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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↗
PubMed1975

The role of macrophages in the generation of T helper cells. III. Influence of macrophage-derived factors in helper cell induction.

Helper cell induction to soluble or particulate antigens in vitro requires the cooperation of T cells and macrophages. A direct contact between macrophages and T cells is not obligatory for this cooperation and factors released from macrophages are as effective in activating T cells as the cells themselves. Two different types of macrophage-derived factors where found. The supernatant obtained from purified macrophages incubated with antigen for several days generates helper cells in absence of macrophages or additional antigen, but only if obtained from macrophages which were identical at the I-A subregion of the H-2 complex as the T cells. This factor was called genetically related macrophages factor (GRF). The other factor(s), which is present in the supernatant obtained from macrophages incubated for several days without antigen, replaces macrophages only if the antigen is particulate. This factor(s), called nonspecific macrophage factor (NMF) is not restricted genetically and is also obtained from allogeneic macrophages. The importance of both these factors in helper cell induction is discussed.

Animals↗
PubMed1975

Studies of the macrophage complement receptor. Alteration of receptor function upon macrophage activation.

We have examined the roles of Fc receptors and complement receptors in mediating the interaction of sensitized sheep erythrocytes (E) with activated and with nonactivated mouse peritoneal macrophages. Both activated and nonactivated macrophages ingest IgG-coated erythrocytes [E(IgG)]; activated cells intest 1.5-2 times as man E(IgG) as do nonactivated macrophages. Thus, there is a quantitative difference in Fc receptor-mediated ingestion between activated and nonactivated macrophages. There is, however, a qualitative difference in function of complement receptors of activated and nonactivated macrophages. Nonactivated macrophages avidly bind complement-coated E [E(IgM)Ia1, but do not ingest them to a significant degree. Activated macrophages, on the other hand, bind and ingest E(IgM)C. The possibility of Fc receptor participation in mediating ingestion of E(IgM)C by activated macrophages was eliminated by blocking Fc receptors with an antimacrophage IgG fraction. Activated macrophages treated with antimacrophage IgG did not ingest E(igG) but did ingest both E(IgM)C AND E(IgM)C. Nonactivated macrophages treated with antimacrophage IgG did not interact at all with E(IgG). These cells bound, but did not ingest, E(IgM)C and E(IgM)C. Complement receptor-mediated ingestion is a marker for macrophage activation and may be physiologically important in the elimination of complement-coated particles.

Animals↗
PubMed1975

Macrophage heterogeneity in receptor activity: the activation of macrophage Fc receptor function in vivo and in vitro.

The Fc receptor activity of single macrophages and of distinct macrophage populations was examined in terms of cellular avidity for IgG antibody by using a rosette assay which permits characterization of receptor activity at the cellular level and quantitation of any changes in such receptor activity. Marked heterogeneity was shown to exist within normal populations of macrophages. Both normal peritoneal and alveolar macrophage populations exhibit a normal or logistic distribution of cellular avidities for IgG antibody. The mean avidity of the peritoneal population, however, was found to be approximately 3 times greater than that of the alveolar population. Moreover, alveolar macrophages possess a range of cellular avidities 3 times greater than that of peritoneal macrophages. Comparison of normal unstimulated peritoneal macrophages and induced inflammatory exudate macrophages revealed a 6-fold increase in the proportion of high avidity cells in the latter population. Normal peritoneal and normal alveolar macrophages were shown to undergo a striking increase in Fc receptor activity in vitro. Under certain conditions of culture these cells acquire the antibody-binding capacity characteristic of high avidity cells in the inflammatory exudate population. Fresh guinea pig serum was shown to prevent this activation of Fc receptor function in vitro. Aged guinea pig serum was somewhat less effective. The serum factor(s) responsible appears to be consumed or exhausted in some way by macrophages. It is heat stable and has a molecular weight of less than 100,000 daltons. Serum IgF was found not to be involved in the effects of fresh serum on receptor activation in vitro. The activation of Fc receptor function described here may facilitate both the presentation of antigen to specific T lymphocytes and the antibody dependent killing of tumor cells by macrophages. Changes in receptor activity of the kind described may thus play an important regulatory role in the induction of an immune response and in the effector mechanisms of immunologic surveillance.

