.
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Macrophage activation refers to the enhanced functionality of macrophages in response to endogenous or exogenous stimuli. Due to the existence of limitless stimuli and a multitude of receptors on macrophage surfaces, the nature of activation (or acquired functioning) can be specific to the encountering stimulus. This article describes a macrophage-activation screening platform in a 96-well format. The methodology involves the generation of bone marrow-derived macrophages, their activation into two extreme activation states, and screening of activated macrophages for expression of bonafide protein biomarkers. A high-throughput and stringent assay to determine macrophage activation markers developed in this article can be adapted for biomarker determination in pathological conditions and toxicant/drug safety screening.
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Rios, Francisco J., Marianna M. Koga, Mateus Pecenin, Matheus Ferracini, Magnus Gidlund, and S. Jancar. "Oxidized LDL Induces Alternative Macrophage Phenotype through Activation of CD36 and PAFR." Mediators of Inflammation 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/198193.
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OxLDL is recognized by macrophage scavenger receptors, including CD36; we have recently found that Platelet-Activating Factor Receptor (PAFR) is also involved. Since PAFR in macrophages is associated with suppressor function, we examined the effect of oxLDL on macrophage phenotype. It was found that the presence of oxLDL during macrophage differentiation induced high mRNA levels to IL-10, mannose receptor, PPARγand arginase-1 and low levels of IL-12 and iNOS. When human THP-1 macrophages were pre-treated with oxLDL then stimulated with LPS, the production of IL-10 and TGF-βsignificantly increased, whereas that of IL-6 and IL-8 decreased. In murine TG-elicited macrophages, this protocol significantly reduced NO, iNOS and COX2 expression. Thus, oxLDL induced macrophage differentiation and activation towards the alternatively activated M2-phenotype. In murine macrophages, oxLDL induced TGF-β, arginase-1 and IL-10 mRNA expression, which were significantly reduced by pre-treatment with PAFR antagonists (WEB and CV) or with antibodies to CD36. The mRNA expression of IL-12, RANTES and CXCL2 were not affected. We showed that this profile of macrophage activation is dependent on the engagement of both CD36 and PAFR. We conclude that oxLDL induces alternative macrophage activation by mechanisms involving CD36 and PAFR.
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Valledor, Annabel F., Luís Arpa, Ester Sánchez-Tilló, Mònica Comalada, Cristina Casals, Jordi Xaus, Carme Caelles, Jorge Lloberas та Antonio Celada. "IFN-γ–mediated inhibition of MAPK phosphatase expression results in prolonged MAPK activity in response to M-CSF and inhibition of proliferation". Blood 112, № 8 (15 жовтня 2008): 3274–82. http://dx.doi.org/10.1182/blood-2007-11-123604.
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Abstract Macrophages have the capacity to proliferate in response to specific growth factors, such as macrophage-colony stimulating factor (M-CSF). In the presence of several cytokines and activating factors, macrophages undergo growth arrest, become activated, and participate in the development of an immune response. We have previously observed that activation of extracellularly regulated kinase 1/2 (ERK-1/2) is required for macrophage proliferation in response to growth factors. A short and early pattern of ERK activity correlated with the proliferative response. In contrast, slightly prolonged patterns of activity of these kinases were induced by signals that lead to macrophage activation and growth arrest. IFN-γ is the main endogenous Th1-type macrophage activator. Here we report that stimulation with IFN-γ prolongs the pattern of ERK activity induced by M-CSF in macrophages. These effects correlate with IFN-γ–mediated inhibition of the expression of several members of the MAPK phosphatase family, namely MKP-1, -2, and -4. Moreover, inhibition of MKP-1 expression using siRNA technology or synthetic inhibitors also led to elongated ERK activity and significant blockage of M-CSF–dependent proliferation. These data suggest that subtle changes in the time course of activity of members of the MAPK family contribute to the antiproliferative effects of IFN-γ in macrophages.
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Davis, Spring, Aiko M. Cirone, Janet Menzie, Floyd Russell, C. Kathleen Dorey, Yoshimi Shibata, Jianning Wei, and Changlong Nan. "Phagocytosis-mediated M1 activation by chitin but not by chitosan." American Journal of Physiology-Cell Physiology 315, no. 1 (July 1, 2018): C62—C72. http://dx.doi.org/10.1152/ajpcell.00268.2017.
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Chitin particles have been used to understand host response to chitin-containing pathogens and allergens and are known to induce a wide range of polarized macrophage activations, depending, at least in part, on particle size. Nonphagocytosable particles larger than a macrophage induce tissue repair M2 activation. In contrast, phagocytosable chitin microparticles (CMPs, 1–10 μm diameters) induce M1 macrophages that kill intracellular microbes and damage tissues. However, chitosan (deacetylated) microparticles (de-CMPs, 1–10 µm) induce poor M1 activation. Toll-like receptor 2 (TLR2) and associated coreceptors in macrophages appear to be required for the M1 activation. To understand the exact mechanism of phagocytosis-mediated M1 activation by chitin, we isolated macrophage proteins that bind to CMPs during early phagocytosis and determined that TLR1, TLR2, CD14, late endosomal/lysosomal adaptor MAPK and mechanistic target of rapamycin activator 1 (LAMTOR1), Lck/Yes novel tyrosine kinase (Lyn), and β-actin formed phagosomal CMP-TLR2 clusters. These proteins were also detected in TLR2 phagosomal clusters in macrophages phagocytosing de-CMPs, but at relatively lower levels than in the CMP-TLR2 clusters. Importantly, CMP-TLR2 clusters further recruited myeloid differentiation primary response gene 88 (MyD88) and Toll-IL-1 receptor-containing adaptor protein (TIRAP) and phosphorylated Lyn, whereas neither the adaptors nor phosphorylated Lyn was detected in the de-CMP clusters. The results indicate that the acetyl group played an obligatory, phagocytosis-dependent role in the initiation of an integrated signal for TLR2-mediated M1 activation.
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ONOZAKI, Kikuo. "Macrophage activation by macrophage activation factor, macrophage migration inhibitory factor." Nippon Saikingaku Zasshi 40, no. 5 (1985): 811–17. http://dx.doi.org/10.3412/jsb.40.811.
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Leopold Wager, Chrissy M., Camaron R. Hole, Karen L. Wozniak, Michal A. Olszewski, Mathias Mueller, and Floyd L. Wormley. "STAT1 Signaling within Macrophages Is Required for Antifungal Activity against Cryptococcus neoformans." Infection and Immunity 83, no. 12 (September 8, 2015): 4513–27. http://dx.doi.org/10.1128/iai.00935-15.
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Cryptococcus neoformans, the predominant etiological agent of cryptococcosis, is an opportunistic fungal pathogen that primarily affects AIDS patients and patients undergoing immunosuppressive therapy. In immunocompromised individuals,C. neoformanscan lead to life-threatening meningoencephalitis. Studies using a virulent strain ofC. neoformansengineered to produce gamma interferon (IFN-γ), denoted H99γ, demonstrated that protection against pulmonaryC. neoformansinfection is associated with the generation of a T helper 1 (Th1)-type immune response and signal transducer and activator of transcription 1 (STAT1)-mediated classical (M1) macrophage activation. However, the critical mechanism by which M1 macrophages mediate their anti-C. neoformansactivity remains unknown. The current studies demonstrate that infection withC. neoformansstrain H99γ in mice with macrophage-specific STAT1 ablation resulted in severely increased inflammation of the pulmonary tissue, a dysregulated Th1/Th2-type immune response, increased fungal burden, deficient M1 macrophage activation, and loss of protection. STAT1-deficient macrophages produced significantly less nitric oxide (NO) than STAT1-sufficient macrophages, correlating with an inability to control intracellular cryptococcal proliferation, even in the presence of reactive oxygen species (ROS). Furthermore, macrophages from inducible nitric oxide synthase knockout mice, which had intact ROS production, were deficient in anticryptococcal activity. These data indicate that STAT1 activation within macrophages is required for M1 macrophage activation and anti-C. neoformansactivity via the production of NO.
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Timmer, Anjuli M., та Victor Nizet. "IKKβ/NF-κB and the miscreant macrophage". Journal of Experimental Medicine 205, № 6 (2 червня 2008): 1255–59. http://dx.doi.org/10.1084/jem.20081056.
