CD147 overexpression on synoviocytes in rheumatoid arthritis enhances matrix metalloproteinase production and invasiveness of synoviocytes

Macrophage-like synoviocytes and fibroblast-like synoviocytes (FLS) are known as the most active cells of rheumatoid arthritis (RA) and are close to the articular cartilage in a position enabling them to invade the cartilage. Macrophage-like synoviocytes and FLS expression of matrix metalloproteinases (MMPs) and their interaction has aroused great interest. The present article studied the expression of CD147, also called extracellular matrix metalloproteinase inducer, on monocytes/macrophages and FLS from RA patients and its potential role in enhancing MMPs and the invasiveness of synoviocytes. Expression of CD147 on FLS derived from RA patients and from osteoarthritis patients, and expression of CD147 on monocytes/macrophages from rheumatic synovial fluid and healthy peripheral blood were analyzed by flow cytometry. The levels of CD147, MMP-2 and MMP-9 mRNA in FLS were detected by RT-PCR. The role of CD147 in MMP production and the cells' invasiveness in vitro were studied by the co-culture of FLS with the human THP-1 cell line or monocytes/macrophages, by gel zymography and by invasion assay. The results showed that the expression of CD147 was higher on RA FLS than on osteoarthritis FLS and was higher on monocytes/macrophages from rheumatic synovial fluid than on monocytes/macrophages from healthy peripheral blood. RT-PCR showed that the expressions of CD147, MMP-2 and MMP-9 mRNA was higher in RA FLS than in osteoarthritis FLS. A significantly elevated secretion and activation of MMP-2 and MMP-9 were observed in RA FLS co-cultured with differentiated THP-1 cells or RA synovial monocytes/macrophages, compared with those co-cultured with undifferentiated THP-1 cells or healthy control peripheral blood monocytes. Invasion assays showed an increased number of invading cells in the co-cultured RA FLS with differentiated THP-1 cells or RA synovial monocytes/macrophages. CD147 antagonistic peptide inhibited the MMP production and the invasive potential. Our studies demonstrated that the CD147 overexpression on monocytes/macrophages and FLS in RA patients may be responsible for the enhanced MMP secretion and activation and for the invasiveness of synoviocytes. These findings suggest that CD147 may be one of the important factors in progressive joint destruction of RA and that CD147 may be a potential therapeutic target in RA treatment.     

Morphologic, quantitative and cytoenzymologic studies of synoviocytic and monocytic cells in synovial fluid

The findings are presented of a morphologic, quantitative, cytochemical and cytoenzymologic study of the mononucleated nonlymphoid cells in knee synovial fluids from osteoarthritis and various inflammatory diseases. The morphologic criteria allowed the identification of subtypes, including phagocytic subtypes, among synoviocytic and monocytic cells in the fluids. The quantitative study showed an important afflux of monocytes and a hyperexfoliation of synoviocytes in the inflammatory diseases. In fluids with intermediate cellularity, the ratio of monocytes to synoviocytes allowed the differential cytodiagnosis between osteoarthrosis and arthritis. All monocytic subtypes, especially the phagocytic one, were highly significantly increased in the inflammatory diseases. A lower increase was shown by the synoviocytic subtypes, except the phagocytic one, which was not changed. Giant multinucleated synoviocytes were found in every type of disease and thus do not constitute a cytodiagnostic marker. Alcian blue staining without hyaluronidase treatment showed hyaluronate in only a small percentage of the synoviocytes. Cytoenzymologic study showed that synoviocytes and monocytes were positive for all tested hydrolases (beta glucuronidase, acid phosphatase and alpha naphthyl acetate esterase), with the reactivities always higher in the synoviocytes. The synoviocytes were always negative with peroxidase, so this reaction, although it marks only a minority of the monocytic population, can be used as an extra cytologic criterion for the discrimination of mononucleated cells in synovial fluid. There was no significant quantitative difference at the cellular level between osteoarthrosis and arthritides in the reaction to these four enzymes. The lysosomal enzymatic activity in both monocytic and synoviocytic cells confirmed their heterophagic properties. However, synoviocytic heterophagy seems to be a physiologic process, either little or not affected by inflammatory events. On the other hand, monocytic heterophagy and then the macrophagic transformation of monocytes appears to be a major aspect of intrasynovial inflammatory reactions. The question remains as to why, if a large majority of exfoliated synoviocytes comes from type A synovial-lining cells and if they belong to mononuclear phagocytic system, do they so weakly, or not at all, participate as phagocytes in the inflammatory reaction.     

