Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MONOCYTES”

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 811 records · Page 45Linked to original sources
PubMed2004

Paracrine upregulation of monocyte cyclooxygenase-2 by mediators produced by T lymphocytes: role of interleukin 17 and interferon-gamma.

OBJECTIVE: Cyclooxygenase (COX)-2 is an inducible eicosanoid-forming enzyme that is expressed at sites of inflammation. T lymphocytes and monocytes are found in close proximity at sites of inflammation, including synovitis. We investigated whether activated T lymphocytes express COX-2 and whether activated T cells upregulate monocyte COX-2 expression. METHODS: Human T lymphocytes and monocytes were isolated from fresh buffy coats by density gradient separation followed by passage through either nylon wool columns (T lymphocytes) or counter-current elutriation (monocytes). T lymphocytes were stimulated using anti-CD3 and anti-CD28 in a co-culture system with monocytes using transwells, which prevents cell-cell contact, but allows diffusion of soluble mediators. RESULTS: Repeated examination of COX isotypes in resting and stimulated T cells revealed COX-1, but not COX-2. Activated T cells produced a soluble mediator(s) that upregulated monocyte COX-2. Mediator production was inhibited by cyclosporin A. Activated T cells produced interleukin 17 (IL-17) and interferon-g (IFN-g), and in the co-culture IL-17-neutralizing antibodies partially reduced monocyte COX-2 expression, whereas IFN-g-neutralizing antibodies had the opposite effect. Exogenous IL-17 upregulated monocyte COX-2, although concentrations were high compared with those generated by stimulated T cells. By contrast, monocyte COX-2 expression was downregulated when monocytes were treated with IFN-g prior to stimulation with lipopolysaccharide. CONCLUSION: Soluble mediators produced by activated T cells can influence induction of monocyte COX-2, with IL-17 acting as a positive paracrine regulator and IFN-g acting as a negative regulator. In rheumatoid joints, previously observed high concentrations of IL-17 and low concentrations of IFN-g could contribute to T cell-driven upregulation of monocyte COX-2.

Cells, Cultured↗
PubMed1989

Monocyte Fc gamma receptor recognition of cell-bound and aggregated IgG.

Monocyte and macrophage Fc gamma receptors are important components in the recognition of IgG-coated cells and IgG-containing immune complexes. Two proteins have been identified on human peripheral blood monocytes that can function as Fc gamma receptors, Fc gamma RI (70 Kd) and Fc gamma RII (40 Kd). We studied the role of Fc gamma RI and Fc gamma RII on human monocytes by examining their binding of IgG-sensitized cells (human IgG anti-D-coated RBCs and rabbit IgG-sensitized sheep RBCs) and their binding of human trimeric IgG. To examine the function of monocyte Fc gamma RII, we used an anti-Fc gamma RII monoclonal antibody (MoAb) that competes for the Fc gamma RII ligand binding site. Preincubation of monocytes with saturating concentrations of anti-Fc gamma RII MoAb did not alter the recognition of IgG (anti-D)-sensitized human RBCs by monocytes. Furthermore, ligand-binding studies demonstrated that anti-Fc gamma RII antibody altered neither the number nor the affinity of monocyte-binding sites for human IgG trimer. Anti-Fc gamma RII inhibited monocyte binding of rabbit IgG-sensitized sheep RBCs, but only at low ionic strength or temperature when increased numbers of monocyte Fc gamma RII were expressed. At low ionic strength and 4 degrees C, anti-Fc gamma RII also partially inhibited monocyte binding of human trimeric IgG. Thus, monocyte Fc gamma RII does not appear to recognize IgG-sensitized RBCs or trimeric IgG at physiologic temperatures and ionic strength. The data suggest that Fc gamma RI is the primary Fc gamma receptor on monocytes involved in the binding of IgG (anti-D)-sensitized erythrocytes and low mol wt complexes of IgG.

Animals↗
PubMed1989

Monocyte synthesis of thrombospondin. The role of platelets.

