Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MACROPHAGES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2006

Low-density lipoprotein modified by macrophage-derived lysosomal hydrolases induces expression and secretion of IL-8 via p38 MAPK and NF-kappaB by human monocyte-derived macrophages.

OBJECTIVE: Modified lipoproteins induce inflammatory reactions in the atherosclerotic arterial wall. We have previously found that macrophages in atherosclerotic lesions secrete lysosomal hydrolases that can modify low-density-lipoprotein (LDL) in vitro to generate "hydrolase-modified LDL" (H-LDL). Here, we studied whether H-LDL exerts inflammatory effects on cultured human macrophages. METHODS AND RESULTS: Using cytokine cDNA arrays, we found that H-LDL induced expression of IL-8, but not of the anti-inflammatory cytokines IL-10 and transforming growth factor (TGF)-beta, in human monocyte-derived macrophages. H-LDL induced rapid phosphorylation of the p38 mitogen-activated protein kinase (MAPK), nuclear translocation of 2 transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1), and time-dependent secretion of IL-8 from the macrophages. Inhibition of MAPKs and of transcription factors showed that p38 MAPK and NF-kappaB, but not ERK1/2, JNK, or AP-1, were crucial for the H-LDL-induced IL-8 secretion from the macrophages. CONCLUSIONS: The results show that by activating p38 MAPK and NF-kappaB, macrophage hydrolases modify LDL into biologically active particles capable of triggering the secretion of IL-8 in macrophages. Thus, activated hydrolase-secreting macrophages in atherosclerotic lesions may sustain a proatherogenic extracellular environment by hydrolyzing LDL and triggering it to act in an autocrine or paracrine fashion to induce IL-8 secretion by the plaque macrophages.

Biological Transport↗
PubMed1994

Essential differences in cholesteryl ester metabolism between human monocyte-derived and J774 macrophages. Evidence against the presence of hormone-sensitive lipase in human macrophages.

Cholesteryl ester-laden macrophages are the hallmark of the fatty streaks that precede arteriosclerotic plaques in humans and experimental animals. This article studies several aspects of cytoplasmic cholesteryl ester metabolism in cultured human monocyte-derived macrophages. Adenosine 3',5'-cyclic monophosphate (cAMP) consistently inhibited cholesteryl ester mobilization from cells that had been loaded with cholesteryl esters by preincubation with acetylated low-density lipoprotein. This effect was observed in both the absence and presence of extracellular cholesterol acceptors as well as with acyl coenzyme A: cholesterol acyltransferase inhibitors. In contrast, dibutyryl cAMP activated cholesteryl ester hydrolysis in J774 macrophages. Since hormone-sensitive lipase is thought to be responsible for the neutral cholesteryl ester hydrolytic activity in several cell types, we looked for the presence of its mRNA in our macrophages by means of reverse transcription coupled to the polymerase chain reaction technique. Hormone-sensitive lipase mRNA was detected in J774 macrophages but not in human monocytes or in human monocyte-derived macrophages. These results demonstrated great differences in cholesteryl ester metabolism between macrophages of different origin. While hormone-sensitive lipase may be responsible for neutral cholesteryl ester hydrolytic activity in J774 macrophages, in human monocyte-derived macrophages it is not; thus, a different and as yet unidentified enzyme must be present.

Base Sequence↗
PubMed1987

Maintenance of the normal rat alveolar macrophage cell population. The roles of monocyte influx and alveolar macrophage proliferation in situ.

We investigated the relative importance of monocyte influx and alveolar macrophage proliferation in maintenance of the alveolar macrophage population in normal rats. Two experimental approaches were used. To detect possible monocyte influx, we radiolabeled blood monocytes by a continuous infusion of tritiated thymidine for 7 days and assayed lavaged alveolar macrophages for radiolabel by autoradiography. Although heavily labeled monocytes occurred in the blood, no heavily labeled cells were detectable among lavaged alveolar macrophages by cohort analysis. To evaluate macrophage proliferation in vivo, we injected normal unlabeled rats with colchicine and examined lavaged alveolar macrophages for arrested mitoses. Mitotic figures were observed among lavaged alveolar macrophages, and calculations at serial times after colchicine injection indicated that 1.83% of alveolar macrophages entered mitosis each day. On the basis of these 2 lines of evidence, we conclude that the alveolar macrophage cell population in normal rats is supported mainly by cellular proliferation in situ rather than direct monocyte influx from the blood compartment.

