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.

SourceResearch connectionFrom yearThrough year

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

At least 685 records · Page 38Linked to original sources

PubMed1986

Regulation of the synthesis of the third component of complement and factor B in cord blood monocytes by lipopolysaccharide.

We compared the regulation of C3 and factor B synthesis in cord blood and adult monocytes by using techniques for identification and quantification of newly synthesized proteins, lipopolysaccharide (LPS) from several Gram-negative organisms, and precursors of LPS. Synthesis of C3 and factor B in cord blood monocytes was unaffected by lipid A (the active moiety of LPS extracted by the Westphal procedure). In contrast, adult monocytes increased C3 synthesis by 11.5-fold and factor B synthesis by 3.1-fold in response to LPS. This difference in cord blood monocyte response to LPS was specific in that other LPS-induced monocyte functions (superoxide production and phagocytosis) were stimulated comparably in both cord blood and adult monocytes by LPS. To characterize further this regulatory difference, the roles of LPS precursors, arachidonic acid metabolites, and of factor(s) released by adult monocytes were examined. Precursors of the lipid portion of LPS (lipid X and lipid Y), LPS isolated by trichloroacetic acid extraction, and endotoxin-associated protein (EAP) increased C3 and factor B synthesis in cord blood monocytes. Inhibitors of the lipoxygenase pathway (dexamethasone, ETYA) but not of the cyclooxygenase pathway (indomethacin) abrogated the response of adult monocytes to lipid A and EAP and of cord blood monocytes to EAP. Finally, co-incubation of adult monocytes and cord blood monocytes in LPS-containing medium resulted in enhancement of C3 and factor B synthesis in cord blood monocytes. These data suggest that the difference in LPS response between cord blood and adult monocytes may result from differences in lipid processing or protein recognition of LPS, differences in the production of lipoxygenase pathway products, and/or one or more regulatory factors. The availability of human mononuclear phagocytes which exhibit distinct differences in biosynthetic responsiveness to LPS should permit investigation of the molecular mechanism(s) by which LPS affects C3 and factor B gene expression.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed1986

In vitro infection of human monocytes with human T lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV).

We explored the possibility that normal human monocytes can be infected with the retrovirus human T lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). The T4 antigen, believed to be the receptor for HTLV-III/LAV binding to CD4 cells, is found on monocytes at low levels. Anti-T4A, which recognizes an epitope on the T4 molecule, inhibits viral binding to monocytes, and virus inhibits anti-T4A binding, although inhibition in both cases is not total. Virus particles were detected in HTLV-III/LAV-pulsed monocytes by electron microscopy as early as 10 min and for up to 3 days after inoculation, although budding virus was not observed. Monocytes were exposed to virus, were washed, and were cultured. Monocyte cultures were monitored by conventional assays for virus replication: immunofluorescence detection of cytoplasmic virus, supernatant reverse transcriptase activity, and supernatant virus antigen. These assays were either negative or at the lower limits of positivity. However, the amount of infectious virus was shown to increase over time in monocyte cultures by harvesting monocytes or their culture supernatants and titrating them into assay cultures containing stimulated T cells. Virus recovery from monocytes and virus recovery from T cells differed both quantitatively and qualitatively. Recovery from T cells and T cell supernatants peaked at 3 to 6 days and declined thereafter. Recovery from monocytes and monocyte supernatants increased over time in culture and never attained the levels of T cell cultures. Taken together, these studies indicate that HTLV-III/LAV binds to monocytes via the T4 molecule and enters the cells. Infectious virus is retained and increases with time in infected monocyte cultures. Both viral binding and infection are at low levels compared with levels in T cells. Unlike the usual infection of T cells characterized by high level virus replication with cell depletion, the infection appears to be persistent in monocytes.

Antibodies, Monoclonal↗

PubMed1987

In vitro studies of human monocyte migration across endothelium in response to leukotriene B4 and f-Met-Leu-Phe.