Inhibition of endotoxin-induced monocytic procoagulant activity by n-alcohols and anesthetics.

1. The effect of n-alcohols (methanol and ethanol) and anesthetics (lidocaine, thiopental, methohexital and thiamylal) on procoagulant activity (PCA) in human peripheral-blood monocytes and non-adherent cultured leukemia promonocytic U937 and THP-1 cells was examined herein. 2. Exposure of whole blood to ethanol showed no effect on PCA in human monocytes. However, ethanol dose-dependently inhibited LPS-induced PCA in isolated human monocytes. 3. In THP-1 cells, ethanol had no significant effect on PCA in either non-challenged or LPS-induced status. However, the induction of PCA by LPS was substantially inhibited when cells were pretreated with 1% ethanol (v/v) for 72 hr. 4. In U937 cells, n-alcohols and anesthetics resulted in dose-dependent depressions in PCA. Importantly, the percent reduction in LPS-induced PCA was much more pronounced than that in non-challenged PCA. 5. These data clearly suggest that n-alcohols and anesthetics readily inhibit the LPS-stimulatory action on monocytic PCA.     

A human B lymphocyte antigen (P-76) shared by B-cell chronic lymphocytic leukemia cells and hairy cell leukemia cells

A membrane antigen with an apparent specificity to B lymphocytes was detected with immunochemical techniques and its properties were analyzed. Anti-B-CLL serum was raised in a rabbit by immunization with B-cell chronic lymphocytic leukemia (B-CLL) cells. This anti-B-CLL serum was absorbed with erythrocytes, liver homogenate and insolubilized immunoglobulins. After further absorption with T-CLL cells, chronic myelocytic leukemia (CML) cells and acute myelocytic leukemia (AML) cells, the anti-B-CLL serum still reacted with peripheral blood B lymphocytes, B-CLL cells and hairy cell leukemia (HCL) cells. In contrast, no reactivity was seen with peripheral blood T lymphocyte or monocytes, or leukemia cells of non-B cell origin. An immunoprecipitation of radiolabeled cell surface proteins was attempted using the anti-B-CLL serum in the presence of Staphylococcus Aureus Cowan 1 (SaCl), and the precipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A membrane antigen with an apparent molecular weight of 76,000 daltons (P-76) was immunoprecipitated with the anti-B-CLL serum from the lysates of normal B lymphocyte, B-CLL cells and HCL cells. The antigen (P-76) is not composed of disulfide-linked subunits and has no structural relationship with HLA-DR (Ia-like) antigens or other known antigens. These results suggest that this antigen is B-lymphocyte specific, and favour the B-lymphocyte nature of HCL cells.     

Characterization of effector cells with anti-Candida activity obtained from murine bone marrow cells cultured in the presence of rhG-CSF: comparison between normal and CY-treated mice

Bone marrow cells (BMC) obtained from normal and cyclophosphamide (CY)-treated mice were cultured in the presence of recombinant human granulocyte-colony stimulating factor (rhG-CSF) and their effector cell activities inhibiting growth of C. albicans were examined. When BMC from CY-treated mice were preincubated with 0.05 ng/ml of rhG-CSF, effector cells with enhanced anti-C. albicans activity were recovered in the adherent cell population, whereas anti-C. albicans activity of BMC from normal mice was found in the non-adherent cell population. During culture without the presence of rhG-CSF, nonadherent BMC, seemingly granulocytes, from normal mice showed apoptotic change, but addition of rhGCSF clearly inhibited this change. On the other hand, when BMC from CY-treated mice were cultured with rhG-CSF, adherent cells as the main effector had the appearance of monocytes. These differences between the effectors with anti-C. albicans activity obtained from normal and CY-treated mice are discussed.     

Activation of purified human thymus-derived (T) cells by mitogens. II. Monocyte- macrophage potentiation of mitogen-induced DNA synthesis.

Thymus-derived (T) cells from peripheral blood were purified by rosette formation with neuraminidase-treated sheep red blood cells (SRBC) and centifugation on Ficoll-Hypaque. T cells recovered from the pellet were freed of SRBC by treatment with Tris-NH4Cl. T cells purified by this method showed a diminished ability to take up 3H-thymidine (3H-TdR) after mitogen stimulation when compared to the mitogenic response of an equal number of autologous peripheral blood mononuclear lymphocytes (PBL). Autologous monocytes restored the capacity of purified T cells to take up 3H-TdR in the presence of phytohemagglutinin (PHA) or Concanavalin A (Con A). The effect was proportional to the number of monocytes added. Similar restorative effects could be obtained with allogeneic or xenogeneic monocytes. These data suggest that the mitogenic stimulation of human PBL and Con A may reflect the participation of more than one cell type: the T cells and monocyte and that the genetic origin of the monocyte is not critical for augmentation of the mitogenic activation of human T cells.     