Monocytes produce thrombospondin (TSP), a trimeric glycoprotein whose primary function is not yet clear. Platelet-poor monocytes (less than 1 platelet/50 monocytes) cultured with [35S]methionine produced [35S] TSP barely detectable by immunoprecipitation with either monoclonal or polyclonal antibody to TSP. Platelet-poor monocytes that had not been so thoroughly depleted of platelets (6-12 platelets/50 monocytes) synthesized readily detectable amounts of [35S] TSP. Addition of increasing numbers of washed platelets to platelet-poor monocytes resulted in increasing synthesis of [35S]TSP. This monocyte-platelet interaction was specific for cell type; neither neutrophils nor red cells could substitute for platelets. The induction of synthesis was specific for TSP; monocyte synthesis of three other proteins was not induced upon the addition of platelets. Platelet lysate or thrombin-induced platelet releasate could not substitute for intact platelets. In fact, platelet lysate inhibited [35S]TSP synthesis by monocyte-platelet cultures. This inhibition was not due to endotoxin contamination, interference with immunoprecipitation, or dilution of the [35S]methionine pool. Platelets required contact with monocytes to exert their effect, as culturing the cell populations with a filter between them prevented increased [35S]TSP synthesis. Monocyte-platelet interactions may serve to specifically increase monocyte synthesis of the adhesive protein, TSP.

Blood Platelets↗
PubMed1985

Induction and enhancement by monocytes of antibody-induced modulation of a variety of human lymphoid cell surface antigens.

We have previously reported that the addition of monocytes results in enhanced modulation of the T65 antigen when normal or leukemic lymphoid cells were cultured in vitro with the T101 monoclonal antibody. In the present investigation, we extend these findings to demonstrate that monocyte-enhanced modulation is a phenomenon that occurs with a variety of T and B lymphoid antigens identified by murine monoclonal antibodies. Two patterns of monocyte-enhanced modulation were observed: (1) augmentation by monocytes of existing antigen modulation by the T101 and anti-Leu-4 antibodies, and (2) induction by monocytes of previously unrecognized modulation with the anti-Leu-2 and anti-Leu-9 antibodies. Enhancement of modulation by monocytes was also detected with antibodies to surface IgM and HLA-DR antigens. Antigen modulation on lymphoid cell lines appeared to be more variable than on fresh cells, with or without monocytes. Monocyte-enhanced antigen modulation was not demonstrated with two monoclonal antibodies against solid tumors. Monocyte-enhanced modulation was shown to be dependent upon the Fc portion of the antibody, but independent of proteolytic or oxidative compounds released by monocytes. These findings indicate that the results obtained during in vitro studies of antigen modulation may vary with the source of cells and the extent to which monocytic cells are present. In addition, these findings suggest an enhanced role for Fc receptor-bearing cells of monocytic origin in antigen modulation following in vivo administration of monoclonal antibodies.

Adult↗
PubMed1988

Defective interleukin-1 production in a familial monocyte disorder with a combined abnormality of mobility and phagocytosis-killing.

Monocytes in a familial monocyte disorder, a recently recognized primary immunodeficiency syndrome, with impaired phagocytic functions were studied for their ability to produce interleukin 1 (IL-1) as well as the surface property. Monocytes from two children (siblings) with the disorder possessed CD11b, CD13, CD14, CD33, Ia and LFA-1/Mac-1/p150,95 beta subunit antigens as determined by flow cytometry. Electron microscopic cytochemistry showed that the monocytes had surface glycoproteins reactive with four representative lectins. The IL-1 production by monocytes was assayed in the two patients and compared with that in six children with primary immunodeficiency syndromes and some monocyte abnormalities; three had congenital neutropenia, two had hyper-IgE syndrome, and one had defective monocyte chemotaxis. Monocyte culture supernatants were prepared with stimulation by lipopolysaccharide or silica, and their IL-1 activity was measured by the mouse thymocyte-proliferation assay. The patients' monocytes were defective in IL-1 production: the values were less than 1.0% of the control monocyte values (n = 12) and were in contrast with those of congenital neutropenia monocytes of 186.2% to 204.3%. These results demonstrate a familial monocyte disorder which is characteristic among the immunodeficiency syndromes with regard to the defective IL-1 production and the impaired phagocytic functions.

Adolescent↗
PubMed1987

Expression of HLA class II antigens and secretion of interleukin-1 by monocytes and macrophages from adults and neonates.