Relatively little is known about monocyte emigration from the vasculature or about the factors that regulate this process. In this study, a human in vitro model of a blood vessel wall was used for examination of monocyte transendothelial migration. Umbilical vein endothelial cells were grown to confluency on amnion connective tissue, and human monocytes were stimulated to cross the monolayer in response to the chemoattractants leukotriene B4 or f-Met-Leu-Phe. The pattern and time course of monocyte migration were similar for the two chemotactic factors. In both cases, approximately 40-50% of the adherent monocytes extended single or multiple pseudopods into the apical endothelial surface. This indenting behavior was also observed in the absence of chemotactic factors. It was not affected by the medium (M199 or Gey's) or method of monocyte isolation. Neutrophils also displayed this behavior, but only about half as many neutrophils as monocytes indented the endothelial surface. The integrity of the endothelium remained intact as the monocytes traversed the monolayer. When the monocytes reached the basal surface of the endothelium, they frequently wedged themselves between the basal surface of the endothelium and its basal lamina. The monocytes then invaded the basal lamina and accumulated in the connective tissue. In response to both f-Met-Leu-Phe and leukotriene B4, monocyte migration across the endothelium began as early as 10 minutes. The average rate of accumulation in the connective tissue peaked at 30 minutes; and by 60 minutes, 25-35% of the monocytes had traversed the monolayer. Approximately two to three times as many monocytes traversed the endothelium under conditions of chemotaxis as under conditions of chemokinesis or random migration. These studies provide the basis for understanding the process of monocyte migration out of the bloodstream and lay the foundation for the study of their differentiation into macrophages in the connective tissue.

Amnion↗

PubMed1986

Interferon-gamma-activated human monocytes inhibit the intracellular multiplication of Legionella pneumophila.

We have examined the interaction between interferon-gamma (IFN-gamma)-activated human monocytes and Legionella pneumophila, the agent of Legionnaires' disease. Human monocytes activated with human recombinant IFN-gamma inhibit the intracellular multiplication of L. pneumophila. The degree of inhibition is proportional to the concentration of IFN-gamma, and maximal inhibition consistently occurs with greater than or equal to 2 micrograms/ml. Monoclonal anti-IFN-gamma antibody completely neutralizes the capacity of IFN-gamma to activate monocytes. Monocytes infected 24 hr after explantation maximally inhibit L. pneumophila multiplication if treated with IFN-gamma before infection or up to 2 hr after infection; treatment 6 hr or more after infection results in submaximal inhibition. Monocytes infected 48 hr after explantation inhibit L. pneumophila multiplication maximally if treated with IFN-gamma up to 12 hr before infection, but submaximally if treated at the time of infection. Once activated, monocytes inhibit L. pneumophila multiplication in the absence of IFN-gamma in the culture. Strikingly, monocytes maximally inhibit L. pneumophila multiplication after treatment with IFN-gamma for as briefly as 1 hr before infection. In the absence of anti-L. pneumophila antibody, neither IFN-gamma-activated monocytes nor nonactivated monocytes kill L. pneumophila. In the presence of specific antibody and complement, IFN-gamma-activated monocytes kill a proportion (0.5 log) of an inoculum but not more than nonactivated monocytes. L. pneumophila forms a specialized phagosome in IFN-gamma-activated monocytes that does not differ ultrastructurally from the L. pneumophila phagosome in nonactivated monocytes. These results demonstrate that IFN-gamma can activate human monocytes to exert a potent antimicrobial effect against a highly virulent intracellular bacterial pathogen. These findings extend previous observations on interactions between activated mononuclear phagocytes and L. pneumophila, and additionally support the hypothesis that cell-mediated immunity plays a major role in host defense against L. pneumophila.

Cells, Cultured↗

PubMed1987

Recombinant interferons or interleukin-2 increase cytotoxicity by human monocytes and NK cells.