Cadmium-induced synthesis of metallothioneins in human lymphocytes and monocytes

Cd2+-binding proteins of peripheral blood lymphocytes and monocytes have not well been characterized so far, although they are expected to be a clue for understanding Cd2+ toxicity in those immune competent cells. We separated a family of Cd2+-binding proteins from Cd2+-exposed human peripheral blood lymphocytes by gel filtration chromatography, and characterized them by SDS-gel electrophoresis. The proteins showed electrophoretic behaviours closely similar to metallothioneins (MTs) of HeLa cells derived from human cervical carcinoma. The proteins were also found in Cd2+-exposed monocytes, and were inducible by Cd2+ in both lymphocytes and monocytes. Anti-MT serum specifically precipitated these proteins, which were thus identified as MTs. These results suggest that the two classes of the cells involved in the immune system possess a protective mechanism against Cd2+ through MTs. A variety of human lymphoid cell lines derived from both T and B cells were also found to have capacity to synthesize MTs in response to Cd2+.     

Cellular origin and induction of pregnancy-associated alpha 2-glycoprotein synthesis in pregnant rats

The synthesis of alpha 2-PAG was measured and compared in tissues and cells from normal non-pregnant females, and maternal and fetal rats in vitro to define the target cells hormonally regulated during pregnancy. Synthesis was measured by [L-14C]leucine incorporation into immunochemically isolated alpha 2-PAG and confirmed by radioimmunodiffusion. alpha 2-PAG synthesis was demonstrated in maternal peripheral blood leucocytes, placenta, breast, spleen, liver and fetal peripheral blood leucocytes and liver. Maternal and fetal liver were the most active tissue producers and fetal liver synthesized 4 times more alpha 2-PAG than did maternal liver. Furthermore, fetal peripheral blood leucocytes synthesized 2 times more alpha 2-PAG per cell than did these same maternal cells. A direct comparison of synthesis by cells from pregnant and non-pregnant female rats revealed that (1) maternal peripheral blood leucocytes synthesized 5 times more alpha 2-PAG per cell than did normal leucocytes, although these same cells synthesized approximately equal amounts of total cell protein per cell, (2) maternal peritoneal exudate macrophages also synthesized 5 times more alpha 2-PAG per cell than did macrophages obtained from normal female rats, and total protein synthesis by these cells also closely paralleled each other, (3) maternal and fetal plastic-adherent peripheral blood monocytes synthesized 22 and 58 times more alpha 2-PAG per cell respectively than did normal monocytes, (4) maternal and fetal non-adherent lymphocytes synthesized 8 and 16 times more alpha 2-PAG per cell respectively than did normal lymphocytes and (5) fetal monocytes and lymphocytes synthesized 3 and 2 times more alpha 2-PAG per cell than did maternal monocytes and lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacterial, serum and cellular modulation of granulopoietic activity.

The interaction human peripheral blood lymphocytes, monocytes, gram-positive bacteria and human serum in the release of colony stimulating activity (CSA) has been studied. CSA was assayed by the soft agar technique using human and murine bone marrow cells. It has been demonstrated that gram-positive organisms and their products can stimulate release of CSA by mononuclear cells. Human serum is also effective in promoting release of CSA. Release is further modulated by interactions between lymphocytes and monocytes, and lymphocytes may serve to control the modulation. The serum component is sensitive to temperature inactivation suggesting that it may have a specific physiologic role in regulation. Bacterial products, on the other hand, are not subject to temperature inactivation and require the presence of human serum for activity to be expressed.     

The effect of TNF-alpha on glycosylation pathways in bovine synoviocytes.