HLA class II antigen expression and IL-1 production by mononuclear phagocytes are important for antigen-stimulated T-cell activation. We examined these surface antigens and a monocyte marker antigen on fresh cord and adult blood monocytes, macrophages (M phi) derived from monocytes in vitro, human placental (fetal) M phi, from adult women. By FACS analysis, we found less DR on cord blood monocytes (80 +/- 7) than on adult monocytes (96 +/- 1) with greater heterogeneity in density of DR due to a weakly staining subpopulation of cord monocytes. There were markedly fewer DR and DQ positive placental M phi, 62 +/- 11% and 19 +/- 3%, compared to adult peritoneal M phi, 91 +/- 11% and 87 +/- 13%. DQ was more intense on peritoneal M phi than on any other cell type. Fresh cord monocytes secreted equal or greater amounts of interleukin-1 (IL-1) in response to lipopolysaccharide (LPS) or Group B streptococci than adult monocytes, although results with individual preparations varied. By Northern blot analysis, LPS-stimulated cord blood and adult monocytes contained similar amounts of IL-1 alpha, IL-1 beta and DR alpha mRNA. Each placental M phi preparation secreted IL-1 (200 +/- 85 U/ml to LPS). Peritoneal M phi preparations from women in the pre-luteal phase did not release detectable IL-1, whereas those from women in the post-luteal phase released as much as monocytes. Cultured monocytes failed to secrete IL-1 and expressed less DQ than fresh monocytes. Exposure to IFN gamma augmented IL-1 release by adult and cord cells and DQ expression on cord cells. These data indicate that class II antigen expression and IL-1 secretion by mononuclear phagocytes are only in part co-ordinately modulated. The differences between placental (fetal) M phi and adult peritoneal M phi may reflect both tissue-specific differences and generally diminished class II antigen expression on fetal and neonatal mononuclear phagocytes.

Adult↗
PubMed1985

Rapid killing of actinomycin D-treated tumor cells by human monocytes. II. Cytotoxicity is independent of secretion of reactive oxygen intermediates and is suppressed by protease inhibitors.

Pretreatment with Actinomycin D (ActD, 1 microgram/ml for 3 hr) rendered WEHI 164 tumor cells susceptible to killing by human monocytes in a 6-hr 51Cr release assay. The present study was designed to elucidate the role of reactive oxygen intermediates (ROI) and of proteolytic enzymes in this reactivity. ActD-treated WEHI 164 cells did not trigger any measurable release of O-2 or H2O2 from monocytes. Monocytes exposed to phorbol-12-myristate-13-acetate, which enhanced release of ROI, did not show augmented killing of ActD-treated tumor cells. Scavengers of oxygen metabolites (catalase, superoxide dismutase, gluthatione, and mannitol), which inhibited ROI-mediated PMA-induced monocyte cytotoxicity against erythrocytes, did not affect monocyte killing of ActD-treated WEHI 164 cells. Enzymatically generated ROI with xanthine/xanthine-oxidase glucose/glucose-oxidase did not show preferential killing of ActD-treated WEHI 164 cells. Two patients with chronic granulomatous disease had normal levels of monocyte cytotoxicity against ActD-treated tumor cells. To determine the possible role of proteolytic enzymes in mediating this reactivity, we studied various antiproteases. Organophosphorous agents (DFP and PMSF), chloromethyl-ketone derivatives of tosylamino acids (TLCK and TPCK), Actinomyces products (pepstatin and chymostatin), and the synthetic protease substrate TAME inhibited monocyte-mediated cytotoxicity against ActD-treated WEHI 164 cells. The macromolecular protease inhibitors alpha-1 antitrypsin, bovine pancreatic trypsin inhibitor (BPTI), soybean trypsin inhibitor, and the synthetic protease substrate ATEE had little effect on monocyte cytotoxicity. When monocytes were preincubated with drugs for 1 hr and washed, TLCK, TPCK, and PMSF inhibited cytolysis, whereas the less effective chymostatin and TAME and the inactive BPTI had no effect under these conditions. Inhibition by preincubation with TLCK, PMSF, and TPCK was completely reversed after 6 hr of culture. Supernatants of monocyte cultures had lytic activity against ActD-treated WEHI 164 but not against untreated cells. Antiproteases inhibited the lytic activity of monocyte supernatants. These results strongly suggest that ROI do not play a critical role in monocyte-mediated rapid killing of drug-treated tumor cells, and that proteolytic enzymes are involved in this reactivity.

Adolescent↗
PubMed1985

Monocytes in rheumatoid arthritis. Regulatory, effector, and phenotypic properties.