Human peripheral blood monocytes and NK cell enriched lymphocytes were purified by counterflow centrifugal elutriation. The cell populations were characterized by surface marker analysis using monoclonal antibodies. A variety of molecules were found to be capable of activating monocytes and NK cells to enhanced tumoricidal activity. Tumoricidal activity was evaluated using a colorimetric microassay. Numbers of tumor cell targets surviving exposure to monocytes or NK cells were calculated by computer analysis of colorimetric data derived by target cell-dependent dye reduction. The results indicated that monocyte effector cells were cytotoxic to the NK sensitive K562 cell line and to the monocyte sensitive TU5 line. Depletion of NK contaminants from the monocyte population by complement mediated cytolysis did not affect the capacity of the monocytes to kill either target. Monocyte mediated cytotoxicity was enhanced by treatment of the monocytes with recombinant IFN-alpha, IFN-beta, or IFN-tau; each in a dose-dependent manner. Simultaneous treatment of monocytes with IFN-alpha and IFN-tau resulted in additive but not synergistic effects. NK cell cytotoxicity was enhanced by treatment with IL-2 or IFN-tau. Enhancement of monocyte and NK cell cytotoxicity by IFN or IL-2 was dependent upon the time in culture of the effector cells, the duration of the effector phase, and the effector to target cell ratio. IFN or IL-2 treatment alone did not reduce target cell viability. The results suggest that monocytes as well as NK cells are capable of providing a natural defence against neoplasia, that monocytes can kill NK targets and NK cells can kill monocyte targets, and that these cytotoxic activities are enhanced by IFN or IL-2.

Cell Line↗

PubMed1988

Monocyte retention and migration in pulmonary inflammation. Requirement for neutrophils.

The acute inflammatory process is characterized by an orderly progression of events; an initial phase of early neutrophil accumulation and a later phase of mononuclear cell (including monocyte) accumulation. The mechanisms which control the transition from one phase to the other are largely unknown. We present a rabbit model of C5 fragment (C5f)-induced lung inflammation in which purified radiolabeled peripheral blood neutrophils and monocytes were used as probes to monitor the retention and emigration of these leukocytes into well localized areas of inflammation. Neutrophil preparations (greater than 95% pure) were isolated by discontinuous plasma-Percoll density gradients, and monocyte preparations (greater than 91% pure) were isolated by counterflow cell elutriation, labeled with 111Indium-tropolonate, and intravenously infused into separate recipient animals. The monocytes circulated with a half-life of approximately 30 hours. The retention of labeled monocytes or neutrophils within the lung was monitored scintigraphically. C5f-induced monocyte lung retention was delayed 2 to 4 hours compared with neutrophil lung retention. Radiolabeled neutrophils were selectively retained in the area of C5f-induced inflammation (right cranial lung lobe, RCL) as early as 20 minutes after the induction of the inflammatory response, reached a maximum by 2 hours, and were not retained by 48 hours after C5f instillation. The signal inducing C5f-induced monocyte lung retention was shown to be transient. Monocytes were selectively retained in the RCL if the area of inflammation was induced 2 to 4 hours but not 15 minutes or 16 hours before their infusion. The time course of C5f-induced monocyte migration into the alveolar space determined by lavage analysis was delayed 2 to 3 hours compared with neutrophil migration. Neutrophils selectively migrated into the RCL 1 to 2 hours after the induction of the inflammatory response, reached a maximum by 4 hours, and had disappeared by 48 hours. Radiolabeled monocytes selectively migrated into the RCL 3 to 4 hours after the induction of the inflammatory response, reached a maximum by 4 hours, and remained present through 48 hours. The total number of labeled and unlabeled mononuclear cells present in the C5f-treated RCL lavage at 48 hours was significantly increased above controls. The signal for this monocyte migration (as for lung retention) was shown to be transient in that radiolabeled monocytes did not migrate when infused 16 hours after the induction of the inflammatory response. C5f did not induce monocyte lung retention nor monocyte migration into the alveolar space of animals rendered neutropenic.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1982

Activation and immunoregulation of antigen-specific human b lymphocyte responses: multifaceted role of the monocyte.

The multifaceted role of the monocyte in the induction and modulation of antigen-specific antibody responses by human B cells was delineated. Monocytes were absolutely required for the induction of specific antibody responses to both TT and KLH in an antigen-induced in vitro assay. Monocytes were also required for the PWM induction of specific antibody in immunized subjects. Pulsing monocytes with specific antigen or with PWM consistently stimulated proliferation of T cells in absence of added antigen and could also stimulate specific antibody synthesis although less consistently. Stimulation of specific antibody responses with antigen required fewer numbers of monocytes than did stimulation of specific antibody responses with PWM. Polyclonal antibody synthesis induced by PWM was also dependent on monocytes. However, polyclonal antibody synthesis induced by supraoptimal concentrations of antigen was usually optimal in the absence of monocytes and was actually suppressed when increased numbers of monocytes were added to monocyte-depleted cultures. Monocyte supernatants could not replace the absolute requirements for monocytes in the induction of specific antibody synthesis. However, monocyte supernatants could profoundly modulate the antigen-specific as well as the polyclonal Ig response of lymphocytes to either antigen or PWM stimulation in a manner closely resembling monocytes themselves. Thus, we demonstrated that monocytes and their products play a critical role in the activation and immunoregulation of antigen-specific antibody responses of human B cells.

