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A monocyte disorder in siblings with chronic candidiasis. A combined abnormality of monocyte mobility and phagocytosis-killing ability.

Immunologic studies were performed on siblings (a 9-year-old boy and an 11-year-old girl) with chronic candidiasis since infancy and showed defective monocyte functions. In vivo migration and in vitro mobility of the monocytes were impaired. In addition, they had defective phagocytosis-killing ability against Candida albicans. There was no factor(s) to inhibit the monocyte functions in the patients' serum, and their mononuclear cells (75% to 80% lymphocytes) did not secrete such an inhibitory factor(s) in vitro. The serum IgG, IgA, IgM, and C3 levels were normal. Delayed hypersensitivity responses to five antigens, including Candida antigen, were absent in the two patients. In vitro T-lymphocyte functions, such as Candida antigen- or mitogen-induced blastogenesis and lymphokine (leukocyte migration inhibitory factor and leukocyte-derived chemotactic factor) production, were normal. The clinical features of our patients were similar to those with chronic mucocutaneous candidiasis (CMC); however, their primary immunologic defect was, unlike that of CMC, in monocytes, but not in T lymphocytes. These results demonstrated a monocyte disorder with defective mobility and phagocytosis-killing ability that contributed to chronic candidiasis.

Blood Bactericidal Activity↗

Monocyte chemotactic protein-1 stimulates the killing of leishmania major by human monocytes, acts synergistically with IFN-gamma and is antagonized by IL-4.

We recently demonstrated that monocyte chemotactic protein-1 (MCP-1) is strongly expressed in lesions of patients with self-healing localized cutaneous leishmaniasis (LCL) whereas it is scarce in those of chronic diffuse cutaneous leishmaniasis (DCL). This finding indicated that MCP-1 may contribute to the healing process. In the present study, we analyzed the capacity of MCP-1 to trigger leishmanicidal activities. The results show that MCP-1 directly stimulates the elimination of intracellular Leishmania parasites by human monocytes, a potential that correlates with the induction of reactive oxygen intermediates. Release of NO was not detected. To understand the cross-talk between the chemokine and T cell-associated cytokines, we studied the influence of the Th1 cytokine IFN-gamma and the Th2 cytokine IL-4 on MCP-1-mediated activation of human monocytes. The data demonstrate that IFN-gamma and MCP-1 synergistically activate monocytes to clear intracellular parasites, whereas IL-4 abrogates the effect of MCP-1. Furthermore, IL-4 inhibits MCP-1 expression by infected monocytes, a finding that may explain the lack of MCP-1 in chronic lesions. The data suggest a novel model for macrophage activation in cutaneous leishmaniasis. In lesions of LCL, the synergistic action of MCP-1 and IFN-gamma may stimulate the killing of parasites by macrophages and promote healing, whereas the presence of IL-4 in DCL lesions may favor the suppression of MCP-1 and, together with the lack of IFN-gamma, the progression of disease.

Animals↗

Chemiluminescence of human bloodstream monocytes and neutrophils: an unusual oxidant(s) generated by monocytes during the respiratory burst.

Maximal rates of O2- and H2O2 production by human bloodstream monocytes activated during the respiratory burst by phorbol ester were only about 10% of those of neutrophils. Furthermore, monocytes possess only about 5% of the myeloperoxidase activity of neutrophils and so can only produce low levels of HOCl and related compounds. These combined reductions in O2- generating ability and lower myeloperoxidase levels result in low levels of luminol chemiluminescence stimulated during the respiratory burst of monocytes. However, although monocytes generate much lower levels of O2- and H2O2 than neutrophils, these cells produce comparable rates of PMA-stimulated lucigenin chemiluminescence. Hence, this assay does not accurately reflect the production of either of these two oxidants by activated phagocytes, and further lucigenin must react with some other oxidant(s) via a process which leads to photon emission. This oxidant(s) is not O2-, H2O2, .OH, 1O2 or NO, but is derived from O2- generated during the respiratory burst and is generated in greater quantities by activated monocytes compared with neutrophils. Thus, lucigenin chemiluminescence is an indirect measure of superoxide release.