Animals↗
PubMed2005

GPX-Macrophage Expression Atlas: a database for expression profiles of macrophages challenged with a variety of pro-inflammatory, anti-inflammatory, benign and pathogen insults.

BACKGROUND: Macrophages play an integral role in the host immune system, bridging innate and adaptive immunity. As such, they are finely attuned to extracellular and intracellular stimuli and respond by rapidly initiating multiple signalling cascades with diverse effector functions. The macrophage cell is therefore an experimentally and clinically amenable biological system for the mapping of biological pathways. The goal of the macrophage expression atlas is to systematically investigate the pathway biology and interaction network of macrophages challenged with a variety of insults, in particular via infection and activation with key inflammatory mediators. As an important first step towards this we present a single searchable database resource containing high-throughput macrophage gene expression studies. DESCRIPTION: The GPX Macrophage Expression Atlas (GPX-MEA) is an online resource for gene expression based studies of a range of macrophage cell types following treatment with pathogens and immune modulators. GPX-MEA follows the MIAME standard and includes an objective quality score with each experiment. It places special emphasis on rigorously capturing the experimental design and enables the searching of expression data from different microarray experiments. Studies may be queried on the basis of experimental parameters, sample information and quality assessment score. The ability to compare the expression values of individual genes across multiple experiments is provided. In addition, the database offers access to experimental annotation and analysis files and includes experiments and raw data previously unavailable to the research community. CONCLUSION: GPX-MEA is the first example of a quality scored gene expression database focussed on a macrophage cellular system that allows efficient identification of transcriptional patterns. The resource will provide novel insights into the phenotypic response of macrophages to a variety of benign, inflammatory, and pathogen insults. GPX-MEA is available through the GPX website at http://www.gti.ed.ac.uk/GPX.

Animals↗
PubMed2003

Immunoregulatory role of ocular macrophages: the macrophages produce RANTES to suppress experimental autoimmune uveitis.

Murine experimental autoimmune uveitis (EAU) is a model of human uveitis. Ocular-infiltrating macrophages play a crucial role in the generation of tissue damage in EAU. In fact, several chemokines are actually produced in the inflamed eye. The aim of this study was to elucidate the role of ocular macrophage-derived chemokines in EAU. C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein peptide 1-20, and the EAU severity was scored at multiple time points based on microscopic fundus observations (retinal vascular dilatation and exudates) and histological examinations. The peak inflammatory response was observed 1 wk (day 16) after the beginning of macrophage infiltration to the eye (day 9). Ocular-infiltrating cells were enriched or depleted of macrophages by magnetic beads and analyzed by real-time RT-PCR for chemokine mRNA production. We found that only the macrophage-enriched cells from the eye produced RANTES, and thus proposed that macrophage-derived RANTES facilitated the ocular inflammations. In contrast to our postulate, neutralization of RANTES by specific Ab in vivo on days 9 and 13 exacerbated EAU. We also found that the ratio of ocular CD4/CD8 T cells was markedly increased after treatment. As a result, RANTES neutralization might exacerbate EAU by modulating the type of T cell subsets recruited to the eye. In conclusion, our data provide insight into the immunoregulatory role of macrophages and RANTES in the pathogenesis of ocular inflammation. Not all macrophage-derived chemokines cause local inflammation, since RANTES produced by ocular macrophages appears to suppress EAU.

Adjuvants, Immunologic↗
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↗
PubMed1989

The role of macrophages in the immunoadjuvant action of liposomes: effects of elimination of splenic macrophages on the immune response against intravenously injected liposome-associated albumin antigen.