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Macrophage activation relies on complex intracellular signaling processes that integrate the need for rapid inflammatory responses to pathogens with the need to resolve inflammation without permanent harm to normal tissues. Patterns of aberrant macrophage activation characterize and sustain disorders of chronic inflammation, infection, and cancer. New studies now show a role for the NF-κB activator IKKβ in promoting an alternative, immunosuppressive pattern of macrophage activation, which limits the cell's tumoricidal and bactericidal capacities. As cancers and pathogens may have evolved multiple mechanisms to manipulate macrophages for their own survival, is there anything we can do about it?
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Huang, Wei, Itsuko Ishii, Wei-Yang Zhang, Miyahiko Sonobe, and Howard S. Kruth. "PMA activation of macrophages alters macrophage metabolism of aggregated LDL." Journal of Lipid Research 43, no. 8 (August 2002): 1275–82. http://dx.doi.org/10.1194/jlr.m100436-jlr200.
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Aggregation of LDL may contribute to its retention in atherosclerotic lesions. Previously, we showed that aggregated LDL induces and enters surface-connected compartments (SCCs) in human monocyte-derived macrophages by a process we have named patocytosis. Aggregated LDL was disaggregated and released from SCCs of macrophages when exposed to human lipoprotein-deficient serum. The serum factor that mediated aggregated LDL release and disaggregation was plasmin generated from plasminogen by macrophage urokinase plasminogen activator. We now show that activation of macrophages with PMA inhibits plasmin-mediated release of aggregated LDL from macrophages. With macrophage activation, plasminogen released about 60% less cholesterol and 63% less TCA-insoluble 125I-aggregated LDL than when macrophages were not activated. Electron microscopy showed that PMA did not cause SCCs to close, which could have trapped aggregated LDL within the SCCs and limited protease access to aggregated LDL. Rather, PMA decreased macrophage generation of plasmin by 61%, and stimulated lysosomal degradation of aggregated LDL by more than 2-fold. Degradation was mediated by protein kinase C, shown by the finding that degradation was inhibited by the protein kinase C inhibitor Gö6976. PMA-stimulated degradation of aggregated LDL was associated with a 3-fold increase in cholesterol esterification, consistent with hydrolysis and re-esterification of aggregated LDL-derived cholesteryl ester.In conclusion, macrophage activation with PMA causes more of the aggregated LDL that enters macrophage SCCs to be metabolized by lysosomes. This results in more cholesterol to be stored in macrophages and less aggregated LDL to be available for plasmin-mediated release from macrophage SCCs.
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Wyler, D. J., D. I. Beller, and J. P. Sypek. "Macrophage activation for antileishmanial defense by an apparently novel mechanism." Journal of Immunology 138, no. 4 (February 15, 1987): 1246–49. http://dx.doi.org/10.4049/jimmunol.138.4.1246.
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Abstract Activation of macrophages by lymphokines (including interferon-gamma; IFN-gamma) is presently considered to be a major host defense mechanism against a number of intracellular microorganisms. In a series of earlier studies that made use of mice undergoing spontaneous resolution of footpad infections with Leishmania major, we obtained evidence suggesting that a subpopulation of Leishmania-sensitized lymph node T lymphocytes could activate antimicrobial effects in Leishmania-infected macrophages by an apparently lymphokine-independent mechanism. These effector lymphocytes are not cytotoxic to host cells, and their effects are antigen specific and genetically restricted. To more rigorously investigate this apparently novel mechanism of macrophage activation, we examined the effect of blocking lymphokine production with cyclosporin A (CSA) on the capacity of these effector lymphocytes to exert macrophage activating function. Although CSA blocked lymphokines that activate antileishmanial effects, it did not inhibit the antimicrobial capacity of the effector lymphocytes. We also confirmed that IFN-gamma is the major macrophage-activating lymphokine that induces antileishmanial effects; treatment of lymphokine-containing supernatants with anti-IFN-gamma antibody markedly reduced their antimicrobial effects. In contrast, treatment of effector lymphocytes with this antibody failed to reduce their macrophage-activating capacity. We conclude that there exists an apparently novel macrophage-activating mechanism for antimicrobial defense that is independent of soluble lymphokine mediators.
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Stout, R. D., J. Suttles, J. Xu, I. S. Grewal, and R. A. Flavell. "Impaired T cell-mediated macrophage activation in CD40 ligand-deficient mice." Journal of Immunology 156, no. 1 (January 1, 1996): 8–11. http://dx.doi.org/10.4049/jimmunol.156.1.8.
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Abstract The expression of the ligand for CD40 (CD40L) is critical for induction of T cell-dependent Ab responses. To examine how critical the expression of CD40L is for induction of cell-mediated immune responses, the ability of T cells from CD40L knockout mice to activate macrophage effector function was assessed. CD4+ T cells from CD40L-knockout mice were fourfold less effective than +/+ T cells in activating the nitric oxide response in allogeneic macrophages. CD40L-knockout T cells that were fixed with paraformaldehyde after a 6-h activation period, a time point at which CD40L dominates the macrophage-activating capability of the T cell, could activate neither macrophage production of inflammatory cytokines (TNF-alpha) nor generation of reactive nitrogen intermediates. After 24 h of activation, however, both CD40L-knockout and +/+ T cells could induce similar but weak responses from the macrophages. This study demonstrates that animals deficient in CD40L expression display a deficiency in T cell-dependent macrophage-mediated immune responses.
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Yu, Tingting, Yong Zuo, Rong Cai, Xian Huang, Shuai Wu, Chenxi Zhang, Y. Eugene Chin та ін. "SENP1 regulates IFN-γ−STAT1 signaling through STAT3−SOCS3 negative feedback loop". Journal of Molecular Cell Biology 9, № 2 (26 жовтня 2016): 144–53. http://dx.doi.org/10.1093/jmcb/mjw042.
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Abstract Interferon-γ (IFN-γ) triggers macrophage for inflammation response by activating the intracellular JAK−STAT1 signaling. Suppressor of cytokine signaling 1 (SOCS1) and protein tyrosine phosphatases can negatively modulate IFN-γ signaling. Here, we identify a novel negative feedback loop mediated by STAT3−SOCS3, which is tightly controlled by SENP1 via de-SUMOylation of protein tyrosine phosphatase 1B (PTP1B), in IFN-γ signaling. SENP1-deficient macrophages show defects in IFN-γ signaling and M1 macrophage activation. PTP1B in SENP1-deficient macrophages is highly SUMOylated, which reduces PTP1B-induced de-phosphorylation of STAT3. Activated STAT3 then suppresses STAT1 activation via SOCS3 induction in SENP1-deficient macrophages. Accordingly, SENP1-deficient macrophages show reduced ability to resist Listeria monocytogenes infection. These results reveal a crucial role of SENP1-controlled STAT1 and STAT3 balance in macrophage polarization.
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Zhang, Ronghua, Tienan Wang, and Qing Lin. "847 Inflammasome activation in M2 macrophage restrain the immune suppressive function." Journal for ImmunoTherapy of Cancer 8, Suppl 3 (November 2020): A900. http://dx.doi.org/10.1136/jitc-2020-sitc2020.0847.