We reported that rheumatoid arthritis (RA) blood mononuclear cells (MNC) secreted less Ig and IgM rheumatoid factor (RF) than synovial cells. Since antibody elaboration is partly monocyte dependent, we compared regulatory, effector, and phenotypic properties of monocytes from 31 patients with RA with those of 21 normal subjects. RA IgG and IgM elaboration was less than normal. Monocyte, T or B cell numbers were comparable in RA and normal MNC and monocyte enriched/depleted preparations. RA and normal Ig production were monocyte dependent and this differed for IgG and IgM for RA and normals. IgM RF elaboration by stimulated RA MNC was also monocyte dependent and addition of normal monocytes/monocyte culture supernatants to RA monocyte depleted cultures and vice versa had inconsistent effects. RA MNC (Ficoll-Hypaque) phagocytosis was less than normal; killing (acridine orange fluorescent microscopy) was not. RA synovial monocyte phagocytosis - but not killing was also reduced. MNC from RA patients and normals contained similar numbers of monocytes; RA monocyte enriched populations (Percoll) showed less phagocytosis than normal; with similar killing. RA phagocytosis was reduced at 1,2,3,4 and 5 h and differed from normal at 3 and 5 h. Different sera - FCS, autologous, normal, RA - exhibited inconsistent effects on phagocytosis. RA and normal neutrophil phagocytosis and killing were comparable. Lastly, RA monocyte enriched preparations contained populations of OKM1, OKM3, OKM5, OKM6, Leu M1, Leu M2, Leu M3, and HLA-DR-positive cells (FACS analysis) comparable with normals. Regulatory and effector but not phenotypic properties of RA blood monocytes differed from normal and may contribute to inappropriate autoantibody production and chronic inflammation.

Arthritis, Rheumatoid↗
PubMed1982

Interactions between fresh human blood monocytes and tumor targets at the single cell level: binding and morphological characteristics.

Highly purified (97-99%), human peripheral blood monocytes, isolated by an EDTA-reversible adherence procedure, exhibit spontaneous killing in a rapid, 51Cr-release assay. Using the single cell conjugate/dextran assay, we have quantitatively determined select requirements for the adhesion of monocytes to neoplastic target cells. Monocytes expressed a broad binding capacity to a wide spectrum of nonadherent tumor cell lines, while binding at minimal levels to nontumor target cells. Binding of monocytes to K562 tumor cells is an extremely rapid event, reaching saturation levels within 5 min after cosedimentation. The binding of monocytes to K562 targets was reduced by low temperatures and pretreatment with metabolic inhibitors. Pretreatment of monocytes with cytoskeletal-disruptive drugs significantly reduced binding. Monocytes were shown to exhibit a specific, Mg2+-dependent, Ca2+-independent mechanism in their binding to K562 cells. Subsequent to binding, Ca2+ was required for monocyte-mediated target cell lysis to proceed. The binding of tumor cells by monocytes was studied morphologically using transmission (TEM) and scanning electron microscopic (SEM) techniques. It was observed that binding was achieved initially through complex, surface membrane interdigitations from apposing effector--target cells and progressed to stable conjugates, which were characterized by contact regions consisting of large expanses of closely apposed surface membranes. The application of the single cell conjugate/dextran assay to assess monocyte-binding requirements and the morphological characterization of the monocyte--target cell conjugation process may help in clarifying the mechanisms of monocyte-mediated tumor cell lysis.

Binding Sites↗
PubMed1995

Binding of FimD on Bordetella pertussis to very late antigen-5 on monocytes activates complement receptor type 3 via protein tyrosine kinases.

Nonopsonized Bordetella pertussis bind to human monocytes by means of the virulence factors filamentous hemagglutinin (FHA), pertactin, and the minor fimbrial subunit FimD. Receptors on monocytes that mediate binding of B. pertussis to these cells include complement receptor type 3 (CR3), which binds to FHA of B. pertussis, and very late antigen-5 (VLA-5), which binds to an, as yet, unknown ligand on these bacteria. In the present study, the possibility that FimD acts as a ligand for VLA-5 was investigated. Soluble fibronectin, which is the natural ligand for VLA-5, or mAbs against VLA-5 inhibited binding to monocytes of B. pertussis strains that express FimD but not of mutant strains that lack FimD. Beads that were coated with the fusion protein maltose-binding protein-FimD bound to adherent monocytes, and this binding was inhibited by soluble fibronectin or mAb against the alpha- or beta-chain of VLA-5, while soluble collagen or mAb against VLA-4, VLA-6, CR3, or HLA class II had no effect. Down-modulation of VLA-5 on the apical surface of monocytes by plating the cells onto surfaces precoated with anti-VLA-5 mAb also inhibited binding of beads coated with maltose-binding protein-FimD to monocytes, while precoating of the surfaces with mAb against VLA-6 or CR3 had no effect. These results indicate that VLA-5 on monocytes serves as a receptor for FimD on B. pertussis. Binding of C3bi-coated erythrocytes to monocytes, which is a measure of the binding activity of CR3, was enhanced when monocytes were adhered onto plates precoated with purified fimbriae of B. pertussis, while precoating with fimbriae lacking FimD had no effect. Precoating of the plates with FimD-containing fimbriae also enhanced binding of B. pertussis, which express FHA, but not of strains that lack FHA, to monocytes. The enhanced binding of C3bi-coated erythrocytes and B. pertussis to monocytes could be markedly inhibited by tyrphostin-47, a protein tyrosine kinase inhibitor. These results demonstrate that interaction of FimD of B. pertussis with VLA-5 on monocytes activates CR3, which requires protein tyrosine kinases and results in enhanced binding of B. pertussis to the latter receptor via FHA.