Animals↗
PubMed1976

Correlation of antitumor chemoimmunotherapy with bone marrow macrophage precursor cell stimulation and macrophage cytotoxicity.

The present investigations have assessed the effects of prolonged cyclophosphamide (CY) and Corynebacterium (CP) treatment on the production of bone marrow macrophage precursors [colony-forming cells (CFC)] and on the cytotoxicity of macrophages comprising colonies produced by the CFC. The findings have been correlated with tumor growth in animals receiving the immunochemotherapy. In addition, studies have been directed toward ascertaining whether the administration of CP with CY might lessen the myelosuppressive effects of the latter. Following each consecutive weekly dose of CY (even after as many as 11), there was a significant depression in the number of bone marrow cells (BMC's) but, by the next injection, marrow cellularity had returned to normal. When the number of BMC's was reduced, the proportion of the remaining cells, which consisted of CFC, was increased. Upon reconstitution of the marrow, the proportion of CFC returned to the level of the controls. The total number of CFC in marrow was at no time following CY therapy significantly less than the number in marrow of untreated mice. The addition of CP to the treatment regimen with CY resulted in an absolute as well as relative increase in CFC at all times during administration of the combined therapy, i.e., when there was a depression in total numbers of marrow cells, as well as when marrow restoration had occurred. Although CP stimulated the number of cells entering into differentiation, it failed to affect the total numbers of marrow cells, as well as when marrow restoration had occurred. Although CP stimulated the number of cells entering into differentiation, it failed to affect the total BMC's had been neither increased nor prevented from decreasing, by CP administration, indicating that the use of total cellularity as an index of the CP marrow-sparing effect is without merit. The present results relative to cytotoxicity of macrophages derived from the CFC concur with and extend our previous findings indicating that the cytotoxic property of macrophages originates in its ancestral stem cell or CFC and that factors responsible for increasing the CFC population do not selectively stimulate precursor cells responsible for production of the cytotoxic macrophage. Although the proportion of cytotoxic macrophages was not altered by CP when administered with CY, the absolute number of such cells was increased. Since the increase in macrophage colony production and, consequently, in cytotoxic macrophages correlates with increased inhibition of tumor growth when CP was used with CY, it is suggested that macrophage precursors are the cells of primacy in CP immunopotentiation. Their stimulation, resulting in enhanced cytotoxic macrophage formation, could be responsible for the inhibition of tumor growth observed in our model system. The findings also suggest that when myelosuppression is a limiting factor in the use of a chemotherapeutic agent, the concomitant use of CP may be advantageous.

Animals↗
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↗
PubMed1975

The role of macrophages in the generation of T-helper cells. II. The genetic control of the macrophage-T-cell interaction for helper cell induction with soluble antigens.

Helper cell induction to nonparticle antigens in vitro requires the cooperation of T cells and macrophages, but does not occur if the macrophages are allogenic. The reasons for this were investigated. Malfunction of allogenic macrophages was excluded by cultures with their syngenic T cells; suppressor cell induction was excluded by admixture experiments. Thus, T cells and macrophages only cooperated if they were genetically similar. The genetic locus (loci) involved was mapped. Using congenic lines differing only at the H-2 complex, the genetic control of T-macrophage interaction was localized in the H-2 region. Mice with intra H-2 recombinants were used to map the T-macrophage interaction locus in the I-A region of the H-2 complex (formerly known as poly-D, L-ala-poly-L-lys. Recombinants were also used to exclude the presence of another T-macrophage locus either the K, I-B, or I-C, SS-Slp, or D regions of the H-2 complex. Genetic restrictions for T-macrophage interaction in helper cell induction was shown in mice of the H-2-k, d, b, q, s genotypes as well as in H-2 recombinants. The possible mechanisms and significance of this genetic restriction are discussed.

Amino Acids↗
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↗