The primary antibody response to intravenously administered and liposome-associated human serum albumin (HSA) was studied in mice under conditions where no response could be detected against the non-liposome-associated form of the antigen. The positive response against the antigen, entrapped in and/or exposed on the surfaces of liposomes, thus resulted from the adjuvant action of the liposomes. In mice intravenously injected with dichloromethylene diphosphonate (C12MDP) also entrapped in liposomes, all red pulp macrophages, marginal metallophilic macrophages and marginal zone macrophages had disappeared from the spleen 2 days after administration. Twenty-two days after such a treatment red pulp macrophages and marginal metallophilic macrophages had reappeared, but marginal zone macrophages were still absent. In mice injected with liposome-associated HSA at 2 days after treatment with the C12MDP liposomes, anti-HSA responses were severely depressed, but administration of the liposome-associated antigen 22 days after C12MDP liposomes elicited a normal response. These results point to a role of splenic macrophages in the processing of liposome-associated antigens, but marginal zone macrophages, which are located close to the open ends of the white pulp capillaries and thus are the first macrophages to meet the antigens arriving in the marginal zone are not required.

Adjuvants, Immunologic↗
PubMed1989

A role for the macrophage in normal hemopoiesis: III. In vitro and in vivo erythropoietin gene expression in macrophages detected by in situ hybridization.

Macrophages derived from unstimulated and unseparated mouse bone marrow cells cultivated on hydrophobic foils can release hemopoietic regulator molecules into the surrounding medium. To prove that one of these regulators exists in macrophages in vitro, in situ hybridization using a 1.2-kb erythropoietin (Epo) gene probe was employed. The probe was biotinylated and the signal developed using a streptavidin-gold reagent. Observation was performed using reflection-contrast microscopy. The results indicate that from a 98% pure population of macrophages, 34% F4/80 (mouse, macrophage-specific antigenic determinant)-positive macrophages exhibited Epo gene expression. The technique was also applied to normal, steady-state mouse bone marrow in which approximately 10% of the cells are F4/80-positive and of which about 3% demonstrated simultaneous Epo gene expression. As positive control, kidneys from anemic mice were hybridized with the biotin-labeled Epo DNA. A second positive control utilized biotin-labeled actin DNA hybridized to cultured macrophages and normal bone marrow cells. The accumulating information, demonstrating that the unstimulated kidney does not express the Epo gene, indicates that Epo is produced in other areas of the body under normal, steady-state conditions. The present results show that 1) macrophages can express the Epo gene, 2) this function is carried out by a subpopulation of macrophages, and 3) bone marrow macrophages in vivo may be responsible for the Epo production-target cell mechanism evoked by short-range and/or cell-to-cell interactions under normal, steady-state conditions.

Actins↗
PubMed1986

Macrophage colony formation supported by purified CSF-1 and/or interleukin 3 in serum-free culture: evidence for hierarchical difference in macrophage colony-forming cells.

Using a serum-free culture system, we examined murine macrophage colony formation from bone marrow cells cultured in the presence of purified CSF-1, interleukin 3 (IL 3) or a combination of the two factors. CSF-1 supported macrophage and neutrophil-macrophage colony formation, whereas IL-3 supported the formation of various types of single lineage and multilineage colonies. CSF-1 supported more macrophage colonies from bone marrow cells of normal mice than IL 3, whereas in cultures of bone marrow cells of 5-fluorouracil-treated mice, IL 3 supported more macrophage colonies. A combination of CSF-1 and IL 3 resulted in granulocyte-macrophage (GM) colony formation that was equal to or greater than the sum of GM colony formation supported by the factors individually. The combination of CSF-1 and IL 3 resulted in significant increases in the size of both macrophage and neutrophil-macrophage colonies. Similar increases in colony size were observed when CSF-1 was added to cultures five days after incubation of marrow cells with IL 3. These data support the concept that some of the macrophage colony-forming cells that respond to IL 3 are more primitive than those that are sensitive to CSF-1.