Bacterial Adhesion↗
PubMed1994

Histaminergic regulation of NK cells. Role of monocyte-derived reactive oxygen metabolites.

Monocytes, recovered by centrifugal elutriation, effectively inhibit functions of human NK cells in vitro. Histamine, acting via monocyte H2-type histamine receptors, abrogates the inhibitory signal. The aim of this study was to define the histamine-reversible mechanism by which monocytes inhibit NK cells with special reference to the respiratory burst activity of monocytes. Monocytes recovered from patients with chronic granulomatous disease did not suppress NK cell function, indicating the requirement of intact nicotinamide-adenine dinucleotide phosphate (NAPDH) oxidase activity of monocytes to inhibit NK cells. Furthermore, catalase, a scavenger of hydrogen peroxide (H2O2), was found to potently reverse the monocyte-induced inhibition of NK cell function; on the other hand, superoxide dismutase (a scavenger of superoxide anion), hydroxyl radical scavengers such as mannitol and deferoxamine, the hypochlorous acid scavenger taurin, or the nitric oxide synthetase inhibitor NG-monomethyl-L-arginine (L-NMMA) did not affect the monocyte-derived, suppressive signal. H2O2, at micromolar concentrations, reconstituted the inhibitory effects of monocytes on NK cell function. Histamine had no scavenger activity but effectively suppressed the generation of H2O2 in isolated monocytes. This effect of histamine was transduced by H2-type histamine receptors. We conclude that the histamine-reversible, inhibitory effect of elutriated monocytes on NK cells is dependent on the formation of reactive oxygen metabolites by monocytes and that H2O2 is a pivotal mediator of the suppressive signal.

Cytotoxicity Tests, Immunologic↗
PubMed1994

An endothelial cell adhesion protein for monocytes recognized by monoclonal antibody IG9. Expression in vivo in inflamed human vessels and atherosclerotic human and Watanabe rabbit vessels.

BACKGROUND: Monocyte adhesion to the vascular endothelium, an important component of an inflammatory response, is one of the earliest detected events in the pathogenesis of atherosclerosis. We have identified a monocyte adhesion molecule, recognized by monoclonal antibody (mAb) IG9, on the cell surface of human umbilical vein endothelial cells (HUVEC) treated with tumor necrosis factor-alpha (TNF-alpha), interleukin-1, or lipopolysaccharide. Endothelial cell expression in vitro and in vivo of the protein recognized by mAb IG9 (IG9 protein) was further characterized. EXPERIMENTAL DESIGN: The kinetics of cytokine-induced IG9 protein expression on HUVEC were evaluated by enzyme-linked immunosorbent assay. TNF-alpha-treated HUVEC surface proteins, labeled with [125I]Na, were solubilized in NP-40 detergent and immunoprecipitated with mAb IG9 to determine the molecular weight of the IG9 protein. The functional role of the IG9 protein in monocyte binding in vitro to cytokine-activated endothelial cells was established in adhesion assays utilizing U937 cells (human promyelomonocytic cell line) and human peripheral blood monocytes. Minimally oxidized or modified low density lipoproteins (MM-LDL) have previously been shown to induce monocyte adhesion to endothelial cells for up to 48 hours after exposure. In order to characterize the adhesion molecule(s) contributing to this increase in monocyte binding, MM-LDL-treated HUVEC and human aortic endothelial cells were assayed for monocyte adhesion molecule expression by enzyme-linked immunosorbent assay. In addition, mAb IG9-mediated alterations in MM-LDL-induced monocyte binding were studied in endothelial-monocyte adhesion assays. To assess IG9 protein expression in vivo, formalin-fixed, paraffin-embedded sections of inflamed human tissues obtained from lung and healing myocardial infarctions, in addition to sections of human atherosclerotic coronary arteries, were analyzed by immunohistochemistry. Tissue sections from atherosclerotic Watanabe heritable hyperlipidemic rabbit aortas were also included in these studies. RESULTS: The IG9 protein, undetected on untreated HUVEC, was expressed on their cell surface within 3 hours of treatment with TNF-alpha, peaked at 4 to 9 hours, and persisted for up to 48 hours as determined by enzyme-linked immunosorbent assay. A similar kinetic profile was elicited by interleukin-1 and lipopolysaccharide, whereas interferon-gamma (IFN-gamma) had minimal effect on IG9 expression. The IG9 protein has a molecular weight of 105,000 as determined by immunoprecipitation studies with TNF-alpha-treated HUVEC protein lysates. mAb IG9 significantly inhibited the binding of U937 cells and human peripheral blood monocytes to TNF-alpha-treated HUVEC and had no effect on peripheral blood lymphocyte or granulocyte adhesion. Treatment of human aortic endothelial cells or HUVEC with MM-LDL for 24 hours induced IG9 protein expression 3-fold above background with no concomitant increase in binding of antibodies to intercellular adhesion molecule-1 (ICAM-1), E-selectin, or vascular cell adhesion molecule-1 (VCAM-1), endothelial cell adhesion proteins involved in monocyte binding. mAb IG9 F(ab')2 inhibited MM-LDL-induced monocyte adhesion to HAEC by 23%. Immunohistochemical analysis demonstrated that the endothelial cell lining of vessels in human lung and heart with evidence of inflammation characterized by an extensive mononuclear cell infiltration exhibited reactivity with mAb IG9, whereas vessels with no evidence of inflammation in the same sections as well as in sections from normal lung and heart were nonreactive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Activation of human monocytes by the pineal hormone melatonin.