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BackgroundMacrophage is an important component in tumor microenvironment (TME) and plays multiple roles in tumor initiation, progression and metastases. In response to various stimuli within TME, macrophage exhibits high level of functional heterogeneity. There are two distinct groups of macrophages: M1 macrophage exhibits pro-inflammatory phenotype with high levels of TNF-a, IL-6, and IL-1ß, while M2 macrophage displays immune suppressive phenotype with high levels of anti-inflammatory cytokines such as IL-10 and TGF-ß. In response to the M2 cytokines, myeloid cells within the TME further acquire higher expression of PD-L1 and thus inactivate T cells. M2 cytokines can also directly inhibit T cell activation. As a result, re-polarizing M2 macrophages becomes a key concept for cancer immunotherapy. The NLRP3 inflammasome is acquired by macrophages to fight against endogenous danger signals. Macrophage NLRP3 activation has been observed in several tumor models, but the function of NLRP3 on macrophage polarity remains controversial. Inflammasome activation with IL-1ß/IL-18 secretion was reported to promote M1 polarization. However, NLRP3 activation was also reported to promote M2 polarity through up-regulation of IL4 in asthma modelMethodsHere, we have established an in vitro human macrophage NLRP3 activation system (figure 1), coupled with M2 macrophage polarization assay, to dissect the role of NLRP3 in macrophage phenotype.ResultsOur results indicate that NLRP3 activation restrained M2 phenotype and further enhanced T cell activation in an M2/T cell co-culture system (figure 2).Abstract 847 Figure 1Inflammasome activation polarize M2 macrophage intUse LPS/ATP to stimulate NLRP3 in M2 macrophage and demonstrate NLRP3 activation could reduce CD163 and increase CD86Abstract 847 Figure 2Inflammasome in M2 rescue T cell activationestablish M2/T co-culture system in vitro to demonstrate M2 could suppress T activation while Inflammatory M2 could partial rescue the suppressive phenotypeConclusionsInflammasome could be the potential target for cancer by modulating T cell activation through macrophage polarization regulation
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Serraj Andaloussi, Meriem, Hayat Midyani, Chadia Khalloufi, Amine Lamrissi, Karima Fichtali, Said Bouhya, Salah Hayar, Ihsane Moussaid, Smaïl El Youssoufi, and Said Salmi. "Macrophage Activation Syndrome Discovered During Pregnancy: Case Report." Obstetrics Gynecology and Reproductive Sciences 5, no. 7 (September 25, 2021): 01–04. http://dx.doi.org/10.31579/2578-8965/081.
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Macrophage activation syndrome (MAS) or Haemophagocytic syndrome (HPS) results from an inappropriate stimulation of macrophages in bone marrow and lymphoid organs, leading to haemophagocytosis and hypercytokinemia. HPS may be primitive, essentially in pediatric population, or secondary to malignancy, infection or autoimmune disease. This disease is rare and prognosis is poor. The diagnosis of hemophagocytic syndrome remains a challenge especially during pregnancy. We report a case collected at the Elharouchimaternity service, taken in charge jointly with its intensive care unit, of a 26-year-old patient with no pathological history leading to an unsuccessful pregnancy presumed at 5 months in whom the MAS syndrome was retained due to pancytopenia. , hyperferitinemia, hypertriglyceridemia with the presence of a few hemophagocytes in the myelogram with a good evolution under bolus of solumedrol and symptomatic treatment. We discuss through this case the diagnostic difficulties, the obstetric complications as well as the options therapeutic.
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Oppong-Nonterah, Gertrude O., Omar Lakhdari, Asami Yamamura, Hal M. Hoffman, and Lawrence S. Prince. "TLR Activation Alters Bone Marrow-Derived Macrophage Differentiation." Journal of Innate Immunity 11, no. 1 (November 8, 2018): 99–108. http://dx.doi.org/10.1159/000494070.
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Early exposure to inflammatory signals may have a lasting impact on immune function. Present throughout embryogenesis, macrophages are key cells providing innate immune protection to the developing fetus and newborn. Here, we have used an established model of macrophage development to test how early inflammatory signals can impact cellular differentiation and function. Bone marrow-derived macrophages were treated with Escherichia coli lipopolysaccharide (LPS) 2 days after initial isolation and culture. LPS treatment during this early stage of differentiation decreased the expression of CSF1R and increased that of the mature macrophage marker F4/80. These early changes in macrophage differentiation were also measured in cells from mice lacking IKKβ, but the change in CSF1R expression after LPS treatment was blocked with MAPK inhibition. LPS-induced changes in macrophage marker expression persisted following LPS removal, suggesting that early inflammatory activation could induce a lasting developmental impact. Early LPS exposure inhibited macrophage phagocytosis of labeled E. coli while LPS had no effect on fully differentiated macrophages. Our data demonstrate that early inflammatory exposure to a microbial stimulus induce lasting phenotypic changes in macrophages.
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Hardbower, Dana M., Mohammad Asim, Paula B. Luis, Kshipra Singh, Daniel P. Barry, Chunying Yang, Meredith A. Steeves, et al. "Ornithine decarboxylase regulates M1 macrophage activation and mucosal inflammation via histone modifications." Proceedings of the National Academy of Sciences 114, no. 5 (January 17, 2017): E751—E760. http://dx.doi.org/10.1073/pnas.1614958114.
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Macrophage activation is a critical step in host responses during bacterial infections. Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine metabolism, has been well studied in epithelial cells and is known to have essential roles in many different cellular functions. However, its role in regulating macrophage function during bacterial infections is not well characterized. We demonstrate that macrophage-derived ODC is a critical regulator of M1 macrophage activation during bothHelicobacter pyloriandCitrobacter rodentiuminfection. Myeloid-specificOdcdeletion significantly increased gastric and colonic inflammation, respectively, and enhanced M1 activation. Add-back of putrescine, the product of ODC, reversed the increased macrophage activation, indicating that ODC and putrescine are regulators of macrophage function.Odc-deficient macrophages had increased histone 3, lysine 4 (H3K4) monomethylation, and H3K9 acetylation, accompanied by decreased H3K9 di/trimethylation both in vivo and ex vivo in primary macrophages. These alterations in chromatin structure directly resulted in up-regulated gene transcription, especially M1 gene expression. Thus, ODC in macrophages tempers antimicrobial, M1 macrophage responses during bacterial infections through histone modifications and altered euchromatin formation, leading to the persistence and pathogenesis of these organisms.
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Seljelid, R. "Macrophage Activation." Scandinavian Journal of Rheumatology 17, sup76 (January 1988): 67–72. http://dx.doi.org/10.3109/03009748809102954.
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Petit, J. F., and G. Lemaire. "Macrophage activation." Annales de l'Institut Pasteur / Immunologie 137 (January 1986): 191–92. http://dx.doi.org/10.1016/s0771-050x(86)80024-9.
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Pinder, M. "Macrophage activation." Veterinary Immunology and Immunopathology 14, no. 2 (February 1987): 205–6. http://dx.doi.org/10.1016/0165-2427(87)90055-9.
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Pedicillo, Maria Carmela, Ilenia Sara De Stefano, Rosanna Zamparese, Raffaele Barile, Mario Meccariello, Alessio Agostinone, Giuliana Villani, et al. "The Role of Toll-like Receptor-4 in Macrophage Imbalance in Lethal COVID-19 Lung Disease, and Its Correlation with Galectin-3." International Journal of Molecular Sciences 24, no. 17 (August 26, 2023): 13259. http://dx.doi.org/10.3390/ijms241713259.
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To the current data, there have been 6,955,141 COVID-19-related deaths worldwide, reported to WHO. Toll-like receptors (TLRs) implicated in bacterial and virus sensing could be a crosstalk between activation of persistent innate-immune inflammation, and macrophage’s sub-population alterations, implicated in cytokine storm, macrophage over-activation syndrome, unresolved Acute Respiratory Disease Syndrome (ARDS), and death. The aim of this study is to demonstrate the association between Toll-like-receptor-4 (TLR-4)-induced inflammation and macrophage imbalance in the lung inflammatory infiltrate of lethal COVID-19 disease. Twenty-five cases of autopsy lung tissues were studied by digital pathology-based immunohistochemistry to evaluate expression levels of TLR-4 (CD 284), pan-macrophage marker CD68 (clone KP1), sub-population marker related to alveolar macrophage Galectin-3 (GAL-3) (clone 9C4), and myeloid derived CD163 (clone MRQ-26), respectively. SARS-CoV-2 viral persistence has been evaluated by in situ hybridation (ISH) method. This study showed TLR-4 up-regulation in a subgroup of patients, increased macrophage infiltration in both Spike-1(+) and Spike-1(−) lungs (p < 0.0001), and a macrophage shift with important down-regulation of GAL-3(+) alveolar macrophages associated with Spike-1 persistence (p < 0.05), in favor of CD163(+) myeloid derived monocyte-macrophages. Data show that TLR-4 expression induces a persistent activation of the inflammation, with inefficient resolution, and pathological macrophage shift, thus explaining one of the mechanisms of lethal COVID-19.
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Chen, L., Y. Suzuki, and E. F. Wheelock. "Interferon-gamma synergizes with tumor necrosis factor and with interleukin 1 and requires the presence of both monokines to induce antitumor cytotoxic activity in macrophages." Journal of Immunology 139, no. 12 (December 15, 1987): 4096–101. http://dx.doi.org/10.4049/jimmunol.139.12.4096.
