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At least 19 recordsLinked to original sources
PubMed1975

Interactions between actin, myosin, and an actin-binding protein from rabbit alveolar macrophages. Alveolar macrophage myosin Mg-2+-adenosine triphosphatase requires a cofactor for activation by actin.

The interactions were analyzed between actin, myosin, and a recently discovered high molecular weight actin-binding protein (Hartwig, J. H., and Stossel, T. P. (1975) J. Biol Chem.250,5696-5705) of rabbit alveolar macrophages. Purified rabbit alveolar macrophage or rabbit skeletal muscle F-actins did not activate the Mg2+ATPase activity of purified rabbit alveolar macrophage myosin unless an additional cofactor, partially purified from macrophage extracts, was added. The Mg2+ATPase activity of cofactor-activated macrophage actomyosin was as high as 0.6 mumol of Pi/mg of myosin protein/min at 37 degrees. The macrophage cofactor increased the Mg2+ATPase activity of rabbit skeletal muscle actomyosin, and calcium regulated the Mg2+ATPase activity of cofactor-activited muscle actomyosin in the presence of muscle troponins and tropomyosin. However, the Mg2+ATPase activity of macrophage actomyosin in the presence of the cofactor was inhibited by muscle control proteins, both in the presence and absence of calcium. The Mg2+ATPase activity of the macrophage actomyosin plus cofactor, whether assembled from purified components or studied in a complex collected from crude macrophage extracts, was not influenced by the presence of absence of calcium ions. Therefore, as described for Acanthamoeba castellanii myosin (Pollard, T. D., and Korn, E. D. (1973) J. Biol. Chem. 248, 4691-4697), rabbit alveolar macrophage myosin requires a cofactor for activation of its Mg2+ATPase activity by F-actin; and no evidence was found for participation of calcium ions in the regulation of this activity. In macrophage extracts containing 0.34 M sucrose, 0.5 mM ATP, and 0.05 M KCl at pH 7.0,the actin-binding protein bound F-actin into bundles with interconnecting bridges. Purified macrophage actin-binding protein in 0.1 M KCl at pH 7.0 also bound purified macrophage F-actin into filament bundles. Macrophage myosin bound to F-actin in the absence but not the presence of Mg2+ATP, but the actin-binding protein did not bind to macrophage myosin in either the presence or absence of Mg2+ATP.

Actins↗
PubMed2026

Human iPSC-derived alveolar macrophages reveal macrophage subtype functions of itaconate in M. tuberculosis defense.

Mycobacterium tuberculosis (Mtb) survives within multiple macrophage populations during infection, including alveolar macrophages (AMs) and recruited inflammatory macrophages. In mice, itaconate, produced in macrophages by ACOD1-mediated decarboxylation of aconitate, has direct antimicrobial activity, modulates inflammatory cytokines, and is required for resistance to Mtb infection. The role of itaconate in human macrophages is less clear, and it is unknown whether itaconate mediates distinct effects in macrophage subtypes. Here, we investigated the role of itaconate in macrophages derived from human induced pluripotent stem cells (iPSCs), induced by either GM-CSF to resemble AMs (AM-like cells, hereafter ipAM-Ls) or M-CSF to resemble monocyte-derived macrophages (MDM-like cells, hereafter ipMDM-Ls). Both human macrophage types produced substantially less itaconate than mouse macrophages, and ipAM-Ls produced 4-fold less itaconate than ipMDM-Ls. Surprisingly, ACOD1-deficient ipAM-Ls, but not ipMDM-Ls, were permissive for Mtb growth. Moreover, itaconate functioned to dampen the Mtb-induced inflammatory response in ipMDM-Ls, but not ipAM-Ls, affecting both the type I IFN and TNF pathways. These results indicate that itaconate is involved in human macrophage responses to tuberculosis, with distinct roles in different macrophage subsets. These results also show that genetically tractable iPSC-derived macrophages are a useful model to dissect cellular host-pathogen interactions in human macrophages.

Humans↗
PubMed1979

Fc-receptor-bearing macrophages isolated from hypersensitivity and foreign-body granulomas. Delineation of macrophage dynamics, fc receptor density/avidity and specificity.