To determine the effects of the pineal hormone melatonin on human monocytes, human monocytes were activated by different concentrations of melatonin. Above the activation threshold of 5 x 10(-11) M, melatonin was able to induce the cytotoxicity of human monocytes, the secretion of IL-1, and the production of reactive oxygen intermediates. Melatonin and LPS seemed to have a synergistic effect on human monocyte activation. Indeed, below their respective monocyte activation threshold (5 x 10(-11) M and 0.625 ng/ml), melatonin (10(-12) M) in association with LPS (0.2 ng/ml) was able to induce cytotoxicity, IL-1 secretion, and reactive oxygen intermediates production. Melatonin alone at 10(-12) M or LPS alone at 0.2 ng/ml did not activate monocytes. Furthermore, melatonin was able to prime the monocytes for a subsequent activation by LPS. When monocytes were activated by LPS (0.25 ng/ml) at the time that they were plated and then activated by melatonin (10(-12) M) 8 h later, no IL-1 secretion and no cytotoxicity were detected. However, when the cells were first activated by melatonin (10(-12) M), and then 8 h later by LPS (0.25 ng/ml), IL-1 secretion and monocyte cytotoxicity were observed. Above its monocyte activation threshold, melatonin induces both cell-associated IL-1 alpha and IL-1 beta activities. Below this activation threshold, i.e., at 10(-12) M, melatonin does not induce the cell-associated IL-1 alpha and IL-1 beta activities, but does induce the mRNA for both IL-1 (alpha and beta). It seems that melatonin activates monocytes through protein kinase C. These data suggest that melatonin activates monocytes and induces their cytotoxic properties, along with the IL-1 secretion.

Blotting, Northern↗
PubMed1994

Rapid induction of arachidonic acid release by monocyte chemotactic protein-1 and related chemokines. Role of Ca2+ influx, synergism with platelet-activating factor and significance for chemotaxis.

Monocyte Chemotactic Protein-1 (MCP-1), a member of the Cys-Cys branch of the chemokine superfamily, induced a mepacrine- and manoalide-sensitive increase in the release of [3H]arachidonic acid from prelabeled human monocytes and monocytic THP-1 leukemic cells. The effect was rapid (<30 s), reached maximum at optimal chemotactic concentrations, and was completely blocked by pretreatment of monocytes with Bordetella pertussis toxin. A specific antiserum and heat inactivation blocked the induction of arachidonic release by MCP-1. No [3H]arachidonic acid release was observed in the absence of Ca2+ influx (5 mM EGTA or 5 mM Ni2+) or in monocytes loaded with a Ca(2+)-buffering agent. However, using ionophore-permeabilized monocytes and controlled intracellular Ca2+ concentration it was possible to dissociate MCP-1-induced Ca2+ influx from [3H]arachidonic acid release. Thus, the MCP-1-induced increase in [Ca2+]i is necessary but not sufficient for arachidonic acid accumulation. Phospholipase A2 inhibitors (mepacrine, p-bromophenacyl bromide, and manoalide) blocked monocyte polarization and chemotaxis induced by MCP-1. The related Cys-Cys chemokines RANTES and LD78/MIP1 alpha also induced a rapid release of [3H]arachidonic acid, and their chemotactic activity was blocked by phospholipase A2 inhibitors. Brief (5 min) pretreatment of monocytes with platelet-activating factor amplified MCP-1-induced arachidonic acid release and, at MCP-1 suboptimal concentrations, synergized in inducing monocyte migration. Since MCP-1 and platelet-activating factor are induced concomitantly by inflammatory cytokines in monocytes and endothelial cells, we speculate that the observed synergism may have in vivo relevance. The results presented here show that the Cys-Cys chemokines MCP-1, LD78/MIP1 alpha, and RANTES cause rapid release of arachidonic acid in monocytes and that this may be important in inducing monocyte chemotaxis.