Antibody Formation↗

PubMed1995

Monocytes control gamma/delta T-cell responses by a secreted product.

Gamma-irradiated ex vivo bovine monocytes induce proliferation of gamma/delta T cells in the autologous mixed lymphocyte reaction (AMLR), whereas when not irradiated they prevent this response. In contrast, non-irradiated autologous monocytes have no effect on bovine alpha/beta T-cell proliferation in the allogenic MLR suggesting that the regulation is specific for gamma/delta T-cell responses. Here, we showed that the inhibition was not mediated by inducing cell death and that the ability of ex vivo monocytes to prevent proliferation of gamma/delta T cells was not generalized in that gamma/delta T cells still responded to mitogenic stimulation. Inhibition of the AMLR by non-irradiated monocytes could not be overcome by addition of interleukin-2 to the cultures or by costimulation with antibodies to WC1, a gamma/delta T-cell-specific cell-surface differentiation antigen shown elsewhere by us to be involved in activation of gamma/delta T cells. Furthermore, we showed that monocytes inhibited gamma/delta T-cell responses via a soluble product since inhibition occurred even when monocytes and gamma/delta T cells were separated by membranes of transwells or when supernatants from monocyte cultures were added to AMLR cultures. Maximal secretion of the inhibitory product by the monocytes occurred during the first 6 hr of in vitro culture at 37 degrees, rapidly decreased thereafter, and did not occur when monocytes were incubated at 4 degrees. The inhibition was not attributable to nitric oxide, reactive oxygen intermediates, prostaglandin E2 or transforming growth factor-beta (TGF-beta) but the ability of monocyte supernatants to mediate inhibition was sensitive to heating at 65 degrees. Lipopolysaccharide and granulocyte-macrophage colony-stimulating factor activation of monocytes temporarily abrogated their ability to inhibit proliferation. In contrast, heat-shocking had no effect on their ability to inhibit. We hypothesize that non-irradiated monocytes produce the inhibitory material in vivo in order to regulate gamma/delta T-cell responses to self-derived monocyte membrane components, but that when monocytes are altered by infection, transformation, irradiation, or cytokine activation, production of the inhibitor is temporarily suspended allowing stimulation of gamma/delta T cells to occur.

Animals↗

PubMed1997

Lipoprotein lipase enhances human monocyte adhesion to aortic endothelial cells.

Lipoprotein lipase (LPL)-mediated lipolysis of very low density lipoprotein (VLDL) has been demonstrated to increase U937 monocyte adhesion to endothelial cells. In the present study, we evaluated the ability of LPL to enhance human monocyte adhesion to bovine aortic endothelial cells (BAEC) in the absence of exogenous lipoproteins. Exposure of BAEC to 1 microgram/ml LPL at 37 degrees C resulted in a significant increase in monocyte adhesion over control values. Addition of VLDL in the culture media further enhanced the LPL effect. A significant increase in monocyte adhesion was also observed when BAEC were incubated with LPL at 4 degrees C. Heparin or heparinase treatment of BAEC totally abolished the LPL stimulatory effect on monocyte adhesion. In addition, incubation of monocytes with heparinase suppressed the ability of LPL to stimulate monocyte adhesion to endothelial cells. These treatments also markedly decreased LPL binding to the monocyte and endothelial cell surfaces. In contrast to native LPL, heat inactivated or phenylmethylsulfonyl fluoride (PMSF)-treated LPL did not increase monocyte adhesion to BAEC. Finally, incubation of LPL in the presence of the 5D2 antibody resulted in a total suppression of the LPL-induced monocyte adhesion to BAEC. Taken together, these data demonstrate that LPL activity plays an important role in LPL-induced monocyte adhesion and that LPL binding to heparan sulfate proteoglycans expressed on both monocytes and endothelial cells surfaces is required for the enhanced monocyte adhesion. These results suggest a new mechanism by which LPL may promote the development of atherosclerosis, that of facilitating monocyte adhesion to the endothelium.