Acridines↗

Constitutive production of PAI-II and increased surface expression of GM1 ganglioside by peripheral blood monocytes from patients with AIDS: evidence of monocyte activation in vivo.

To characterize the activation state of monocytes during human immunodeficiency virus (HIV) infection, peripheral blood monocytes (PBMs) from patients with acquired immunodeficiency syndrome (n = 10) and from healthy controls (n = 10) were cultured for 4 days. Monocyte culture supernatant (MCS) was collected daily, and levels of urokinase (UK) inhibitor PAI-II, a product of activated monocytes, released into MCS were determined (fibrin plate assay). To examine the activation state of PBMs independently, expression of GM1 ganglioside on PBMs from patients with AIDS (n = 9), patients with AIDS-related complex (ARC) (n = 8), HIV+ asymptomatic patients (n = 6), and HIV- healthy controls (n = 11) was determined (flow cytometry; living cells in suspension). Data are expressed as percent inhibition of UK, or as percent total cells. Patients' MCS collected on days 1-4 of culture contained similar levels of PAI-II because it inhibited UK in similar fashion (70-90%). In contrast, MCS from healthy controls, collected after 2 days, had decreased ability to inhibit UK (15-50%) and thus contained lower levels of PAI-II. Monocyte activation, measured by increased expression of GM1 ganglioside on PBM surfaces, directly correlated with the progression of HIV infection into the development of AIDS, since the order of magnitude of GM1 ganglioside expression on PBMs was AIDS greater than ARC greater than HIV+ asymptomatic = healthy controls. Our data indicate that PBMs from patients with AIDS are constitutively activated and suggest that activation directly correlates with disease progression.

Acquired Immunodeficiency Syndrome↗

Granulocyte-monocyte progenitor cells from human peripheral blood: modulation of growth in vitro by T lymphocytes and monocytes.

Cell fractionation techniques have been used for the purification and characterization of hematopoietic cells present in peripheral blood and bone marrow. Following fractionation, the distribution of hematopoietic cells is frequently determined by the granulocyte-monocyte colony-forming unit (CFU-gm) assay. In this study, we questioned whether the purification process itself altered the sensitivity of the CFU-gm assay through changes in the accessory cell populations. Experiments showed that following T cell depletion, the cloning efficiency of CFU-gm was suboptimal, since the addition of autologous T lymphocytes was stimulatory, even when the concentration of conditioned medium was optimal. In contrast, growth of CFU-gm was inhibited by monocytes, both in the presence and absence of T cells. Sensitivity to monocyte-derived inhibition occurred at significantly lower monocyte concentrations when T cells were present. Thus, stem cell purification techniques which deplete T lymphocytes or enrich monocytes have an adverse effect on the cloning efficiency of peripheral blood CFU-gm. This study presents culture techniques capable of circumventing these problems.

Bone Marrow Cells↗

Co-culture of human monocytes and thyrocytes in bicameral chamber: monocyte-derived IL-1alpha impairs the thyroid epithelial barrier.

Pro-inflammatory cytokines are important mediators in tissue responses to a wide range of endogenous (e.g. autoantigens) and exogenous (e.g. infections, wounds, biomaterials) stimuli. The complex interactions taking place between different cell types in such processes are difficult to examine in vivo. Here we studied the effect of human monocytes on thyroid epithelial cells co-cultured in bicameral chambers. Freshly isolated monocytes (1x10(6)/ml) added to the basal compartment reduced the transepithelial resistance (from 300-600 to <100 Omega.cm(2)) and caused a disruption of the tight junctions in apically grown thyrocyte monolayers after co-culture for 24 h. The barrier function was further attenuated by monocytes exposed to lipopolysaccharide (10 microg/ml) or polystyrene microspheres (size: 3 microm; 1x10(7)/ml). Loss of transepithelial resistance was accompanied by release of interleukin 1alpha (maximally 550 pg/ml) from the monocytes. Conversely, the resistance remained high when co-cultures were simultaneously incubated with neutralizing anti-human interleukin 1alpha antibodies. The results show that the integrity of cultured thyroid epithelium is impaired by monocytes without requirement of direct cell-to-cell contact. This action, mediated by interleukin-1alpha, suggests a mechanism by which hidden (lumenal) autoantigens might be exposed to interstitial antigen-presenting cells in autoimmune thyroid disease. In perspective, the model provides a tool in which humoral and cell-cell dependent processes generated by bioactive agents and particulate materials, for instance, during the healing and repair of tissue around biomaterials and hybrid implants, can be selectively examined.