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Abstract Small concentrations of recombinant murine interferon-gamma (MuIFN-gamma), recombinant human interleukin 1 (HuIL-1), and recombinant murine tumor necrosis factor (MuTNF), added separately to cultures of thioglycolate-elicited peritoneal macrophages, produced no cytotoxic activity against L5178Y cells, a tumor cell line which is resistant to the direct toxic effects of these cytokines, either alone or in combination. However, small concentrations of MuIFN-gamma when combined with small concentrations of either HuIL-1 or MuTNF activated these macrophages to produce cytotoxic effects against L5178Y cells; small concentrations of HuIL-1 and MuTNF in combination had no macrophage activating activity. Specific antibody to MuTNF blocked the macrophage-activating synergistic effects of MuIFN-gamma + HuIL-1, and specific antibody to HuIL-1 blocked the macrophage-activating activity of MuIFN-gamma + MuTNF, indicating that MuTNF was induced in macrophage cultures treated with MuIFN-gamma + HuIL-1, and that murine IL-1 was induced in macrophage cultures treated with MuIFN-gamma + MuTNF. These results indicate that all three cytokines are required for induction of antitumor cytotoxic activation of macrophages. Experiments with a concentration of MuIFN-gamma which alone could activate macrophages revealed that both MuTNF and murine IL-1 were required for this activation. The demonstration that small concentrations of these three cytokines can act synergistically, but not separately, to activate macrophages indicates the importance of cytokine combinations in immunoregulation and in anti-tumor cell-mediated immune responses.
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Mantuano, Elisabetta, Pardis Azmoon, Coralie Brifault, Michael A. Banki, Andrew S. Gilder, Wendy M. Campana, and Steven L. Gonias. "Tissue-type plasminogen activator regulates macrophage activation and innate immunity." Blood 130, no. 11 (September 14, 2017): 1364–74. http://dx.doi.org/10.1182/blood-2017-04-780205.
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Key Points Tissue-type plasminogen activator inhibits the activity of the innate immune system in macrophages in vitro and in vivo in mice. Suppression of macrophage proinflammatory responses by tPA requires the NMDA receptor.
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Liang, Yan, Xiaoli Sun, Mingjie Wang, Qingmiao Lu, Mengru Gu, Lu Zhou, Qing Hou та ін. "PP2Acα promotes macrophage accumulation and activation to exacerbate tubular cell death and kidney fibrosis through activating Rap1 and TNFα production". Cell Death & Differentiation 28, № 9 (1 травня 2021): 2728–44. http://dx.doi.org/10.1038/s41418-021-00780-5.
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AbstractMacrophage accumulation and activation play an essential role in kidney fibrosis; however, the underlying mechanisms remain to be explored. By analyzing the kidney tissues from patients and animal models with kidney fibrosis, we found a large induction of PP2Acα in macrophages. We then generated a mouse model with inducible macrophage ablation of PP2Acα. The knockouts developed less renal fibrosis, macrophage accumulation, or tubular cell death after unilateral ureter obstruction or ischemic reperfusion injury compared to control littermates. In cultured macrophages, PP2Acα deficiency resulted in decreased cell motility by inhibiting Rap1 activity. Moreover, co-culture of PP2Acα−/− macrophages with tubular cells resulted in less tubular cell death attributed to downregulated Stat6-mediated tumor necrosis factor α (TNFα) production in macrophages. Together, this study demonstrates that PP2Acα promotes macrophage accumulation and activation, hence accelerates tubular cell death and kidney fibrosis through regulating Rap1 activation and TNFα production.
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Yamamoto, N., VR Naraparaju, and PJ Orchard. "Defective lymphocyte glycosidases in the macrophage activation cascade of juvenile osteopetrosis." Blood 88, no. 4 (August 15, 1996): 1473–78. http://dx.doi.org/10.1182/blood.v88.4.1473.bloodjournal8841473.
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Generation of macrophage-activating factor requires a precursor protein, Gc protein (serum vitamin D3-binding protein), as well as participation of beta-galactosidase of inflammation-primed B lymphocytes and sialidase of T lymphocytes. The treatment of human peripheral blood mononuclear cells with an inflammatory lysophospholipid induced beta-galactosidase and sialidase activity of lymphocytes, leading to the generation of macrophage-activating factor and activation of monocytes/macrophages. However, lysophospholipid treatment of peripheral blood mononuclear cells from three infantile patients with osteopetrosis resulted in no significant activation of monocytes/macrophages. The lysophospholipid-inducible beta- galactosidase activity of B lymphocytes as well as that of the sialidase of T lymphocytes was found to be defective in these patients.
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Vieira, Pedro, Angela Castoldi, Pratik Aryal, Kerry Wellenstein, Mark Yore, Odile Peroni, and Barbara Kahn. "CTLA4-Ig treatment improves RBP4-induced adipose tissue inflammation and insulin resistance triggered by MyD88, JNK, ERK and p38 pathways (IRC8P.443)." Journal of Immunology 194, no. 1_Supplement (May 1, 2015): 129.7. http://dx.doi.org/10.4049/jimmunol.194.supp.129.7.
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Abstract Adipose tissue (AT) inflammation and impaired insulin action is a major cause of type 2 diabetes. RBP4 is an adipocyte- and liver-derived protein that has an important role in insulin resistance, metabolic syndrome and AT inflammation. RBP4 elevation causes AT inflammation by activating innate immunity that elicits an adaptive immune response. Our aims are to determine the signaling pathways involved in RBP4-induced macrophage activation and the resulting antigen presentation and Th1 polarization and whether the blockade of antigen presentation improves AT inflammation and insulin resistance. RBP4-overexpressing mice (RBP4-Ox) are insulin resistant and glucose intolerant and have increased AT macrophage and Th1 cell infiltration. In RBP4-Ox, AT macrophages display enhanced JNK, ERK and p38 phosphorylation, and in vitro inhibition of these pathways reduces macrophage activation and macrophage-induced CD4 T cell proliferation and Th1 polarization. Moreover, macrophages obtained from MyD88 knockout mice and activated with RBP4 do not secrete TNF, IL12 and IL-1b and fail to induce CD4 T cell proliferation and Th1 polarization. Treatment of RBP4-Ox mice with CLTA4-Ig reduces AT inflammation and improves insulin resistance. Thus, RBP4 causes insulin resistance, at least partly, through MyD88 pathway and downstream by activating JNK, ERK and p38 pathways. These pathways induce macrophage activation and Th1 polarization, which can be blocked by inhibiting antigen presentation.
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JAWOROWSKI, Anthony, Elizabeth CHRISTY, Permeen YUSOFF, Robert BYRNE, and John A. HAMILTON. "Differences in the kinetics of activation of protein kinases and extracellular signal-related protein kinase 1 in colony-stimulating factor 1-stimulated and lipopolysaccharide-stimulated macrophages." Biochemical Journal 320, no. 3 (December 15, 1996): 1011–16. http://dx.doi.org/10.1042/bj3201011.
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To determine the relevance of mitogen-activated protein kinase activity to macrophage proliferation, we measured the stimulation of myelin basic protein (MBP) kinase and extracellular signal-related protein kinase (ERK) activity in a macrophage cell line (BAC1.2F5), bone marrow-derived macrophages (BMM) and resident peritoneal macrophages (RPM). By using an ‘in-gel’ MBP kinase assay the activities of renaturable MBP kinases were detected, including several with molecular masses similar to those of ERK-1 and ERK-2. These represented a minor fraction of total activity and were not activated to an appreciable extent by colony-stimulating factor 1 (CSF-1). By using a sensitive and specific immune-complex kinase assay, activation of ERK-1 by CSF-1 and lipopolysaccharide (LPS) was demonstrated. Two kinetically distinct pathways of ERK-1 activation by CSF-1 were resolved, with peak activations occurring at 5 and 15 min. The kinetics and degree of activation were similar in BMM, BAC1.2F5 cells and RPM. LPS activated ERK-1 with a single peak at 10–15 min, corresponding to the later peak of activation by CSF-1. Thus there was no strict correlation between ERK activation and macrophage proliferation.
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Bian, Zhen, Lei Shi та Yuan Liu. "Phagocytic plasticity of macrophage towards healthy self cells: inflammatory activation elicit self-attacking phenotype in macrophages lacking SIRPα-CD47 restraint". Journal of Immunology 198, № 1_Supplement (1 травня 2017): 154.7. http://dx.doi.org/10.4049/jimmunol.198.supp.154.7.