Arachidonic Acid↗
PubMed1993

Comparative accessory cell function of human peripheral blood dendritic cells and monocytes.

The capacity of human peripheral blood (PB) dendritic cells (DC) and monocytes to facilitate T cell activation and the interaction molecules employed were compared. We have shown that precursors of DC constitute 2 to 3% of circulating PBMC, and can be isolated as CD33+CD14dim cells, whereas monocytes are CD33+CD14bright. Freshly obtained DC expressed similar densities of HLA-DR and the accessory molecules LFA-3, ICAM-1, and B7 as monocytes; after a 36-h incubation the expression of HLA-DR, ICAM-1, and B7 increased on both APC. Accessory cell function was examined in PB T cell cultures stimulated by suboptimal concentrations of immobilized mAb to CD3, and by stimulation of an allospecific T cell line. Freshly isolated monocytes and DC were comparable accessory cells in these assays, but their accessory function was increased by in vitro preincubation, although cultured DC and monocytes were comparably active. In contrast, DC were much more effective stimulators of freshly isolated allogeneic T cells than monocytes. DC were much more effective stimulators of freshly isolated allogeneic PB CD4+ naive and memory T cells than monocytes, whereas DC and monocytes were comparable accessory cells for memory and naive T cells stimulated with immobilized anti-CD3. The accessory molecules ICAM-1, LFA-3, and B7 were used comparably by DC and monocytes for accessory function in the presence of immobilized anti-CD3 and in the MLR, and none was unique for either APC population. These accessory molecules costimulated T cells in an additive fashion. Although immature blood DC and monocytes expressed minimal B7 and did not utilize it as an accessory molecule, B7 played an important role in the increased accessory function of differentiated APC. The results indicate that PB DC and monocytes function most efficiently after differentiation into mature cells that express increased amounts of MHC and other accessory molecules. Because DC and monocytes exhibit comparable accessory function in anti-CD3 T cell stimulation, differences in the expression of MHC molecules and/or their bound peptides are likely to explain the markedly enhanced capacity of DC to stimulate allogeneic PB T cells.

Adult↗
PubMed1996

IL-10 production is enhanced in human T cells by IL-12 and IL-6 and in monocytes by tumor necrosis factor-alpha.

IL-10, an immunoregulatory cytokine produced by T cells and monocytes, inhibits the expression of inflammatory and hemopoietic cytokines as well as its own expression. To evaluate the regulation of IL-10 production by T cells and monocytes, we measured IL-10 levels by ELISA in supernatants of PHA-stimulated PBMC following depletion of either T cells or monocytes. IL-10 production was significantly down-regulated in both T cell- and monocyte-depleted PBMC compared with undepleted PBMC, and IL-10 production could be restored by the addition of monocyte-conditioned medium (supernatant of PHA-stimulated, T cell-depleted PBMC), suggesting that IL-10 production by T cells is regulated by a monokine(s) produced by activated monocytes. To further clarify the monokine(s) responsible for IL-10 induction, we stimulated monocyte-depleted PBMC, purified CD4+, and CD8+ T cells with PHA and measured IL-10 production by ELISA and semiquantitative reverse transcriptase-PCR following monokine(s) addition. Addition of IL-6 and IL-12 enhanced IL-10 production in monocyte-depleted PBMC in a dose-dependent and additive manner. Furthermore, anti-IL-6 and anti-IL-12 Abs neutralized the IL-10-inductive effect of monocyte-conditioned medium. Similarly, IL-12 and IL-6 induced IL-10 production by purified CD4+ and CD8+ T cells. With respect to regulation of IL-10 produced by monocytes, TNF-alpha was found to induce IL-10 production by resting as well as by LPS-stimulated purified monocytes/macrophages. Taken together, these findings suggest that IL-10 production by human T cells and monocytes is differentially regulated. IL-12 and/or IL-6 can induce the expression of IL-10 by PHA-stimulated T cells, whereas TNF-alpha induces IL-10 production by monocytes. Since IL-10 inhibits the production of IL-6, IL-12, and TNF-alpha, these results may indicate a potential mechanism of negative feedback regulation of the immune response.