Antigen-Presenting Cells↗

Gene expression of monocyte chemoattractant protein-1 in human monocytes is regulated by cell density through protein tyrosine kinase and protein kinase C.

The present study investigated the signal transduction pathways leading to the gene expression for monocyte chemoattractant protein-1 (MCP-1) in human monocytes. By Northern blot analysis, MCP-1 mRNA was undetectable in freshly isolated monocytes, but was induced and reached a maximal level at 4 h during culture. The level of accumulated mRNA altered with cell density of the monocytes and was highest at a density of 1 x 10(6) cells/ml. Nuclear run-on assay demonstrated that this cell density-dependent expression of MCP-1 mRNA was regulated at the transcriptional level, and protein tyrosine kinase (PTK) inhibitors, genistein and herbimycin A, completely abrogated this gene transcription. Immunoblot analysis for phosphotyrosine in whole cell lysates demonstrated gradual increases in tyrosine phosphorylation of 55-, 60-, and 70-kDa proteins during culture. Cell density regulated tyrosine phosphorylation of 70-kDa protein in parallel with alterations in MCP-1 mRNA expression. The protein kinase C (PKC) inhibitor H-7 also abrogated the gene transcription and suppressed tyrosine phosphorylation of 70-kDa protein, whereas HA1004, a structural analogue of H-7, did not. These results suggest that MCP-1 gene expression in cultured monocytes is regulated by the cell density at the transcriptional level and that the signaling pathways leading to the gene transcription are mediated through PTK and PKC. It is also suggested that PKC activity plays a critical role in tyrosine phosphorylation of 70-kDa protein, which may mediate signals regulating the cell density-dependent expression of the MCP-1 gene.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

Influence of surgical stress on monocytes and complications of infection in patients with esophageal cancer--monocyte HLA-DR antigen expression and respiratory burst capacity.

We investigated how surgical stress affects the phenotypic and functional properties of peripheral blood monocytes, especially the expression of human leukocyte antigen DR (HLA-DR), Mac-1 antigen, and respiratory burst capacity. Then, we analyzed the relation between these monocyte parameters and septic complications following esophagectomy. Increased H2O2 production (605.3 +/- 95.3 fluorescence intensity (FI) vs 441.8 +/- 55.5 FI) in the preoperative period and decreased HLA-DR expression (20.5 +/- 5.5% vs 39.6 +/- 11.1%) on monocytes on the 1st postoperative day (POD) were found in esophagectomy patients (n = 14) compared with gastrectomy patients (n = 29). Furthermore, the level of increased H2O2 production and decreased HLA-DR expression continued on the 8th and 14th POD in the esophagectomy group with septic complications compared with the esophagectomy group without septic complications. These results suggested that patients with septic complications following esophagectomy had alterations of monocyte phenotype and function. This monocyte analysis may contribute to our understanding of the complicated mechanism involved in surgical stress and the development of postoperative septic complications.

Aged↗

Terminal Ph1-positive monocytic crisis in chronic myeloid leukemia providing evidence for the promyelocytic origin of monocytes.

A case of Ph1-positive chronic granulocytic leukemia in described in which a terminal monocytic crisis developed. The case still was Ph1-positive at the time of the monocyte crisis. Bone marrow smears contained promyelocytes and early granulocytes, but most of the cells belonged to the monocyte series as cytochemistry disclosed. No blast cells could be detected. Cytochemically, transitions between promyelocytes and promonocytes could be demonstrated. From these findings and those from the literature it is concluded that the monocytes of the terminal crisis in our case belonged to the leukemic cell strain and that these monocytes developed from non-specific promyelocytes like granulocytes. Our observation does not provide evidence for the existence of a separate monoblast which would implicate disparity of granulocytopoiesis and monocytopoiesis already at the level of undifferentiated blast cells. This, in turn, would be equal to a re-introduction of a modified polyphyletic theory of white blood cell formation.