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Abstract The interaction between macrophage signal-regulatory protein alpha (SIRPα) and its ligand CD47 serves as a critical self-recognition mechanism, in which their interaction triggers inhibitory signaling via SIRPα cytoplasmic ITIMs and prevent macrophage phagocytosis toward self-cells. Despite this mechanism being suggestively imperative, CD47−/− mice demonstrate no, or only mild, macrophage phagocytosis toward self-cells, suggesting additional activation and inhibitory mechanisms controlling macrophage behavior. Studying our recently established SIRPα −/− mice, as well as CD47−/− mice, we identify that macrophage phagocytosis toward self cells requires activation by inflammatory cytokines/factors. Ex vivo phagocytosis assays demonstrate that macrophages from SIRPα −/− or CD47−/−, and even WT mice, are generally incompetent to attack self-cells, which bear no ‘eat-me’ signal and thus do not activate macrophage phagocytosis. However, treating these macrophages with IL-17, IL-6, IL-1β, TNFα and TLR agonists, but not IFNγ, dramatically initiates potent phagocytosis toward self-cells, for which only the CD47-SIRPα interaction restrains. Mechanistic studies suggest that a PKC-Syk-mediated signaling pathway, to which IL-10 conversely inhibits, is required for activating macrophages toward self cells. Application of activated SIRPα −/− macrophages in targeting CD47-expressing cancer cells also display potent eradication of B16, LLC, MC38, and EL4 cancer cells. These findings significantly expand our knowledge of macrophage phagocytic plasticity under different conditions and also provide insights into strategies for enhancing transplantation tolerance and macrophage-based cancer eradication.
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Esparza, I., D. Mannel, A. Ruppel, W. Falk та PH Krammer. "Interferon γ and lymphotoxin or tumor necrosis factor act synergistically to induce macrophage killing of tumor cells and schistosomula of schistosoma mansoni". Journal of Experimental Medicine 166, № 2 (1 серпня 1987): 589–94. http://dx.doi.org/10.1084/jem.166.2.589.
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Macrophages play a crucial role in the defense against tumors and parasites. Activation of tumoricidal and microbicidal effector mechanisms requires stimulation of macrophages with macrophage-activating factors (MAF). One such MAF is interferon γ (IFN-γ). In some assays, substantial activity of IFN-γ on murine macrophages, however, is only observed in synergy with lipopolysaccharide (LPS) or other cytokines (1). In addition, certain cytokines have been shown to induce monocyte or macrophage activation in the absence of IFN-γ (2-5). We previously described lymphokines in the supernatant of a murine T cell clone that synergized with IFN-γ in the induction of tumoricidal and schistosomulicidal murine macrophages (1). We called this lymphokine(s) macrophage cytotoxicityinducing factor 2 (MCIF2)(1). A candidate for MCIF2 was lymphotoxin (LT), because the T cell clone supernatant contained high amounts of LT. LT is functionally homologous and structurally related to the macrophage product tumor necrosis factor (TNF). Therefore, we tested whether recombinant (r) LT or rTNF can function as MAF. We report here that rLT or rTNF synergize with rIFN-γ in the induction of tumoricidal and schistosomulicidal murine macrophages.
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Llauradó Maury, Gabriel, Humberto J. Morris-Quevedo, Annick Heykers, Ellen Lanckacker, Davie Cappoen, Peter Delputte, Wim Vanden Berghe, Zelene Salgueiro, and Paul Cos. "Differential Induction Pattern Towards Classically Activated Macrophages in Response to an Immunomodulatory Extract from Pleurotus ostreatus Mycelium." Journal of Fungi 7, no. 3 (March 11, 2021): 206. http://dx.doi.org/10.3390/jof7030206.
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Pleurotus ostreatus mushroom preparations have been investigated because of their ability to modulate the immune function. However, there is still no consensus regarding the activation and polarizing effect on macrophages by Pleurotus-derived bioproducts. This study examined the immune-activating effect of a mycelium-derived P. ostreatus aqueous extract (HW-Pm) on macrophage functions, by means of the determination of nitric oxide (NO) production, the mRNA expression of inducible nitric oxide synthase (iNOS), Arginase-1 and FIZZ and the cytokine levels. The phagocytic activity and the activation of NF-κB in U937 reporter cells were also investigated. No cytotoxicity was observed in macrophages treated with HW-Pm (IC50 > 1024 μg/mL) by the resazurin test. HW-Pm induced high levels of NO production and iNOS expression in macrophages. In contrast, HW-Pm did not induce Arginase-1 and FIZZ mRNA expressions. The mushroom extract increased TNF-α and IL-6 production and the phagocytic function in murine macrophages. It also stimulated the activation of the NF-κB promoter. The P. ostreatus mycelium extract has a potential application as a natural immune-enhancing agent, by targeting macrophage activation towards the classically activated subset and stimulating macrophage-mediated innate immune responses.
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Leu, R. W., A. Q. Zhou, B. J. Shannon, and M. J. Herriott. "Inhibitors of C1q biosynthesis suppress activation of murine macrophages for both antibody-independent and antibody-dependent tumor cytotoxicity." Journal of Immunology 144, no. 6 (March 15, 1990): 2281–86. http://dx.doi.org/10.4049/jimmunol.144.6.2281.
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Abstract The inhibitors of C1q biosynthesis and secretion, 3,4-dehydro-DL-proline (DHP) and 2,2'-dipyridyl, were previously shown to suppress murine macrophage FcR-dependent phagocytosis and cytolysis of IgG-opsonized RBC targets. Inasmuch as non-antibody macrophage activators also bind C1q to initiate C1 activation, we determined the effects of these same inhibitors of C1q biosynthesis on activation of macrophages for antibody-independent, nonspecific tumor cytotoxicity by lipid A and a variety of other non-antibody activators. Preexposure of mouse inflammatory peritoneal macrophages to either DHP (0.5 to 2.5 mM) or 2,2'-dipyridyl (0.1 to 0.3 mM) for 24 h produced a dose-related suppression of their response to activation by lipid A to mediate tumor cytotoxicity of L1210 mouse leukemia targets. Inhibition of C1q secretion by DHP-treated macrophages was confirmed both by a complement hemolytic assay and by autoradiographic analysis of [35S]methionine-labeled culture supernatants. DHP-treated macrophages were inhibited in their response to direct activation and triggering of IFN-gamma-primed macrophages by lipid A, Poly I:C, and cobra venom factor for tumor cytotoxicity. DHP inhibited macrophage activation for antibody-dependent cellular cytotoxicity of L1210 tumor targets mediated by antitumor target IgG. The addition of exogenous purified C1q (2 micrograms/ml) to macrophages after DHP treatment, reconstituted their response to activation for both antibody-independent and antibody-dependent tumor cytotoxicity. Our results indicate that C1q synthesis and secretion by effector macrophages is a prerequisite for the initiation of their activation by both immune complex and by non-antibody agents that also bind C1q. It now appears that macrophage-derived C1q may act as an auxiliary amplification signal for autocrine-like modulation of the initiation of macrophage activation by both the antibody-dependent and independent pathways.
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Zhao, Yong, Hao Wang, Ming Lu, Xin Qiao, Bei Sun, Weihui Zhang, and Dongbo Xue. "Pancreatic Acinar Cells Employ miRNAs as Mediators of Intercellular Communication to Participate in the Regulation of Pancreatitis-Associated Macrophage Activation." Mediators of Inflammation 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6340457.
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Macrophage activation plays an important role in the inflammatory response in acute pancreatitis. In the present study, the activation of AR42J pancreatic acinar cells was induced by taurolithocholate treatment. The results showed that the culture medium from the activated AR42J cells significantly enhanced NFκB activation in the macrophages compared to that without taurolithocholate treatment. Additionally, the precipitates obtained from ultracentrifugation of the culture media that were rich in exosomes were markedly more potent in activating macrophages compared with the supernatant fraction lacking exosomes. The results indicated that the mediators carried by the exosomes played important roles in macrophage activation. Exosomal miRNAs were extracted and examined using microarrays. A total of 115 differentially expressed miRNAs were identified, and 30 showed upregulated expression, while 85 displayed downregulated expression. Target genes of the differentially expressed miRNAs were predicted using TargetScan, MiRanda, and PicTar software programs. The putative target genes were subjected to KEGG functional analysis. The functions of the target genes were primarily enriched in MAPK pathways. Specifically, the target genes regulated macrophage activation through the TRAF6-TAB2-TAK1-NIK/IKK-NFκB pathway. As the mediators of signal transduction, miRNAs and their predicted target mRNAs regulate every step in the MAPK pathway.