Adjuvants, Immunologic↗
PubMed1996

HIV-1-Tat protein promotes chemotaxis and invasive behavior by monocytes.

Monocytes are susceptible to HIV infection and to activation by a regulatory gene product of the HIV genome, HIV-Tat. Recently, we have demonstrated that treatment with HIV-Tat up-regulates monocyte adhesion to the endothelium and increases metalloproteinase production. in the present study, we have examined the ability of the HIV-Tat protein to alter the migratory and invasive behavior of monocytes. Monocytes pretreated for 24 h with 10 ng/ml HIV-Tat exhibited enhanced migratory behavior compared with untreated monocytes in chemotaxis assays, both in the absence of a chemoattractant as well as in response to FMLP. in addition, HIV-Tat itself induced the migration of both untreated and HIV-Tat pretreated monocytes. Checkerboard analysis showed that monocytes migrated in response to an HIV-Tat concentration gradient, thus confirming the chemotactic characteristics of the HIV-Tat protein. Pretreatment of monocytes with 10 ng/ml HIV-Tat for 24 h also increased their ability to invade reconstituted extracellular membrane (Matrigel)-coated filters by 5-fold in the absence of chemoattractant. The presence of FMLP or HIV-Tat further enhanced invasion by both untreated and HIV-Tat-pretreated monocytes by more than 10-fold. Monocyte invasion was partially inhibited by the inclusion of anti-beta integrin Ab or tissue inhibitor of metalloproteinase (TIMP). Thus, for the first time, we present evidence that HIV-Tat can enhance the chemotactic and invasive behaviors of monocytes and propose an active role for HIV-Tat in the recruitment of monocytes into extravascular tissues, a process which may contribute to the destruction of tissues and cellular architecture often seen in patients with acquired immunodeficiency syndrome.

Chemotaxis, Leukocyte↗
PubMed1997

Monocyte chemotactic protein-1 concentration in peritoneal fluid of women with endometriosis and its modulation of expression in mesothelial cells.

OBJECTIVE: To investigate monocyte chemotactic protein-1 concentrations in the peritoneal fluid (PF) of women with or without endometriosis, then assess peritoneal mesothelial cells as a potential source of monocyte chemotactic protein-1. DESIGN: Prospective study. SETTING: University medical center. PATIENT(S): Women with (n = 60) or without (n = 18) endometriosis. INTERVENTION(S): First monocyte chemotactic protein-1 levels in PF were measured, then mesothelial cells in culture were treated with cytokines. MAIN OUTCOME MEASURE(S): In PF and culture supernatants, monocyte chemotactic protein-1 was measured by ELISA. In vitro monocyte chemotactic protein-1 messenger RNA expression was evaluated by Northern analysis. RESULT(S): The median concentration of monocyte chemotactic protein-1 in PF of control women was 137 pg/mL (conversion factor to SI unit, 0.115; range, 12 to 418 pg/mL); that of women with moderate endometriosis was 205 pg/mL (range 65 to 6,000 pg/mL); and that of those with severe endometriosis was 1,165 pg/mL (0 to 2,602 pg/mL). Within the moderate to severe endometriosis group, monocyte chemotactic protein-1 levels were higher in women with untreated endometriosis (354 pg/mL range 0 to 6,000 pg/mL) than in women receiving GnRH agonist (128 pg/mL, range 0 to 216 pg/mL). In the control group, monocyte chemotactic protein-1 levels were higher in the proliferative phase than in the secretory phase. Mesothelial cells produced constitutively monocyte chemotactic protein-1; moreover, both interleukin-1 alpha and tumor necrosis factor-alpha induced higher levels of monocyte chemotactic protein-1. CONCLUSION(S): Levels of monocyte chemotactic protein-1 in PF were higher during the proliferative phase than secretory phase of control women and increased in moderate to severe endometriosis. The regulated expression of monocyte chemotactic protein-1 may recruit macrophages into PF and contribute to the pathogenesis of endometriosis.

Antineoplastic Agents, Hormonal↗