Adult↗

Liposome-encapsulated muramyl tripeptide up-regulates monocyte chemotactic and activating factor gene expression in human monocytes at the transcriptional and post-transcriptional levels.

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a novel immune modulator that is now under investigation against metastatic melanoma and osteosarcoma. We have already reported that L-MTP-PE induced monocyte-mediated tumoricidal activity and up-regulation of the tumor necrosis factor and interleukin-1 (IL-1) in vivo and in vitro. We now demonstrate that L-MTP-PE also induces monocyte chemotactic and activating factor (MCAF) mRNA expression at both the transcriptional and post-transcriptional levels. Monocyte chemotactic activity was also present in the supernatants of L-MTP-PE-stimulated cells. In monocytes, the increased expression of MCAF was induced rapidly (by 2 h) but was short-lived. By 4 h, MCAF mRNA had decreased to background level. We found no change in MCAF mRNA levels in lymphocytes exposed to L-MTP-PE. We therefore conclude that L-MTP-PE selectively up-regulates MCAF expression in monocytes and that MCAF may play a role in the tumoricidal and immune-stimulating activity of L-MTP-PE.

Acetylmuramyl-Alanyl-Isoglutamine↗

Expression of fructosyllysine receptors on human monocytes and monocyte-like cell lines.

Short-term exposure of human serum albumin to glucose in vitro results in the formation of fructosyllysine residues. Using short-term glucose-modified albumin the interactions with human monocytes and with the human monocyte-like cells U937, MonoMac 6, HL60, and THP1 were studied. Short-term glycated albumin was specifically bound by monocytes, U937 and MonoMac 6 cells, but not by HL60 and THP1 cells. This specific binding of short-term glycated albumin was inhibited by fructosyllysine, but not by hexitollysine. Short-term glycated albumin did not compete for binding of albumin, modified by advanced glycation end products. Scatchard analysis of the binding data indicated that there are 10,000 binding sites per cell in monocytes or U937 cells and 2000 sites per cell on MonoMac 6 cells with affinity constants of 9 x 10(6) M-1. Specific binding of short-term glycated albumin to human monocytes was observed in 29% of the 101 human subjects investigated. Ligand-receptor cross-linking and ligand blotting experiments revealed two binding proteins of 100 to 110 and 190 kDa in SDS-PAGE after membrane protein solubilization of U937 and MonoMac 6 cells. The binding of short-term glycated albumin to MonoMac 6 cells induced the production of the cytokines IL-1 and TNF.

Binding Sites↗

Toll-like receptor, MHC II, B7 and cytokine expression by porcine monocytes and monocyte-derived dendritic cells in response to microbial pathogen-associated molecular patterns.

To evaluate effects of treatment with pathogen-associated molecular patterns (PAMPs) on toll-like receptor (TLR), MHC II, B7 and cytokine expression, pig monocytes and monocyte-derived DCs (moDCs) were treated with LPS, CpG, lipoteichoic acid (LTA), poly IC or peptidoglycan (Pep). Monocytes and moDCs treated with LPS, CpG, LTA, poly IC or Pep altered expression of at least one TLR (4, 5 and 9) and up-regulated MHC II and/or B7. The mRNA for IL-4 was not detected after any treatment. Treatment with LPS or LTA tended to up-regulate mRNA for TLR 4, Th-1 (IFN-gamma and IL-12p35) and Th-2 cytokines (IL-10 and IL-13). Poly IC or CpG tended to up-regulate TLR 9 and Th-1 cytokines. Porcine monocytes and moDCs like those of humans and mice responded to microbial PAMPs by altering TLR expression, up-regulating MHC II and B7 and altering cytokine expression toward Th-1 and/or Th-2, which may steer immune response. Hence, porcine moDCs and monocytes are likely able to discriminate between microorganisms using TLRs which determine cytokine expression and immune response bias.

Animals↗

Replication of bovine respiratory syncytial virus in bovine and ovine peripheral blood lymphocytes and monocytes and monocytic cell lines.