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Tekin, Cansu, Hella L. Aberson, Cynthia Waasdorp, Gerrit K. J. Hooijer, Onno J. de Boer, Frederike Dijk, Maarten F. Bijlsma, and C. Arnold Spek. "Macrophage-secreted MMP9 induces mesenchymal transition in pancreatic cancer cells via PAR1 activation." Cellular Oncology 43, no. 6 (August 18, 2020): 1161–74. http://dx.doi.org/10.1007/s13402-020-00549-x.
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Abstract Purpose Targeting tumor-infiltrating macrophages limits progression and improves chemotherapeutic responses in pancreatic ductal adenocarcinoma (PDAC). Protease-activated receptor (PAR)1 drives monocyte/macrophage recruitment, and stromal ablation of PAR1 limits cancer growth and enhances gemcitabine sensitivity in experimental PDAC. However, the functional interplay between PAR1, macrophages and tumor cells remains unexplored. Here we address the PAR1-macrophage-tumor cell crosstalk and assess its contributions to tumor progression. Methods PAR1 expression and macrophage infiltration were correlated in primary PDAC biopsies using gene expression datasets and tissue microarrays. Medium transfer experiments were used to evaluate the functional consequences of macrophage-tumor cell crosstalk and to assess the contribution of PAR1 to the observed responses. PAR1 cleavage assays were used to identify a macrophage-secreted PAR1 agonist, and the effects of candidate proteases were assessed in medium transfer experiments with specific inhibitors and/or recombinant agonist. Results PAR1 expression correlates with macrophage infiltration in primary PDACs, and macrophages induce mesenchymal transition of PDAC cells through PAR1 activation. Protease profiling identified macrophage-secreted matrix metalloprotease 9 (MMP9) as the relevant PAR1 agonist in PDAC. PAR1 and/or MMP9 inhibition limited macrophage-driven mesenchymal transition. Likewise, preventing mesenchymal transition by silencing ZEB1 or by pharmacological inhibition of the MMP9/PAR1 axis significantly reduced the ability of tumor cells to survive the anti-tumor activities of macrophages. Conclusion Macrophages secrete MMP9, which acts upon PDAC cell PAR1 to induce mesenchymal transition. This macrophage-induced mesenchymal transition supports the tumor-promoting role of macrophage influx, explaining the dichotomous contributions of these immune cells to tumor growth.
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Nedvetzki, Shlomo, Stefanie Sowinski, Robert A. Eagle, James Harris, Frédéric Vély, Daniela Pende, John Trowsdale, Eric Vivier, Siamon Gordon, and Daniel M. Davis. "Reciprocal regulation of human natural killer cells and macrophages associated with distinct immune synapses." Blood 109, no. 9 (January 11, 2007): 3776–85. http://dx.doi.org/10.1182/blood-2006-10-052977.
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AbstractNatural killer (NK) cells directly lyse tumor or viral-infected cells but also an important role for NK cell cytotoxicity in regulating the extent of immune responses is emerging. Here, we show that autologous human macrophages activated NK cell proliferation and cytokine secretion, increased expression of activating receptors, and primed NK cell cytotoxicity against susceptible target cells. Ligation of NK cell 2B4, and not NKp30 (known to be important for DC-mediated NK cell activation), is critical for this macrophage-mediated NK cell activation. Reciprocally, however, NK cells regulated macrophage activity by directly killing macrophages stimulated by high doses of LPS. Cytolysis was triggered by NKG2D recognition of stress-inducible class I major histocompatibility complex (MHC)–like ligands on macrophages: high doses of LPS induced transcription and surface expression of ULBP1, ULBP2, and ULBP3 and surface expression of constitutively transcribed MICA. Thus, these data suggest a new function for NK cell cytotoxicity in eliminating overstimulated macrophages. Additionally, these interactions define, for the first time, 2 distinct activating NK cell synapses: lytic and nonlytic. Triggering NK cell proliferation and cytokine secretion, but not cytolysis, specifically associated with synaptic accumulation of macrophage F-actin and NK cell 2B4, while macrophages were killed when NK cell F-actin and macrophage ICAM-1 accumulated around a central cluster of NK cell NKG2D/DAP10.
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Maniecki, Maciej Bogdan, Mette Munk Lauridsen, Troels Bygum Knudsen, Jesper Stentoft, Bjarne Kuno Møller, Søren Kragh Moestrup, and Holger Jon Møller. "A Macrophage Activation Switch (MAcS)-Index for Assessment of Monocyte/Macrophage Activation." Blood 112, no. 11 (November 16, 2008): 3550. http://dx.doi.org/10.1182/blood.v112.11.3550.3550.
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Abstract BACKGROUND: The monocyte/macrophage system plays important roles in host defense, regulation of immune responses, tissue repair, neovascularization, and inflammation. These diverse roles are performed by specific subpopulations of macrophages that are differently activated by surrounding stimuli, simplified by the M1-M2 dichotomy of classically activated (M1), pro-inflammatory cells and alternatively activated (M2), anti-inflammatory cells. Macrophages, however, display a large degree of flexibility and are able to switch between activation states (1) The hemoglobin scavenger receptor CD163 is expressed exclusively on monocytes and macrophages, and its expression is strongly induced by anti-inflammatory stimuli like IL10 and glucocorticoid, making CD163 an ideal M2 macrophage marker (2) Furthermore a soluble variant of CD163 (sCD163) is shed from the cell surface to plasma by protease mediated cleavage of the receptor. The shedding of sCD163 is dependent on a pro-inflammatory signal such as toll-like receptor (TLR) activation by LPS (3) These unique properties led us to investigate whether an index of combined soluble- and monocyte membrane CD163 could be used as a surrogate marker for macrophage activation. MATERIALS AND METHODS: Blood sample were obtained from 53 patients with malignant hematological disease and 74 healthy individuals. The cellular (mCD163) and soluble (sCD163) CD163 expression were measured by flow cytometry and ELISA respectively. In addition, blood mRNA expression of inflammatory markers (IL-1β, IL-6, IL-8, IL-10, and TNF-α) was determined by RT-qPCR. Normalized values of sCD163 and mCD163 were calculated by dividing each value by the median value of the healthy population. The MAcS-index was then calculated as the ratio between normalized sCD163 and normalized mCD163. A MAcS-index > 1 indicates relative increase in sCD163 as compared to mCD163, suggested to reflect a predominant M1 activation. RESULTS AND DISCUSSION: The MAcS-index of healthy individuals clustered around 1 (2.5–97.5 percentile: 0.28–3.11), whereas the MAcS-index of the patients varied from 0.06 to 5139, with 4% below the 2.5 % limit of healthy individuals, and 60% above the 97.5 upper limit of healthy individuals. The MAcS-index in infected patients (with assumed M1 activation) was clearly elevated: The index was significantly higher in patients with clinical signs of infection (median: 9.01; range: 1.41–3490) and patients in antibiotic therapy (median: 9.74; range: 0.91–5139) compared to non-infected patients (median: 2.53; range: 0.058–551.5, p<0.05) and non-treated patients (median: 0.97; range: 0.058– 450.8, p<0.0001), respectively. In contrast, patients in glucocorticoid treatment (assumed to drive an M2 activation phenotype) had significantly lower index (median: 1.1; range: 0.058–551) than patients without glucocorticoid treatment (median: 9.4; range: 0.57– 3490), p<0.05. mRNA expression analysis revealed that patients with MAcS-index above upper reference limit expressed higher levels of IL-1β, IL-6, IL-8, and TNF-α compared to patients with MAcS-index within reference range. Patients with malignant myeloma (median: 0.89; range: 0.63–1.51) had significantly lower MAcS-index than patients with AML (median: 20.71; range: 0.57–2214) (p<0.005) and lymphoma (median: 4.34; range 0.058–5139) (p<0.01), suggesting a differentiation towards an anti-inflammatory state. CONCLUSION: We present a CD163-derived macrophage activation switch (MAcS)- index, which seems able to differentiate between (predominantly) pro-inflammatory and anti-inflammatory macrophage activation. The index needs further validation, however, may be very useful for monitoring diseases with macrophage involvement and response to therapeutic interventions.