Animals↗

PubMed1996

Fc gamma receptor I (CD64)-negative human monocytes are potent accessory cells in viral antigen-induced T cell activation and exhibit high IFN-alpha-producing capacity.

Blood monocytes represent a heterogeneous cell population with respect to phenotype and function. We have previously described that a minor subset of Fc gamma receptor I-negative (CD64-) monocytes, comprising < 10% of all monocytes, exhibits a significantly higher accessory capacity in allogeneic or purified protein derivative (PPD) of tuberculin-induced T cell activation than the majority of CD64-expressing (CD64+) monocytes. CD64- monocytes were also found to represent the major source of Newcastle disease virus (NDV)-induced interferon (IFN)-alpha within human monocytes. In the present study we demonstrate that CD64- monocytes are also the main producers of IFN-alpha in response to Herpes simplex virus type 1 (HSV-1) or influenza (type A) antigens. The virus-induced IFN-alpha release by monocytes, but mainly that by CD64- monocytes, can be further increased by co-culture with autologous T cells, which alone do not produce significant amounts of IFN-alpha in response to virus. In addition, CD64- and CD64+ monocytes also differ in their accessory capacity in virus-induced T cell responses. CD64- monocytes exposed to influenza antigens induced higher IFN-gamma release and proliferation by the responding autologous T cells than virus-exposed CD64+ monocytes. In virus-stimulated monocyte/T cell co-cultures, CD64- monocytes also induced larger size cell clusters than CD64+ monocytes, indicating direct cell-to-cell interaction with a higher number of T cells, which represent the main component of these clusters.

Antigen-Presenting Cells↗

PubMed1990

The in vitro development of cytotoxicity in response to granulocyte/macrophage-colony-stimulating factor or interferon gamma in the peripheral blood monocytes of patients with solid tumors: modulation by arachidonic acid metabolic inhibitors.

The capacity of granulocyte/macrophage-colony-stimulating factor (GM-CSF) and interferon gamma (IFN gamma) to elicit monocyte cytotoxicity in vitro in the peripheral blood monocytes of patients with solid tumors was investigated. The cytotoxicity elicited by IFN gamma was significantly reduced in cancer patient monocytes compared to normal monocytes. The cytotoxicity elicited by GM-CSF, however, was comparable between cancer patient monocytes and normal monocytes, but was lower than that induced by IFN gamma. Indomethacin, a cyclooxygenase inhibitor, significantly augmented IFN gamma-elicited cytotoxicity in cancer patient monocytes, but not in normal monocytes. In contrast, indomethacin augmented GM-CSF-elicited cytotoxicity in both cancer patient monocytes and normal monocytes. Nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, was found to suppress cytotoxicity in response to IFN gamma and GM-CSF in both cancer patient monocytes and normal monocytes. The addition of leukotrienes to NDGA-treated cultures restored the development of cytotoxicity. Thus there are differences in the in vitro response of cancer patient monocytes and normal monocytes to distinct biological activators. Furthermore, these responses can be manipulated by agents that modulate arachidonic acid metabolism.

Adult↗

PubMed2026

Monocytes Defined by Platelet Interactions and Oxidative Stress Signaling Underlie HIV-Associated Atherosclerosis.