Foreign-body and delayed hypersensitivity granulomas were induced in mice; and the dynamics of macrophages isolated from dispersed, 1--4-week-old lesions was delineated. The size and histologic complexity of the lesions increased as shown: adjuvant greater than schistosome egg greater than methylated bovine serum albumin greater than bead. Esterase staining, spreading on glass, and the percentage of Fc-receptor--bearing macrophages present in the various granulomas reflected the same gradient. The Fc receptors were examined by rosetting with rabbit-antibody--SRBC complex (EA). Whereas more than 90% of the population of macrophages of the dermal adjuvant granuloma contained undiminished numbers of receptor-bearing macrophages throughout the 4 weeks, the percentage of macrophages that displayed receptors in pulmonary foreign-body (40%) and delayed hypersensitivity granulomas (70%) peaked at 1 week and subsequently declined. The EA rosetting of the foreign-body and delayed hypersensitivity granuloma macrophages was strongly inhibited by monomeric IgG2a-specific and weakly by aggregated IgG2b-specific mouse myeloma proteins. Also, macrophages of the delayed hypersensitivity granulomas rosetted in higher percentages with SRBCs coupled with monomeric IgC2a than with those coupled with aggregated IgG2b myeloma proteins. Macrophages of the foreign-body lesion did not react with aggregated IgG2b--SRBC. Rosetting with monomeric IgG2a--SRBC or aggregated IgG2b--SRBC could not be cross-inhibited by the myeloma proteins. Both the monomeric IgG2a--SRBC and aggregated IgG2b--SRBC complexes were readily phagocytized. Trypsin treatment of the macrophages inhibited rosetting with EA or myeloma-protein--coupled SRBCs. The display of Fc receptors on the granuloma macrophages seems to be related to the etiology of the lesion and the intensity and duration of the inflammatory reaction.

Animals↗
PubMed1978

Studies on the mechanisms of macrophage activation. I. Destruction of intracellular Leishmania enriettii in macrophages activated by cocultivation with stimulated lymphocytes.

When cultures of normal mouse peritoneal macrophages were infected with the intracellular protozoan parasite Leishmania enrietti, the micro-organism was found to survive intracellularly for several days, apparently without multiplication. However, exposure of infected macrophages to certain stimuli led to rapid parasite killing and digestion, providing a sensitive assay with which the mechanisms of macrophage activation can be studied. Microbicidal activity was induced by incubation of macrophages with syngeneic spleen lymphocytes, which were stimulated either by allogeneic cells in mixed lymphocyte culture (MLC) or by the plant lectin concanavalin A (Con A). Cocultivation with MLCs led to parasite killing within 48-72 h, whereas exposure of infected cells to Con A-stimulated lymphocytes resulted in substantial destruction of the micro-organism within less than 24 h, an effect which was dependent on the presence of thymus-derived lymphocytes and was inhibited by alpha methyl-mannoside. Incubation with Con A-stimulated lymphocytes also led to lysis of part of the macrophage monolayer. However, parasite killing did not result from decreased macrophage survival, as destruction of the micro-organism was highest under culture conditions which were the least detrimental to the phagocytes. Conversely, excess numbers of Con A-stimulated lymphocytes were less efficient at inducing macrophage activation and displayed marked toxicity to the macrophage monolayer. When spleen cells were stimulated by Con A at concentrations above 10 mug/ml, a decrease was noted in the capacity of macrophages to destroy the parasite, probably reflecting a toxicity of the lectin for lymphocytes resulting in impaired activating capacity.

Animals↗
PubMed1979

Analysis of the effects of lipopolysaccharide on macrophages: differential phagocytic responses of C3H/HeN and C3H/HeJ macrophages in vitro.

The phenomenon of lipopolysaccharide (LPS)-induced in vitro macrophage cytotoxicity has been reported by a number of investigators but has often been difficult to reproduce and to quantitate. In this report, we have examined the effect of LPS on the ability of macrophages to ingest 51Cr-labeled, opsonized sheep erythrocytes as a method for examining the direct toxic effects of LPS on macrophages in vitro. By using this assy, we can clearly discriminate between LPS responder C3H/HeN macrophages and LPS nonresponder C3H/HeJ macrophages and demonstrate that LPS induces a profound inhibition of Fc-mediated phagocytosis in LPS responsive macrophages. Furthermore, low concentrations of LPS stimulate phagocytosis in macrophages derived for C3H/HeJ mice. The lipid A moiety of the LPS is responsible for the observed enhancement or inhibition of Fc-mediated phagocytosis. This assay was more sensitive than LPS-induced cytotoxicity, since inhibition of phagocytosis was detectable in cultures of LPS-sensitive macrophages even when cytotoxicity, assessed by trypan blue exclusion, was not. Thus, this assay represents an extremely sensitive method for analyzing the direct effects of LPS on macrophages.

Animals↗
PubMed1979

Macrophages in resistance to rickettsial infection: macrophage activation in vitro for killing of Rickettsia tsutsugamushi.