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Roa-Vidal, Natalia, Adriana S. Rodríguez-Aponte, José A. Lasalde-Dominicci, Coral M. Capó-Vélez, and Manuel Delgado-Vélez. "Cholinergic Polarization of Human Macrophages." International Journal of Molecular Sciences 24, no. 21 (October 29, 2023): 15732. http://dx.doi.org/10.3390/ijms242115732.
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Macrophages serve as vital defenders, protecting the body by exhibiting remarkable cellular adaptability in response to invading pathogens and various stimuli. These cells express nicotinic acetylcholine receptors, with the α7-nAChR being extensively studied due to its involvement in activating the cholinergic anti-inflammatory pathway. Activation of this pathway plays a crucial role in suppressing macrophages’ production of proinflammatory cytokines, thus mitigating excessive inflammation and maintaining host homeostasis. Macrophage polarization, which occurs in response to specific pathogens or insults, is a process that has received limited attention concerning the activation of the cholinergic anti-inflammatory pathway and the contributions of the α7-nAChR in this context. This review aims to present evidence highlighting how the cholinergic constituents in macrophages, led by the α7-nAChR, facilitate the polarization of macrophages towards anti-inflammatory phenotypes. Additionally, we explore the influence of viral infections on macrophage inflammatory phenotypes, taking into account cholinergic mechanisms. We also review the current understanding of macrophage polarization in response to these infections. Finally, we provide insights into the relatively unexplored partial duplication of the α7-nAChR, known as dup α7, which is emerging as a significant factor in macrophage polarization and inflammation scenarios.
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Yamamoto, N., D. D. Lindsay, V. R. Naraparaju, R. A. Ireland, and S. N. Popoff. "A defect in the inflammation-primed macrophage-activation cascade in osteopetrotic rats." Journal of Immunology 152, no. 10 (May 15, 1994): 5100–5107. http://dx.doi.org/10.4049/jimmunol.152.10.5100.
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Abstract Macrophages were activated by administration of lysophosphatidylcholine (lyso-Pc) or dodecylglycerol (DDG) to wild-type rats but not in osteopetrotic (op) mutant rats. In vitro treatment of wild-type rat peritoneal cells with lyso-Pc or DDG efficiently activated macrophages whereas treatment of op mutant rat peritoneal cells with lyso-Pc or DDG did not activate macrophages. The inflammation-primed macrophage activation cascade in rats requires participation of B lymphocytes and vitamin D binding protein (DBP). Lyso-Pc-inducible beta-galactosidase of wild-type rat B lymphocytes can convert DBP to the macrophage-activating factor (MAF), whereas B lymphocytes of the op mutant rats were shown to be deficient in lyso-Pc-inducible beta-galactosidase. DBP is conserved among mammalian species. Treatment of human DBP (Gc1 protein) with commercial glycosidases yields an extremely high titrated MAF as assayed on mouse and rat macrophages. Because the enzymatically generated MAF (GcMAF) bypasses the role of lymphocytes in macrophage activation, the op mutant rat macrophages were efficiently activated by administration of a small quantity (100 pg/rat) of GcMAF. Likewise, in vitro treatment of op rat peritoneal cells with as little as 40 pg GcMAF/ml activated macrophages.
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TAVARES, ALDO, and ANAMELIA BOCCA. "Dectin-1 restores macrophage anti-Cryptococcus neoformans activity." Journal of Immunology 196, no. 1_Supplement (May 1, 2016): 60.21. http://dx.doi.org/10.4049/jimmunol.196.supp.60.21.
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Abstract The interaction between macrophages and Cryptococcus neoformans (Cn) can result in fungal killing or intracellular replication. The macrophage optimal response requires the specific recognition of fungal molecular structures by a variety of pattern-recognition receptors (PRRs) receptors, mainly TLRs and CLRs.. We report that zymosan (b-glucan)-stimulated macrophages enhanced the antifungal activity against Cn. This activity depends primarily on Dectin-1 activation, with minor contribution of complement receptor 3 and/or TLR2. b-glucan-stimulation also up-regulates macrophage genes associated with an effective immune response, activation of caspase 1, enhanced IL-1b secretion and phagossome acidification. Hence, macrophage permissiveness to Cn intracellular replication is a consequence of interference by the capsule in the recognition between cell wall antigens and PPRs. Our results reveal a new role for the capsule in virulence by establishing that it prevents macrophage activation and thus prevents control of intracellular infection. Therapeutic approaches that promote macrophage activation through stimulation of Dectin-1 may be useful as adjunctive therapy for cryptococcosis.
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Yamamoto, N., S. Homma, and I. Millman. "Identification of the serum factor required for in vitro activation of macrophages. Role of vitamin D3-binding protein (group specific component, Gc) in lysophospholipid activation of mouse peritoneal macrophages." Journal of Immunology 147, no. 1 (July 1, 1991): 273–80. http://dx.doi.org/10.4049/jimmunol.147.1.273.
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Abstract In vitro treatment of mouse peritoneal cells (mixture of adherent and nonadherent cells) with lysophosphatidylcholine (lyso-Pc) in 10% FCS supplemented medium RPMI 1640 results in a greatly enhanced FcR-mediated phagocytic activity of macrophages. This macrophage-activation process requires a serum factor. Fractionation studies with starch block electrophoresis of fetal calf and human sera revealed that alpha 2-globulin fraction contains a serum factor essential for macrophage activation. To identify the serum factor, human serum was precipitated with 50% saturated ammonium sulfate and fractionated on a Sephadex G-100 column. A protein fraction with a lower m.w. than albumin had the capacity to support activation of macrophages. The active serum factor in this protein fraction was analyzed by immunoabsorption by using rabbit antisera against three major proteins of human alpha 2-globulin. This active serum factor was shown to be a vitamin D3-binding protein (group specific component, Gc). By using a monoclonal anti-Gc-absorbed active column fraction of human serum, we observed no enhanced macrophage activation over the results with serum fraction-free cultivation of lyso-Pc-treated peritoneal cells. Cultivation of lyso-Pc-treated peritoneal cells in a medium containing a low concentration of purified human Gc protein (0.1 to 2.6 ng/ml) produced a greatly enhanced phagocytic activity of macrophages. When purified human Gc protein was used in a serum-free medium for stepwise cultivation of lyso-Pc-treated nonadherent cell types, a macrophage-activating factor was efficiently generated. Therefore, it is concluded that the vitamin D3-binding protein is the essential serum factor for the lyso-Pc-primed activation of macrophages.
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Stunault, Marion I., Gaël Bories, Rodolphe R. Guinamard, and Stoyan Ivanov. "Metabolism Plays a Key Role during Macrophage Activation." Mediators of Inflammation 2018 (December 10, 2018): 1–10. http://dx.doi.org/10.1155/2018/2426138.
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Monocyte and macrophage diversity is evidenced by the modulation of cell surface markers and differential production of soluble mediators. These immune cells play key roles in controlling tissue homeostasis, infections, and excessive inflammation. Macrophages remove dead cells in a process named efferocytosis, contributing to the healthy tissue maintenance. Recently, it became clear that the main macrophage functions are under metabolic control. Modulation of glucose, fatty acid, and amino acid metabolism is associated with various macrophage activations in response to external stimuli. Deciphering these metabolic pathways provided critical information about macrophage functions.
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Tang, Hong, JIn Feng, and Chao Zhang. "The innate-like T cells are required to modulate acute inflammatory response (P1050)." Journal of Immunology 190, no. 1_Supplement (May 1, 2013): 65.26. http://dx.doi.org/10.4049/jimmunol.190.supp.65.26.