BACKGROUND: Monocytes contribute to atherosclerosis by migrating into inflamed endothelium and differentiating into lipid-laden macrophages. In people living with HIV, chronic inflammation increases atherosclerosis risk, yet the role of specific monocyte subsets remains unclear. We investigated how distinct monocyte populations contribute to vascular pathology in early HIV-associated atherosclerosis. METHODS: We profiled 123 965 circulating monocytes using single-cell RNA sequencing and integrated plasma microparticle proteomics in 32 individuals stratified by HIV and atherosclerosis status. Supervised learning identified cluster- and disease-specific signatures, validated by platelet-monocyte cocultures, reverse transcription-quantitative polymerase chain reaction, bulk RNA sequencing, flow cytometry, and ELISA. RESULTS: Seven monocyte clusters were identified, including a subset characterized by platelet-monocyte complexes. Bulk RNA sequencing of platelet-monocyte cocultures revealed platelet-driven upregulation of genes involved in inflammation, lipid metabolism, oxidative stress, and endothelial adhesion. Platelet-monocyte complex-derived macrophages secreted higher levels of TGF-β (transforming growth factor-β) and IL-10 (interleukin-10), displayed decreased CD14 and increased CD80/CD86 while retaining CD36, and promoted endothelial-to-mesenchymal transition (decreased expression of CDH5 and PECAM1; increased expression of S100A4 and markers of vascular inflammation (ICAM1), VCAM), and IL-6 (interleukin-6), and CCL2 (C-C motif chemokine ligand 2) secretion). Additionally, CD14+ monocytes from HIV+ atherosclerosis-negative and HIV+ atherosclerosis-positive groups showed enhanced ROS-NRF2 (reactive oxygen species-nuclear factor erythroid 2-related factor 2) pathway activities, supported by increased basal and H2O2-induced p90RSK phosphorylation, indicating oxidative stress priming. CONCLUSIONS: Two monocyte clusters contribute independently to vascular immune dysregulation in people living with HIV. Platelet-monocyte complex-derived macrophages promote endothelial dysfunction while adopting a profibrotic cytokine profile. CD14+ monocytes show heightened oxidative signaling and stress responses, consistent with vascular activation. Together, these mechanisms may accelerate atherosclerosis development in HIV, even in the absence of traditional cardiovascular risk factors.

Humans↗

PubMed2000

Soluble vascular cell adhesion molecule 1 mediation of monocyte chemotaxis in rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is characterized by infiltration of leukocytes, including monocyte/ macrophages, into synovial tissue (ST), but factors mediating the ingress of these cells are poorly understood. Vascular cell adhesion molecule 1 (VCAM-1) plays an important role in adhesion of leukocytes to the vasculature. This study was undertaken to test the hypothesis that soluble VCAM-1 (sVCAM-1) might mediate chemotaxis of monocytes in RA. METHODS: Chemotaxis assays were performed using a modified Boyden chamber to determine the effects of sVCAM-1 on and the role of very late activation antigen 4 (VLA-4) in peripheral blood (PB) monocyte migration. Synovial fluids (SF) were immunodepleted of sVCAM-1 to identify a role for sVCAM-1 in RA. Immunohistochemistry and flow cytometry analyses were performed to show the expression of VLA-4 in ST, SF, and PB. Tyrosine phosphorylation was studied by Western blot analysis on PB monocyte lysates in the presence of signaling inhibitors. RESULTS: Soluble VCAM-1 induced monocyte migration in the nM range, in a concentration-dependent manner. Anti-VLA-4 significantly inhibited sVCAM-1-induced monocyte migration, suggesting that sVCAM-1 acts in part via a VLA-4-dependent mechanism. In RA SF, incubation with anti-VCAM-1 resulted in a reduction in the ability to induce monocyte migration (mean 28%). VLA-4 immunolocalized to RA ST, SF, or PB, monocytes, macrophages, and lymphocytes. Soluble VCAM-1 stimulated tyrosine phosphorylation in monocytes, and pertussis toxin, chelerythrine chloride, and staurosporine significantly reduced sVCAM-1-mediated monocyte chemotaxis, suggesting that signaling pathways via G proteins and protein kinase C are required for sVCAM-1-mediated monocyte migration. CONCLUSION: These results demonstrate a novel function for sVCAM-1 as a monocyte chemotactic agent in RA and suggest a new potential target for modulating monocyte ingress into inflamed RA ST.

Arthritis, Rheumatoid↗

PubMedDate not supplied

Activation of human monocytes by interleukin 2: role of T lymphocytes.