Animals↗
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↗
PubMed1982

Macrophages in resistance to rickettsial infections: genetic analysis of susceptibility to lethal effects of Rickettsia akari infection and development of activated, cytotoxic macrophages in A and B10.a mice.

Susceptibility to lethal effects of Rickettsia akari varies among mouse strains. Although most strains are resistant, A/J mice are extremely sensitive (10,000-fold difference in LD50 between resistant and sensitive strains). In contrast to most strains of mice, A/J mice also fail to develop activated, tumoricidal macrophages after any of several in vivo or in vitro treatments. Are susceptibility to R. akari and inability to develop activated, cytotoxic macrophages in the A/J strain causally related traits? Genetic analysis of macrophage tumoricidal activity in responsive B10.A and nonresponsive A mice suggested this trait was controlled by a single, autosomal, dominant gene. Among (F1 X A) backcross mice, the traits for defective macrophage cytotoxicity and abnormal accumulation of macrophages during inflammation (a response controlled by a single, autosomal, dominant gene) segregated independently. Genetic analysis of resistance to R. akari in sensitive A and resistant B10.A mice suggested this trait was also controlled by a single, autosomal, dominant gene. Among (F1 X A) backcross mice, however, traits for defective macrophage cytotoxicity and R. akari resistance segregated independently. Thus, development of activated tumoricidal macrophages, accumulation of macrophages at sites of inflammation, and resistance to the lethal effects of R. akari in A and B10.A mice were each controlled by single, autosomal, dominant, non-H-2-linked genes. However, genes for control of macrophage activation for tumoricidal activity and for resistance to lethal effects of R. akari infection are distinct.

Animals↗
PubMed1982

Ontogeny of 'macrophage' function. III. Manifestation of high accessory cell activity for primary antibody response by Ia+ functional cells in newborn mouse spleen in collaboration with Ia- macrophages.

The ontogenesis of the responsiveness of murine whole spleen cells in the in vitro primary antibody response paralleled not only the development of competent lymphoid cells but also that of the accessory cell (A-cell) activity of spleen adherent cells (SAC). The Ia+ cell content of SAC (and also peritoneal exudate cells) was very low until 2 weeks of age. The phagocytic activity of macrophages in SAC was higher in newborns than in adults, though no significant difference was observed between Ia- and Ia+ macrophages in phagocytic activity. We attempted to reveal a high A-cell activity using cells in newborn spleen by means of our experimental strategy documented previously in adult mice (Inaba, Nakano & Muramatsu, 1981): though neither Ia- macrophage population (Ia- SAC) nor a temporarily adherent spleen cell population containing few phagocytic macrophages (crude non-macrophage cell fraction, CF) serves as an autonomous A-cell source, the collaboration of Ia+ non-macrophage cells in CF with Ia- SAC causes the manifestation of A-cell activity. Adult CF collaborated as well with newborn SAC as with adult Ia- SAC, indicating that newborn Ia- macrophages are functionally comparable with adult Ia- macrophages in the ability to collaborate with Ia+ non-macrophage cells. On the other hand, a high A-cell activity was generated by the combination of adult Ia- SAC with a large number of newborn CF cells, indicating that there exist competent Ia+ cells in newborn spleen, though much fewer than in adult spleen.

Animals↗
PubMed1995

Transforming growth factor-beta stimulates arginase activity in macrophages. Implications for the regulation of macrophage cytotoxicity.