Rickettsia tsutsugamushi, strain Gilliam, replicates in cultures of resident peritoneal macrophages from BALB/c mice. Macrophage cultures treated with culture supernatants of spleen cells from rickettsial-infected mice stimulated with heat-killed rickettsiae markedly suppressed macrophage infection by rickettsiae. Rickettsiacidal activity of activated macrophages was dependent upon both lymphokine concentration and time of incubation in lymphokines. Treatment of macrophage cultures with lymphokines before exposure to viable rickettsiae resulted in an immediate decrease in percent macrophages infected and numbers of viable intracellular rickettsiae. In these cultures, enhanced intracellular killing was also apparent with further incubation (24 hr). The immediate effect of lymphokine-pretreated macrophages was dissociated from intracellular killing by infecting macrophage cultures first and adding lymphokines after infection. In these cultures, both percent macrophages infected and titers of viable intracellular rickettsiae were dramatically reduced as well.

Animals↗
PubMed1978

Hapten-specific T lymphocyte activation by glutaraldehyde-treated macrophages: an argument against antigen processing by macrophages.

In this communication the effects of glutaraldehyde treatment of trinitrophenyl-(TNP) modified macrophages on their ability to stimulate TNP-specific guinea pig T lymphocyte proliferation were studied. TNP-modified macrophages briefly treated with glutaraldehyde retained much of their ability to stimulate TNP-primed T cells. In contrast, similar treatment of allogeneic macrophages or soluble protein antigen-pulsed syngeneic macrophages completely eliminated their ability to stimulate a mixed leukocyte reaction or protein antigen-specific proliferation, respectively. TNP-modification did not appear to interfere with glutaraldehyde reactivity since macrophages treated with glutaraldehyde before or after TNP-modification stimulated equivalent T cell responses. However, glutaraldehyde treatment of TNP-modified macrophages that had been cultured overnight dramatically reduced their ability to stimulate TNP-specific T cells. Glutaraldehyde-treated TNP-modified macrophages also expressed the same genetic restrictions of T cell activation as untreated stimulators. Thus, T cells primed with syngeneic TNP-modified macrophages were restimulated only by glutaraldehyde-treated TNP-modified syngeneic, but not by allogeneic, macrophages. These results are discussed with respect to the nature of the TNP-specific immunogen recognized by T cells.

Aldehydes↗
PubMed1979

Alveolar macrophages. II. Inhibition of lymphocyte proliferation by purified macrophages from rat lung.

Macrophages were prepared from the lung, peritoneal cavity and blood of normal, unstimulated rats from a number of strains. The macrophages were purified by adherence, and characterized via surface markers, enzyme activity and phagocytic capacity, and subsequently tested for activity in cultures of mitogen-stimulated syngeneic lymphocytes. Peritoneal macrophages and blood monocytes were mildly stimulatory, or ineffective in modulating mitogen-induced DNA synthesis; peritoneal macrophages reconstituted the blastogenic responses of macrophage-depleted lymph node cell cultures to normal limits. In contrast, alveolar macrophages were markedly inhibitory to lymphocyte proliferation; in some instances inhibitory activity was demonstrable when added alveolar macrophages comprised only 0.04% of the total cells in culture. Lymphocyte proliferation induced by T-cell mitogens was more susceptible to this inhibition than was proliferation induced by the B-cell mitogen LPS. Alveolar macrophages recovered from SPF rats, while less in number, exhibited comparable inhibitory activity. These results form part of an emerging picture picture of the normal alveolar macrophage as a potential 'suppressor' of T-cell activity in the lung.

Animals↗
PubMed1978

Ontogeny of macrophage function. I. Phagocytic activity and A-cell activity of newborn and adult mouse peritoneal macrophages.

Phagocytic activity and immune-participating A-cell activity of newborn and adult mouse macrophages were investigated under in vitro conditions. Thioglycollate medium-stimulated newborn (SNB) or adult (SA), and nonstimulated adult (NA) peritoneal macrophages were used. Immune complexes of sheep erythrocytes (SRBC), aldehyde-fixed SRBC, and latex beads were employed in phagocytosis tests. A-cell activity was estimated as the capacity to support primary or secondary responses of macrophage-deprived adult spleen cells to SRBC. Results obtained were: 1) phagocytic activity of NA macrophages was highest and that of SNB macrophages was higher than SA macrophages, 2) no difference was observed in A-cell activity for secondary response among SNB, SA, and NA macrophages, and 3) SNB macrophages were lacking in A-cell activity for primary response. These results suggest that the substantial A-cell function should be evaluated in primary responses, and that the A-cell and pahgocytic functions do not necessarily accompany each other.