The effect of interleukin 2 (IL2) on the capability of human monocytes to secrete reactive oxygen species triggered via Fc-gamma receptor (Fc-gamma R) function had been investigated by measurement of chemiluminescence (CL). IL 2 did not activate highly purified (hp) monocytes to respond to Fc-gamma R mediated phagocytic stimulation with an enhanced respiratory burst activity unless low numbers of T cells had been co-cultured with hp monocytes. Supernatants from IL 2 treated PBMC contained interferon-gamma (IFN-gamma) and monocyte activating factor (MAF) activity. The secretion of both cytokine activities was strongly enhanced by cooperative function of monocytes. The correlation of IL 2 induced secretion of IFN-gamma and MAF activity was striking, however, monoclonal antibody (mAb) anti-human IFN-gamma failed to abrogate IL 2 stimulated and lymphocyte dependent monocyte activation. Although IL 2 had no direct monocyte activating effect, pretreatment of hp monocytes with IL 2 led to monocyte priming: subsequent co-culture with autologous control T cells enhanced the monocyte Fc-gamma R mediated CL response. The priming of monocytes by IL 2 was dependent on the interaction of IL 2 with the monocytic IL 2 receptor as shown by inhibition experiments with anti IL 2 R monoclonal antibody. Thus the IL 2 driven monocyte/T-cell interaction leads to an increased Fc-gamma R mediated monocytic respiratory burst activity and to the secretion of a soluble MAF activity, but there were no detectable amounts of IFN-gamma.

Antibodies, Monoclonal↗

PubMed1980

The requirement for monocytes in spontaneous cytotoxicity by lymphocytes from healthy donors and melanoma patients.

Lymphocytes from 12 healthy donors were depleted of monocytes by velocity sedimentation at unit gravity (average monocyte contamination 0.2%) and tested for spontaneous cytotoxicity (SC) against tumor target cells in 23 h microcytotoxicity assays. Sixty percent of all lymphocytes were recovered in this monocyte-depleted lymphocyte fraction (LF). In contrast, with the corresponding unfractionated lymphocytes (UL) the LF cells were not spontaneously cytotoxic on T24 bladder carcinoma, NKI-1, NKI-7, NKI-8, NKI-10 melanoma, and MC-1 mammary carcinoma cell line cells and target cells derived from two short-term melanona cultures (Me 215 and Me 223). SC of the LF could be restored by reconstitution with autologous monocytes, which were obtained > 80% pure in the same velocity sedimentation procedure. Addition of 4-8% monocytes was sufficient to restore the SC of the LF to the level achieved with the corresponding UL, whereas maximal induction of SC was observed after addition of 8-16% monocytes. Higher numbers of monocytes had suboptimal effects. SC of the LF could also be restored by monocyte culture supernatants. The spontaneous cytotoxic effector cells were characterized as non-E rosette-forming, membrane sIg-negative Fc-receptor-bearing lymphocytes, a proportion of which probably also bear C3-receptors. Since the LF was not spontaneously cytotoxic, in spite of the presence of Fc-receptor bearing lymphocytes, it is concluded that monocyte help, mediated via soluble factors, is required. Evidence is presented that the lack of SC by the LF might be attributable to the failure of these cells to make appropriate contact with the target cells. LF/target cell contact followed by target cell kill occurred after addition of monocytes. Effector/target cell contacts, artificially established by agglutinins, did not result in target cell kill. Thus the effector/target cell contacts observed in the presence of monocytes suggest recognition of particular membraner determinants involved in SC. An identical requirement for monocytes was observed with LF cells from 5 stage 1 and 5 stage 11 melanoma patients tested for SC against both melanoma and non-melanoma target cells. This indicates that either the cytotoxicity against melanoma cells with lymphocytes from melanoma patients is of the same nature as the SC of lymphocytes from healthy donors, or that specific melanoma-associated cellular cytotoxicioty also requires monocyte help.

Adult↗

PubMed1998

Reduced CD4 and HLA-DR expression in neonatal monocytes.

Three-color flow cytometry was used to assess the immunophenotypic characteristics of normal cord blood monocytes after labeling with a variety of antibodies against myeloid/monocyte-specific markers. Monocytes both in cord blood and in peripheral blood from normal adults were defined in a backgating procedure as cells with the light-scattering characteristics of monocytes that also expressed CD14. The percentage of monocytes, defined in this fashion, that also displayed CD4 receptors was significantly lower in cord blood (mean +/- SD = 29.3 +/- 13.9%) than in peripheral blood from normal adult controls (mean +/- SD = 68.9 +/- 13%) (P < 0.005). Similarly, HLA-DR expression was found on only 86 +/- 6.6% of monocytes in cord blood but on 99 +/- 1% of monocytes in adults (P < 0.005). The percentage of monocytes displaying CD16 receptors in cord blood did not show any significant difference in comparison with adult monocytes. When coexpression of CD14, CD16, and CD4 was assessed, cord blood showed a predominant population of monocytes bearing the phenotype CD14+/CD16-/CD4-. Similarly, approximately 10% of CD14+ monocytes in cord blood expressed neither CD4 nor HLA-DR. Cytochemically, monocytes from cord blood revealed intense granular staining for PAS and marginal or absent staining for nonspecific esterase (NSE). These results raise the possibility that reduced expression of CD4 and HLA-DR receptors on cord blood monocytes may contribute to their impaired immune response. Additionally, the high percentage of CD14+/CD16-/CD4- cells in cord blood suggests that these cells may represent a phenotypically immature population of monocytes. Likewise, the unusual cytochemical staining patterns suggest that these cells are biochemically immature as well.