Synoviocytes are fibroblastic cells that line joint cavities. These cells synthesize numerous cell-surface and extracellular-matrix glycoproteins that are required for maintenance of the joint. Joint inflammation, such as occurs in arthritis, has been shown to have major effects on synoviocyte proliferation and on the biosynthesis of glycoproteins. The structures of the carbohydrate moieties of glycoproteins, however, and the enzymes involved in their synthesis have not yet been described for synoviocytes. Therefore, to characterize the cell-surface glycoconjugates, synoviocytes were isolated from bovine ankles, and the cells were grown in primary cultures. Lectin-binding assays were used to identify exposed N- and O-glycan carbohydrate determinants on synoviocytes, and specific enzyme assays were used to identify some of the glycosyltransferases involved in the synthesis of the glycan chains. A number of the enzymes that synthesize N- and O-linked oligosaccharides were found to be active in cell-free extracts of synoviocytes, including those that synthesize core-1-based O-glycans and the more complex bi-antennary N-glycans. To understand the molecular events underlying the inflammatory response in the synovium of arthritis patients, we examined the effect of the inflammatory cytokine tumour necrosis factor alpha (TNF-alpha) on synoviocytes and on glycosylation profiles. TNF-alpha treatment, which induces apoptosis in synoviocytes, was accompanied by changes in lectin-binding patterns, indicating alterations in the expression of cell-surface oligosaccharides. Concurrently, changes in specific enzyme activities were observed in treated cells. Two enzymes potentially important to the inflammatory process, core 2 beta6-GlcNAc-transferase and beta4-Gal-transferase, increased after TNF-alpha treatment. This is the first study of glycoprotein biosynthesis in synoviocytes, and it shows that synoviocytes have a characteristic glycosylation phenotype that is altered in the presence of inflammatory cytokines.     

Effect of lectins on the interactions between human peripheral blood lymphocytes and monocytes

Interactions between normal human peripheral blood T lymphocytes and monocytes were investigated by measuring the in vitro cellular adherence of these cells in the presence and in the absence of mitogens. Concanavalin A (Con A), lentil lectin (Lc), and phytohemagglutinin (PHA) in mitogenic doses increased 15 to 20 times the binding of T lymphocytes to monocytes. The lectin-induced binding was similar to that produced by neuraminidase-gal-actose-oxidase treatment. A good correlation was found between the early cellular adherence induced by these lectins and by neuraminidase-galactose-oxidase and the blastogenesis of the T lymphocytes measured after 3 days of culture by [³H]thymidine uptake. However, wheat germ agglutinin (WGA), a nonmitogenic lectin, also increased the binding of T lymphocytes to monocytes. Addition of specific carbohydrates completely inhibited the cellular interactions induced by lectins. Peanut agglutinin (PNA) induced adherence of lymphocytes only after treatment of these cells with neuraminidase. Striking differences were not found between the lectin-induced adherence observed with autologous and heterologous cells. Killing of monocytes abolished entirely the lectin-induced adherence of lymphocytes, however killed T lymphocytes were still able to interact weakly with live monocytes. Dexamethasone was found to be a potent inhibitor of mitogen-induced cellular interactions.     

The cellular location and specificity of bacterial cytochrome c peroxidases.

We have found that an anti-CD11c monoclonal antibody (MAb) inhibits the respiratory burst induced in phorbol 12-myristate 13-acetate (PMA)-differentiated U937 cells as well as in human peripheral blood monocytes and neutrophils upon cell stimulation with concanavalin A. The MAb had no effect, however, when the added stimulus was fMet-Leu-Phe or PMA. Flow cytometry analyses indicated that concanavalin A was able to interact with CD11c. The anti-CD11c MAb inhibited significantly concanavalin A binding to differentiated U937 cells, and concanavalin A blocked binding of anti-CD11c MAb to the cells. Binding of labelled concanavalin A to membrane proteins which were separated by PAGE and transferred to nitrocellulose paper indicated that proteins with apparent molecular masses similar to those of CD11c (150 kDa) and CD18 (95 kDa) molecules were the main concanavalin A-binding proteins in differentiated U937 cells as well as in mature neutrophils. Similar experiments carried out in the presence of the anti-CD11c MAb showed a specific and significant inhibition of concanavalin A binding to the CD11c molecule. These results indicate that concanavalin A binds to the CD11c molecule and this binding is responsible for the concanavalin A-induced respiratory burst in PMA-differentiated U937 cells as well as in human mature monocytes and neutrophils.     

Use of a microtitre plate chemiluminescence reader to study surface phagocytosis by human monocytes

Human mononuclear cells were separated from freshly obtained peripheral venous blood by density centrifugation and the number of monocytes present estimated by volume spectroscopy. The mononuclear cells were then placed directly into the wells of a microtitre plate and incubated for one hour at 37°C to promote adherence of the monocytes to the plastic wells. Non-adherent cells were then removed by washing, thus avoiding the need to treat the monocytes with EDTA or other reagents during cell preparation. The time course and dynamics of the chemiluminescence response of adherent monocytes towards opsonized zymosan was similar to those seen using non-adherent cells. The ability of adherent monocyte preparations to produce chemiluminescence following incubation for varying periods with T-lymphocyte conditioned medium was investigated. The use of a microtitre plate chemiluminescence reader allows several plates to be assayed over the 24-hour period and since small numbers of cells are required, many cultures can be analysed in one experiment. This technique (Patent applied for) promises to be a powerful tool for dissecting the cellular events which occur during macrophage activation and examining the effect of various lymphokines on the ability of monocytes to produce a chemiluminescence response.     