Aging↗
PubMed2026

tRNA m1A modification orchestrates STING translation in macrophages to enhance antitumor immunity and CAR-macrophage immunotherapy.

Tumor-associated macrophages (TAMs) play crucial roles in tumor progression. However, the mechanisms underlying the posttranscriptional regulation of TAMs remain largely unknown. Here, we demonstrated that Trmt61a, the "writer" enzyme of tRNA N1-methyladenosine (m1A) modification, is highly expressed in proinflammatory macrophages in tumor microenvironment. We generated conditional knockout (KO) mice for Trmt61a and observed that Trmt61a deletion in macrophages significantly promoted tumor growth. Mechanistically, we identified that m1A maintains the translation of STING, enhances STING-TBK1-IFN-β signaling in macrophages and therefore suppresses tumor cell growth. We further generated TRMT61A-overexpressing human iPSC-derived CAR-macrophage and demonstrated that human TRMT61A effectively promoted antitumor CAR-macrophage therapy in vivo. Collectively, our findings reveal a novel regulatory mechanism of tRNA m1A modification in macrophages, highlighting the antitumor therapeutic potential of targeting tRNA m1A modification in macrophages.

Animals↗
PubMed1979

Augmentation of macrophage complement receptor function in vitro. I. Characterization of the cellular interactions required for the generation of a T-lymphocyte product that enhances macrophage complement receptor function.

The function of complement receptors of mouse peritoneal macrophages was converted in vitro from mediating only attachment of macrophage complement receptor function was achieved by treating freshly explanted macrophages with supernates from cultures containing T lymphocytes and appropriately triggered macrophages. Fc receptor-mediated phagocyctosis by macrophages was required for the production of active supernates, for neither ingestion via the cells' complement receptors nor ingestion via nonimmunologic means was a sufficient stimulus for the macrophages' participation in the generation of supernatant activity. Fc receptor-triggered macrophages interacted by a contact dependent, but histocompatibility independent, mechanism with T lymphocytes, thereby signalling the lymphocytes to elaborate the active product. The possible significance of enhanced macrophage complement receptor function in inflammation, host defense against microbial pathogens, immune complex disease, and neoplasia is discussed.

Animals↗
PubMed1975

Specific macrophage immunity to Sendai virus: macrophage aggregation in vitro with Sendai virus by cytophilic antibodies.

When a 24-h tube culture of rabbit alveolar macrophages was infected with Sendai virus, the rate of infected cells was found to be limited. Even at a multiplicity of infection (MOI) of 500 plaque-forming units per cell, an average of 63% cells was found to synthesize viral antigens stainable by direct immunofluorescence. When the macrophages obtained from rabbits hyperimmunized by an intravenous injection of Sendai virus were infected under the same in vitro conditions, the rate of antigen synthesis averaged a low as 23%. At the time of infection of alveolar macrophages from immunized rabbits (immune macrophages), cell aggregation at an MOI 50 and cell fusion at an MOI 500 were found 24 h after infection, and these reactions were never encountered after the infection of nonimmune macrophages. When the immune macrophages were either pretreated by trypsin or incubated in medium at pH 4.0, the infection no longer caused the aggregation. The supernatant fluid obtained after incubation at pH 4.0 contained neutralizing antibody to Sendai virus. Conversely, when nonimmune macrophages were incubated in the presence of rabbit anti-Sendai virus serum or purified immunoglobulin G, the same aggregation reaction occurred after virus infection. Ultraviolet light-killed Sendai virus could be used as the counterpart of alive virus in the same aggregation reaction. These results suggest that the aggregation reaction of the immune macrophages could be attributed to the presence of specific cytophilic antibodies on their surface.

Antibodies↗
PubMed1978

Electron microscopy of peroxidase and acid phosphatase in leprous and uninfected armadillo macrophages: a macrophage subpopulation contains peroxisomes and lacks bacilli.