Adult↗

PubMed1995

Monocyte adherence to the subendothelial basement membrane increases interleukin-8 gene expression and antigen release.

The emigration of peripheral blood monocytes into the interstitium allows for contact with a variety of surfaces which may provide signals important for monocyte function in both normal and inflammatory states. In the present study, we examined the effect of adherence to an endothelial cell-derived basement membrane and to collagen I, the major collagen of the interstitium, on monocyte release and gene expression of the potent chemotactic cytokine Interleukin-8 (IL-8). We further evaluated neutrophil chemotactic activity of the conditioned media containing antigenic IL-8 from monocytes adherent to these same surfaces. Elutriation-purified monocytes were adhered for 1 hour to plastic tissue culture wells either uncoated (PL) or coated with bovine serum albumin (BSA), collagen type I (C-I), or endothelial cell-derived basement membrane (BM). Following removal of nonadherent cells, monocytes were further incubated in a serum-free media for 18 hours in the presence or absence of lipopolysaccharide (IPS). Following 18 hrs of incubation there were significantly less monocytes remaining adherent to BM when compared to other surfaces tested. In the absence of LPS, adherent monocytes released significant amounts of IL-8 that was not surface specific. In the presence of LPS, monocytes adherent to BM released significantly more IL-8, when corrected for adherent cell number, than monocytes adherent to PL, BSA, or C-I. Conditioned media from adherent monocytes expressed IL-8 dependent neutrophil chemotactic activity that was not influenced by the surfaces tested. Northern blot analysis indicated greater induction for IL-8 mRNA by monocytes adhered to BM after 18 hrs in the presence of LPS. These results suggest that monocyte adherence to the subendothelial basement membrane provides a priming signal for the induction and secretion of the chemotactic cytokine IL-8 in response to inflammatory stimuli.

Antigens↗

PubMed1986

Lipopolysaccharide exposure during purification of human monocytes by adherence increases their recovery and cytolytic activity.

Exposure of monocytes to lipopolysaccharide (LPS) during, but not after, adherence purification increased their cytolytic activity in short-term 51Cr-release assays against K562 target cells. In the absence of LPS only a minority of monocytes could be recovered by adherence. With 1 ng/ml to 10 micrograms/ml LPS present during the 1-hr adherence procedure, however, monocytes spread more extensively on serum-coated plastic and glass surfaces and virtually all of the monocytes in a mononuclear leukocyte preparation were recovered in the adherent fraction. While increasing the recovery of monocytes threefold, LPS exposure during adherence also increased monocyte purity as assessed by peroxidase staining, morphology, and indirect immunofluorescence with monoclonal Mo2. The proportion of Leu-11-positive NK cells in the adherent fraction did not change. Depletion of NK cells by treatment with anti-Leu-11b and complement eliminated cytolytic activity from the nonadherent, but not from the adherent, fraction isolated with LPS. Thus, addition of LPS during adherence produced a monocyte preparation with enhanced cytolytic activity not attributable to NK contaminants. To test whether LPS caused production of lymphokines that activate monocytes, we tested supernatants of unseparated mononuclear leukocytes for the capacity to stimulate purified monocytes for cytolysis. Such supernatants stimulated monocytes more effectively than LPS alone. We conclude that LPS stimulates monocytes for cytolysis most effectively during adherence purification because LPS allows the recovery of weakly adherent monocytes with high cytolytic capacity; also, LPS may stimulate production of lymphokines that further augment monocyte cytolytic activity.

Cell Adhesion↗