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Abstract Macrophages infiltration and activation in myocardium is a pivotal immunopathological lead to hypertensive cardiac micro-injury, but underlying mechanisms remain elusive. We have found that CD8 KO or CD8+ T cells depletion by antibody significantly reduce cardiac pro-fibrotic inflammatory responses induced by angiotensin II (Ang II) infusion, whereas CD8 KO mice reconstituted with CD8+ T cells became sensitive. More importantly, CD8+ T cells are required for macrophage infiltration in myocardium and subsequent activation to express pro-inflammatory cytokines and chemokines, including MCP-1. Furthermore, transwell experiments showed that macrophage activation requires direct contact with activated CD8+ T cells, but with TCR dispensable. TCR-independent activation of macrophage is further confirmed in vivo, where OT-I transgenic mice show a similar cardiac pro-inflammatory response to Ang II as wt mice. Finally, IFNγ seems required for influx and activation of CD8+ T cells in myocardium in response to Ang II, that subsequently activate macrophages in the onset of cardiac inflammation. Thus, TCR-independent innate nature of CD8+ T cells is both necessary and sufficient for macrophage-induced hypertensive cardiac fibrosis. In conclusion, TCR-independent activation of macrophages by CD8+ T cells casts yet a novel innate function of T cells that is required to activate inflammatory response of macrophages to danger signals.
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Maataoui-Belabbes, Hajar, Hanaa Bencharef, Bouchra Oukkache, Abdellah Madani, and Mouna Lamchahab. "Macrophage activation syndrome revealing Hodgkin lymphoma." Annales Africaines de Medecine 17, no. 3 (June 28, 2024): e5728-e5733. http://dx.doi.org/10.4314/aamed.v17i3.15.
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Macrophage activation syndrome is an anatomo-clinical entity due to inappropriate stimulation of macrophages. It can be of primary or secondary origin. Blood diseases responsible for reactive macrophage activation syndrome are mainly T or NK lymphomas. The association with Hodgkin lymphoma is exceptional. We report a case of a young adult whose macrophage activation syndrome revealed Hodgkin lymphoma. The diagnosis of macrophage activation syndrome was assured in the light of compatible clinical, biological, and cytological signs. The etiological diagnosis was guided by the bone marrow biopsy and confirmed by the anatomopathological study of a lymph node biopsy. The prognosis remains more pejorative compared to macrophage activation syndromes related to infections or autoimmune diseases. French title: Un syndrome d’activation macrophagique révélant un lymphome hodgkinien Le syndrome d'activation macrophagique est une entité anatomo-clinique due à une stimulation inappropriée des macrophages. Elle peut être d'origine primaire ou secondaire. Les hémopathies responsables du syndrome d'activation macrophagique sont principalement les lymphomes T ou NK. L'association avec le lymphome hodgkinien est exceptionnelle. Nous rapportons un cas d'un jeune adulte chez qui le syndrome d'activation macrophagique a révélé un lymphome hodgkinien. Le diagnostic du syndrome d'activation macrophagique a été posé devant des arguments cliniques, biologiques et cytologiques compatibles. Le diagnostic étiologique a été guidé par la biopsie ostéomédullaire et confirmé par l'étude anatomopathologique d'une biopsie ganglionnaire. Le pronostic reste plus péjoratif par rapport aux syndromes d'activation macrophagique secondaires aux infections ou aux maladies auto- immunes.
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Jha, Aakanksha, and Erika Moore. "Collagen-derived peptide, DGEA, inhibits pro-inflammatory macrophages in biofunctional hydrogels." Journal of Materials Research 37, no. 1 (December 2, 2021): 77–87. http://dx.doi.org/10.1557/s43578-021-00423-y.
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AbstractMacrophages are innate immune cells that play important roles in wound healing. Particularly, M1 macrophages are considered pro‐inflammatory and promote initial phases of inflammation. Long-term exposure to inflammatory stimuli causes an increase in M1 macrophages, which contributes to chronic inflammation. Activated M1 macrophages have been shown to upregulate integrin α2β1 expression. To interfere with α2β1 binding, we designed a biofunctional hydrogel utilizing a collagen I-derived peptide, DGEA (Asp-Gly-Glu-Ala). We hypothesize that M1 macrophage activation can be reduced in the presence of DGEA. Effects of DGEA on M1 macrophages were studied via soluble delivery and immobilization within poly(ethylene glycol) (PEG) hydrogels. We demonstrate that M1 macrophage activation is reduced both via soluble delivery of DGEA in 2D and via immobilized DGEA in a 3D PEG-DGEA hydrogel. This novel biomaterial can manipulate inflammatory macrophage activation and can be applied to prevent chronic inflammatory conditions via macrophage manipulation. Graphical abstract
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Murray, H. W., G. L. Spitalny, and C. F. Nathan. "Activation of mouse peritoneal macrophages in vitro and in vivo by interferon-gamma." Journal of Immunology 134, no. 3 (March 1, 1985): 1619–22. http://dx.doi.org/10.4049/jimmunol.134.3.1619.
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Abstract To determine the role of IFN-gamma in the activation of resident mouse peritoneal macrophages, crude macrophage-activating lymphokines were incubated with a monoclonal anti-murine IFN-gamma antibody. This treatment abolished the capacity of mitogen-induced lymphokines to enhance either H2O2 release or activity against the intracellular protozoa Toxoplasma gondii and Leishmania donovani. All macrophage-activating factor detected by these assays was also removed by passing the lymphokines over a Sepharose column to which the monoclonal anti-IFN-gamma antibody had been coupled. Therefore, pure murine rIFN-gamma was tested both in vitro and in vivo as a single activating agent. After 48 hr of pretreatment in vitro with 0.01 to 1 antiviral U/ml, macrophage H2O2-releasing capacity was enhanced an average of 6.4-fold; half-maximal stimulation was induced by 0.03 U/ml. Resident macrophages infected with T. gondii half-maximally inhibited parasite replication after 24 hr of preincubation with 0.14 U/ml of rIFN-gamma, and near complete inhibition was achieved by pretreatment with 100 U/ml. Half-maximal leishmanicidal activity was induced by 0.08 U/ml of rIFN-gamma, and 67 to 75% of intracellular L. donovani amastigotes were killed after macrophages were preincubated with 10 to 100 U/ml. Eighteen hours after parenteral injection of rIFN-gamma, peritoneal macrophages displayed a dose-dependent enhancement of H2O2-releasing capacity and antiprotozoal activity. Half-maximal enhancement required 85 to 250 U or rIFN-gamma given i.p. Peritoneal macrophages were also activated by rIFN-gamma injected i.v. and intramuscularly. These results suggest that, in the mouse model, IFN-gamma is likely to be a primary factor within mitogen-induced lymphokines responsible for activating macrophage oxidative metabolism and antiprotozoal activity, and indicate that rIFN-gamma is a potent activator of these effector functions both in vitro and in vivo. These findings provide a rationale for evaluating rIFN-gamma in the treatment of systemic intracellular infections, and indicate that murine models are appropriate for such studies.
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Lodyga, Monika, Elizabeth Cambridge, Henna M. Karvonen, Pardis Pakshir, Brian Wu, Stellar Boo, Melanie Kiebalo та ін. "Cadherin-11–mediated adhesion of macrophages to myofibroblasts establishes a profibrotic niche of active TGF-β". Science Signaling 12, № 564 (15 січня 2019): eaao3469. http://dx.doi.org/10.1126/scisignal.aao3469.
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Macrophages contribute to the activation of fibroblastic cells into myofibroblasts, which secrete collagen and contract the collagen matrix to acutely repair injured tissue. Persistent myofibroblast activation leads to the accumulation of fibrotic scar tissue that impairs organ function. We investigated the key processes that turn acute beneficial repair into destructive progressive fibrosis. We showed that homotypic cadherin-11 interactions promoted the specific binding of macrophages to and persistent activation of profibrotic myofibroblasts. Cadherin-11 was highly abundant at contacts between macrophages and myofibroblasts in mouse and human fibrotic lung tissues. In attachment assays, cadherin-11 junctions mediated specific recognition and strong adhesion between macrophages and myofibroblasts. One functional outcome of cadherin-11–mediated adhesion was locally restricted activation of latent transforming growth factor–β (TGF-β) between macrophage-myofibroblast pairs that was not observed in cocultures of macrophages and myofibroblasts that were not in contact with one another. Our data suggest that cadherin-11 junctions maintain latent TGF-β–producing macrophages and TGF-β–activating myofibroblasts in close proximity to one another. Inhibition of homotypic cadherin-11 interactions could be used to cause macrophage-myofibroblast separation, thereby destabilizing the profibrotic niche.