Macrophage arginine metabolism via nitric oxide (NO) synthase and arginase pathways reduces and enhances tumor cell proliferation, respectively. Transforming growth factor-beta (TGF-beta) has been shown to down-regulate the NO synthase pathway. The present study describes the effect of TGF-beta on the arginase pathway. TGF-beta up-regulated arginase activity in rat peritoneal macrophages as assessed by measuring the generation of [14C]urea from [14C]-L-arginine in the presence of NG-monomethyl-L-arginine (L-NMMA). The stimulation, which reached fivefold after a 48-h exposure of macrophages to 10 ng/ml TGF-beta, was due to reduction in Km value of arginase. TGF-beta-induced up-regulation of arginase activity led to the release of more polyamines, mainly putrescine. The role of this up-regulation on macrophage cytotoxicity toward L-929 tumor cells was analyzed in coculture experiments. Macrophages blunted DNA synthesis by L-929 cells as assessed by measuring the incorporation of [3H]TdR into the cells and the proportion of cells in the G2 phase. Addition of TGF-beta in the presence of L-NMMA permitted L-929 cells cocultured with macrophages to resume DNA synthesis. The mechanism responsible for this restoration was the up-regulation of arginase activity rather than the down-regulation of NO synthase activity since TGF-beta in the presence of L-NMMA failed to further reduce NO synthase activity whereas it still enhanced arginase activity; synthetic putrescine (1-10 microM) also blunted macrophage cytotoxicity toward L-929 cells. This is the first evidence that TGF-beta up-regulates arginase activity in macrophages and, hence, limits macrophage-dependent cytostasis.

Animals↗
PubMed1994

Production of cholesterol-enriched nascent high density lipoproteins by human monocyte-derived macrophages is a mechanism that contributes to macrophage cholesterol efflux.

Atherosclerotic lesions have a lipid core containing crystals and liposomes enriched in unesterified cholesterol as well as numerous monocyte-macrophages enriched in cholesteryl ester. Sufficient amounts of plasma-derived high density lipoproteins (HDL) may not reach and efficiently remove the cholesterol deposited in lesion macrophages or in the lipid core of lesions. We examined the potential of human monocyte-macrophages to produce nascent HDL and to solubilize cholesterol derived from interaction of monocyte-macrophages with lipoprotein and non-lipoprotein sources of cholesterol. Monocyte-macrophages produced discoidal (25 +/- 6 nm long and 6 +/- 1 nm wide (mean +/- S.D.)) and vesicular (89 +/- 41 nm in diameter) lipoprotein particles following and during enrichment of macrophages with cholesterol from acetylated low density lipoprotein (AcLDL) or cholesterol crystals. During cholesterol enrichment, discoidal particles progressively accumulated in the medium for up to 6 days. In contrast, vesicles did not increase past 2 days of incubation. Both the discoidal and vesicular lipoprotein particles had a peak density of about 1.09-1.10 g/ml. The discoidal particles contained apolipoprotein E (apoE), whereas the vesicles contained a major protein constituent with a molecular mass of 22,000 daltons. The vesicles did not contain detectable apoE and the 22,000-dalton protein was not the 22,000-dalton thrombolytic fragment of apoE. Following cholesterol enrichment of macrophages with AcLDL or cholesterol crystals, macrophages excreted much of their accumulated cholesterol, even in the absence of exogenously added cholesterol acceptors. Most of this excreted cholesterol was recovered from the culture medium and was carried in the apoE discoidal particles that showed cholesterol enrichment up to a 2:1 unesterified cholesterol to phospholipid molar ratio. The findings suggest that sufficient production of these nascent HDL by macrophages within atherosclerotic lesions should facilitate removal of cellular and extracellular cholesterol, even in the absence of plasma-derived HDL.

Acetylation↗
PubMed1993

Macrophage tropism of feline leukemia virus (FeLV) of subgroup-C and increased production of tumor necrosis factor-alpha by FeLV-infected macrophages.