The present study compared the replication of bovine respiratory syncytial virus (BRSV) in bovine and ovine peripheral blood mononuclear cells, ovine and bovine monocytic cell lines and ovine alveolar macrophages. Low titres of virus were detected in ovine and bovine lymphocytes and monocytes 24-96 h post-exposure to the virus but there was no apparent replication of the virus in ovine alveolar macrophages during the culture period. The virus replicated to higher but statistically insignificant titres in ovine and bovine peripheral blood monocytes than in lymphocytes, with lymphocytes yielding peak titres significantly earlier. The secondary cell lines obtained from ovine liver and bone marrow also supported the replication of BRSV to high titres. The titres of BRSV in ovine and bovine lymphocytes and monocytes were significantly lower than in secondary cell lines. The addition of human recombinant tumour necrosis factor alpha after exposure to the virus or pre-incubation of ovine or bovine monocytic cells with either human recombinant interleukin 2 or phorbol myristate acetate before exposure to BRSV, did not significantly affect virus titre. Pre-incubation of cells with indomethacin or actinomycin significantly lowered virus titre (p < 0.05).

Animals↗

Monocytes in inflammatory bowel disease: monocyte and serum lysosomal enzyme activity.

1. The activity of a specific lysosomal marker enzyme N'-acetyl-beta-D-glucosaminidase has been determined fluorimetrically in the monocytes and in the serum of patients with Crohn's disease and ulcerative colitis and compared with results obtained from healthy and disease control subjects. 2. Enzyme activities were measured in a monocyte-enriched suspension from a Ficoll-Triosil gradient and in an adherent monocyte preparation. 3. The results indicate that enzyme activity is greater in both monocytes and sera of patients with Crohn's disease and ulcerative colitis than in those from control subjects (P less than 0.01). 4. Enzyme activity within monocytes correlated with disease activity (P less than 0.05). 5. Lysosomal enzymes may contribute to the pathogenesis of the mucosal inflammation in inflammatory bowel disease.

Acetylglucosaminidase↗

Infection of human endothelial cells with Staphylococcus aureus induces the production of monocyte chemotactic protein-1 (MCP-1) and monocyte chemotaxis.

Bacterial infection coincides with migration of leucocytes from the circulation into the bacterium-infected tissue. Recently, we have shown that endothelial cells, upon binding and ingestion of Staphylococcus aureus, exhibit proinflammatory properties including procoagulant activity and increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression on the cell surface, resulting in hyperadhesiveness, mainly for monocytes. The enhanced extravasation of monocytes to bacterium-infected sites is facilitated by the local production of chemotactic factors. From another study we concluded that the locally produced chemokine MCP-1 is important in the recruitment of monocytes to the peritoneal cavity in a model of bacterial peritonitis. In the present study we investigated whether cultured human endothelial cells after infection with bacteria produce and release MCP-1, which in turn stimulates monocyte chemotaxis. We observed that endothelial cells released significant amounts of MCP-1 within 48 h after ingestion of S. aureus. This was dependent on the number and the virulence of the bacteria used to infect the endothelial cells. The kinetics as well as the amount of MCP-1 released by S. aureus-infected endothelial cells differed markedly from that released by endothelial cells upon stimulation with IL-1beta. Supernatant from S. aureus-infected or IL-1beta-stimulated cells promoted monocyte chemotaxis which was almost entirely abrogated in the presence of neutralizing anti-MCP-1 antibody, indicating that most of the chemotactic activity was due to the release of MCP-1 into the supernatant. Our findings support the notion that endothelial cells can actively initiate and sustain an inflammatory response after an encounter with pathogenic microorganisms, without the intervention of macrophage-derived proinflammatory cytokines.

Cells, Cultured↗

Molecular mechanism of monocyte predominant infiltration in chronic inflammation: mediation by a novel monocyte chemotactic factor, S19 ribosomal protein dimer.