Lepromatous tissue from armadillos inoculated 24--36 months earlier with Mycobacterium leprae was obtained for electron microscopic studies. Cytochemically stained lepromas revealed a subpopulation of macrophages containing peroxisomes. These peroxidase reactive macrophages were not infected with bacilli. Acid phosphatase was present in macrophages and many of these were infected with bacilli and contained vacuoles and lipid globules. Within the membrane-bound vacuoles, acid phosphatase surrounded bacilli. However, the reaction product ended abruptly at a 15--40 millimicron thick zone of low electron density surrounding intact bacilli. Acid phosphatase was more intensely reactive and localized less precisely in heavily infected and vacuolated macrophages than in lightly and non-infected cells. The effectiveness of this bacillary barrier and the numerous infected macrophages with substantial acid phosphatase argue against the ability of acid phosphatase to protect host cells from leprosy bacilli. Evidence suggests a protective action of peroxidase or the rapid turnover of macrophages within lepromas. Granular and membranous debris were commonly seen within vacuoles of infected macrophages. A portion of the debris was ultrastructurally similar to bacillary matrix and was nonreactive for peroxidase and acid phosphatase. Following homogenization and centrifugation, similar materials banded with bacilli above 60% sucrose. Another portion of the debris was ultrastructurally similar to host lysosomal matrix and was reactive for acid phosphatase. Results support the concept of dual host and parasitic origins of the debris found in phagolysosomes of infected macrophages. Transparent, oval Epon defects remained eccentric to the majority of intact bacilli in centrifuged fractions. Apparently, an intrinsic property of leprosy produced these Epon defects.

Acid Phosphatase↗
PubMed1977

The role of macrophages in the generation of T helper cells. V. Evidence for differential activation of short-lived T1 and long-lived T2 lymphocytes by the macrophage factors GRF and NMF.

The generation of T helper cells in vitro requires macrophages or macrophage-derived factors such as genetically related macrophage factor (GRF) or nonspecific macrophage factor (NMF). However, there is a basic difference of T helper cell induction when using particulate antigens. The present study demonstrates that this difference is based on the activation of two different T cell subsets. GRF activates short-lived 'T1' cells which amplify the induction of T2 cells, which are the helper cell precursors. Thus, the genetic restriction of T helper cell induction seen with soluble antigen or GRF lies on the level of macrophage or GRF interaction with T1 cells. NMF (or macrophages) and particulate antigens directly activate the helper cell precursor (T2) indicating no requirement for T1-T2 cooperation. The direct activation of the helper cell precursor with particulate antigens does not require histocompatible macrophages or NMF from histocompatible macrophages. The present results may explain some of the discrepancies reported in the literature concerning the genetic requirements and specificity of T cell activation.

Animals↗
PubMed1977

Macrophage activation for tumor cytotoxicity: induction of tumoricidal macrophages by supernatants of PPD-stimulated Bacillus Calmette-Guérin-immune spleen cell cultures.

Resident peritoneal macrophages from normal mice were activated for tumor cytotoxicity in vitro by co-cultivation with BCG1-immune spleen cells and PPD and by incubation with supernatants of PPD-stimulated BCG-immune spleen cell cultures (lymphokine supernatants). Lymphokine activation of macrophages occurred in unfractionated PC suspensions as well as in macrophage monolayers depleted of nonadherent PC. Tumor cytotoxicity by lymphokine-activated macrophages was evident by 3 to 4 hr of culture in active supernatants, reached maximal levels by 8 to 12 hr. and was absent by 20 hr. Continued incubation in lymphokines or even re-exposure after washing did not maintain macrophage cytotoxicity. The capacity of normal resident macrophages to be activated by lymphokines in vitro progressively decreased and was absent by 20 hr in culture. This decrease did not necessarily reflect cell death; macrophage viability as estimated by exclusion of trypan blue or by phagocytic responses did not change over the 20-hr culture period. The short lived nature of both macrophage tumoricidal capacity and capacity of precursor cells to be activated by lymphokines may function as negative feedback mechanisms in immune reactions.

Animals↗
PubMed1977

Specific binding of T lymphocytes to macrophages. II. Role of macrophage-associated antigen.

Peritoneal exudate lymphocytes from immune guinea pigs that bind in vitro to autologous antigen-pulsed macrophages were allowed to proliferate for 1 week to give a population markedly enriched in antigen-specific T cells. This enriched population was then studied with regard to its binding to fresh autologous antigen-pulsed macrophages. Specific binding was not inhibited by a large excess of antigen in the media (5000-fold greater than the amount of antigen associated with the macrophages) either soluble or bound to Sepharose beads, or by coating the antigen-pulsed macrophags with antibody to the exogenous antigen, by reacting a second layer of antibody to the heterologous antibody, or by haptenating the antigen and treating the hapten-antigen macrophage complex with excess anti-hapten antibody. Results of treating antigen-pulsed macrophages with the proteolytic enzymes trypsin and pronase indicate that exogenous antigen is on the macrophage surface, but the experiments failed to prove that the removable antigen is essential for binding. The simplest interpretation of these results is that the T cell receptor is not specific for native exogenous antigen.

Animals↗