Erythroid aplasia is induced in cats by feline leukemia virus (FeLV) of subgroup C but not by FeLV of subgroup A. In an investigation of the role of macrophages in FeLV-C-induced diseases, the concentrations of FeLV and tumor necrosis factor-alpha (TNF-alpha) were compared between feline peritoneal macrophages incubated with FeLV of subgroup A or C. FeLV of both subgroups infected macrophages, but expression of FeLV-C was 21-fold higher than FeLV-A in peritoneal macrophages (P = .004). The supernatants of FeLV-C-inoculated macrophage cultures contained significantly higher levels of TNF-alpha (70 +/- 14 U/mL) at 72 hours postincubation compared with FeLV-A-inoculated (38 +/- 8 U/mL) and uninoculated (31 +/- 8 U/mL) cultures. Moreover, a positive correlation was shown between cell-associated FeLV surface glycoprotein gp70 and TNF-alpha expression in FeLV-C-infected macrophages by immunofluorescence (r = .6; P = .001), measured with a computer-assisted, laser-based digital imaging system. The addition of TNF-alpha to a uniform population of FeLV-infected cells (feline embryonic fibroblasts) caused an enhancement of viral expression (P < .05). These results indicate that FeLV-C has tropism for macrophages, FeLV expression is positively correlated with TNF-alpha expression in macrophages, and TNF-alpha enhances FeLV replication in fibroblasts. We suggest that FeLV-C infection of macrophages and secretion of TNF-alpha may be important in hematopoietic suppression in FeLV-C-infected cats.

Animals↗
PubMed1997

Novel elements located at -504 to -399 bp of the promoter region regulated the expression of the human macrophage scavenger receptor gene in murine macrophages.

The expressions of type I and type II macrophage scavenger receptors (MSRs) are highly specific in macrophages and related cell types. Although some reports have described the regulation of MSR gene expression and proposed some cis-elements related to cell-specific expression, the regulation of MSR remains largely unclear. This is due, in part, to an unacceptably low efficiency of transfection into monocyte/ macrophage cells. In the present study, we optimized the conditions of electroporation in murine macrophage (P388D1) cells. The efficiency of electroporation was increased 20-fold compared with previous methods. Using the optimized method, we focused on studying the regulation of the human MSR promoter in macrophages. We presently demonstrate that: a) the proximal -10 to +50 bp human MSR promoter region is necessary for the cell type-specific expression of human MSR; b) the 6.5 kbp upstream sequence suppresses the expression of human MSR; c) a promoter region extending from -504 to -399 bp produced the greatest increase in transcriptional activity; d) macrophage cell-specific transcription factors bind to the region as determined by electrophoretic mobility shift assay (EMSA) and a footprint assay; and e) mutations of the region reduced about 40-75% of the promoter activity in a transfecting assay. We concluded that novel elements located at the -504 to -399 bp region may play an important role in the regulation of the MSR gene expression in macrophages. We speculate that macrophage-specific factors binding to those elements may be responsible for the transcription regulation of the MSR gene in macrophages.

Animals↗
PubMed1992

Cytokine enhancement of complement-dependent phagocytosis by macrophages: synergy of tumor necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor for phagocytosis of Cryptococcus neoformans.

We have examined the regulation of complement dependent phagocytosis by macrophage-activating cytokines. Tumor necrosis factor (TNF)-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF), but not interferon-gamma, interleukin-4 or macrophage-CSF, stimulated ingestion of the encapsulated fungal pathogen Cryptococcus neoformans by resident peritoneal macrophages in vitro. This was dependent upon opsonization of the yeasts with complement, 72 h of incubation with the cytokines for maximum effect, and the obligate involvement of the macrophage CR3 receptor. TNF-alpha and GM-CSF synergized at low concentrations, resulting in dramatic up-regulation of phagocytosis when compared to either cytokine alone. Supernatants from C. neoformans-specific T cells also increased macrophage phagocytic efficiency. Finally, the administration of neutralizing mAb specific for TNF-alpha and GM-CSF increased mortality in C. neoformans-infected mice, and induced the rapid progression of disease with involvement of the brain and meninges. We conclude that TNF-alpha and GM-CSF are potent regulators of complement-dependent phagocytosis by murine macrophages. Macrophage activation with these two cytokines can completely overcome the anti-phagocytic properties of the virulent yeasts. Our results, therefore, implicate TNF-alpha and GM-CSF as important mediators of resistance to encapsulated pathogens such as C. neoformans where ingestion of the organism is a critical process in host resistance.

Animals↗