A novel monocyte chemotactic factor, a cross-linked homodimer of S19 ribosomal protein (RP S19) was initially isolated from a rheumatoid arthritis synovial lesion. The RP S19 dimer causes the monocyte specific chemotaxis in vitro and the monocyte predominant infiltration in vivo, via its agonistic and antagonistic effects on the C5a receptors of monocytes and polymorphonuclear leukocytes, respectively. The agonistic effect is attributed to the similarity of regional structures between RP S19 and C5a, the complement C5-derived leukocyte chemotactic factor, although overall homology of the amino acid sequence between these molecules is only 4%. The antagonistic effect depends upon the C-terminal portion of RP S19. The RP S19 dimer is produced and released by apoptotic cells, and this dimer recruits monocytes from the circulation to the apoptotic lesion. The infiltrated monocytes/macrophages engulf the apoptotic cells, translocate to regional lymph nodes via lymphatics and present the antigenic information of the apoptotic cells to the T cell repertoire. In this manner, the apoptotic cell clearance system connects to the acquired immune system. The innate and acquired immune mechanisms, mediated by the RP S19 dimer, participate in the pathology of inveterate chronic inflammation such as rheumatoid arthritis.

Amino Acid Sequence↗

Phenotypic and functional outcome of human monocytes or monocyte-derived dendritic cells in a dermal equivalent.

The dermis harbors a true dendritic cell population that could elicit primary allogeneic T cell responses in vitro and contact hypersensitivity reactions in vivo. The origin of dermal dendritic cells remains poorly understood, however. In this study, we analyzed the fate of monocytes or monocyte-derived dendritic cells in a dermal equivalent. Freshly isolated monocytes or monocytes cultured for 6 d with either GM-CSF/IL-4 or GM-CSF/IL-4/TGF-beta 1 (TGF-DC) were seeded in a collagen solution with normal human fibroblasts. The lattices were cultured for 7--14 d in the presence, or absence, of the exogenous cytokines, before phenotypic and functional studies were performed. Supply of exogenous cytokines allows the appearance of typical CD1a(+)/CD14(-)/CD68(low) dendritic cells with significant allostimulatory property, regardless of the cell type incorporated into the lattices. In cytokine-free conditions, monocytes and GM-CSF/IL-4-derived dendritic cells give rise to a CD1a(-)/CD14(+)/CD68(high) monocyte/macrophage population with no allostimulatory property. When incorporated into the lattices in the absence of exogenous cytokines the TGF-DC express few CD68 and FXIIIa. Interestingly, these cells do not all convert into the CD14(+)/CD1a(-) population. Indeed, a small HLA-DR(+)/CD1a(+)/CD14(-) subset was consistently found, which represents about one-third of the HLA-DR(+) cells. Moreover, TGF-DC recovered from the lattices after culture without cytokines do display a significant allostimulatory function. Thus, in the absence of exogenous cytokines, only Langerhans-cell-like dendritic cells can retain the typical dendritic cell features when inserted in a dermal environment. Taken together, these results may provide evidence supporting an epidermal origin of dermal dendritic cells.

Antigens, CD1↗

Endothelial intracellular Ca2+ release following monocyte adhesion is required for the transendothelial migration of monocytes.

Although molecular changes accompanying leukocyte extravasation have been investigated intensively, the particular events following leukocyte adhesion and leading to the actual transendothelial migration process remain largely unknown. To characterize intraendothelial signals elicited by leukocyte adhesion and functionally required for their transmigration, we recorded endothelial free cytosolic intracellular Ca(2+)levels ([Ca(2+)]i) during the course of leukocyte adhesion. We show that monocyte and granulocyte adhesion induced Ca(2+)transients in either untreated or TNF-alpha-stimulated microvascular endothelial cells (HMEC-1). The functional significance of these [Ca(2+)]i rises was demonstrated by treating filter-grown endothelial monolayers with BAPTA/AM. This in traendothelial Ca(2+)chelation left monocyte adhesion basically unaffected, but caused a significant and dose-dependent reduction of the transendothelial migration of monocytes. Granulocyte diapedesis, on the other hand, was hardly modified. Thapsigargin-treatment of endothelial cells almost completely inhibited the transmigration of monocytes suggesting that the necessary Ca(2+)transients depended on a release from intracellular Ca(2+)stores. Our results thus show that the transmigration of monocytes through endothelial monolayers of microvascular origin is favoured by an increase of the intraendothelial [Ca(2+)]i induced by leukocyte adhesion to the endothelial cells.

Calcium↗