Retinoic acid attenuates rheumatoid inflammation in mice

Retinoic acid is the active vitamin A derivative and is well-known to have diverse immunomodulatory actions. In this study, we investigated the impact of all-trans retinoic acid (ATRA), a biologic key metabolite of vitamin A, on the development of arthritis and the pathophysiologic mechanisms by which ATRA might have antiarthritic effects in animal model of rheumatoid arthritis (RA; collagen-induced arthritis [CIA] in DBA/1J mice). We showed that treatment with ATRA markedly suppressed the clinical and histologic signs of arthritis in the CIA mice. It reduced the expression of IL-17 in the arthritic joints. Interestingly, Foxp3(+) regulatory T cells were markedly increased and IL-17-producing CD4(+) T cells (Th17 cells) were decreased in the spleens of ATRA-treated mice. In vitro treatment with ATRA induced the expression of Foxp3 and repressed the IL-17 expression in the CD4(+) T cells in mice. ATRA suppressed the production of total IgG and IgG2a in splenocytes that were stimulated by LPS. It also reduced serum levels of total IgG and IgG2 anti-collagen Abs and germinal center formation in CIA mice. In addition, the ATRA-treated mice showed decreased osteoclast formation in arthritic joints. Moreover, ATRA downregulated the expression of receptor activator of NF-κB ligand, the leading player of osteoclastogenesis, in the CD4(+) T cells and fibroblast-like synoviocytes from patients with RA. Furthermore, ATRA prevented both human monocytes and mice bone marrow-derived monocytes/macrophage cells from differentiating into osteoclasts. These data suggest ATRA might be an effective treatment modality for RA patients.     

Antibody-dependent cellular cytotoxicity against HIV-coated target cells by peripheral blood monocytes from HIV seropositive asymptomatic patients

Cytotoxic effector cells like cytotoxic T cells, NK cells, monocytes/macrophages, and neutrophils can lyse directly HIV-infected or HIV-coated cells in the absence or presence of anti-HIV antibodies. Therefore, these cytotoxic mechanisms can be invoked either in the control of HIV infection at early stages of the disease or in the generalized immunosuppression observed at later stages of the disease. The relationship between anti-HIV effector mechanisms and disease, however, remains elusive. The present study investigates in HIV+ seropositive asymptomatic patients peripheral blood monocytes (PBM)-mediated antibody dependent cellular cytotoxicity (ADCC) against HIV-coated target cells in the presence of heterologous or autologous anti-HIV serum. To test for specific ADCC against HIV Ag, a T4+ CEM.TR line resistant to TNF and macrophage-mediated cytotoxicity was selected in vitro. ADCC was performed in an 18-h 51Cr-release assay using CEM.TR cells coated with inactivated HIV. Unlike PBM from normal controls, significant ADCC was observed by PBM from HIV+ seropositive patients in the presence of pooled HIV+ antiserum. The ADCC activity was specific for HIV and was dependent on the E:T ratio and the antiserum dilution used. Upon activation of PBM with rIFN-gamma, both normal and HIV+ PBM-mediated ADCC against HIV-coated CEM.TR. Furthermore, ADCC activity by PBM from HIV+ seropositive patients in the presence of their autologous serum was examined. Significant ADCC activity was observed and was dependent on the E:T ratio and serum dilution used. The findings demonstrating anti-HIV ADCC activity by PBM from HIV+ seropositive individuals and their autologous sera support the notion that monocyte-mediated ADCC may be operative in vivo.     

Lysis of uninfected HIV-1 gp120-coated peripheral blood-derived T lymphocytes by monocyte-mediated antibody-dependent cellular cytotoxicity

Abstract Previous reports from our laboratory have demonstrated that peripheral blood monocytes (PBM) from HIV-1 infected individuals are de novo activated and are cytotoxic in vitro. Significant monocyte-antibody-dependent cellular cytotoxicity (ADCC) was obtained against HIV-1 inactivated CD4⁺ CEM target cells coated with HIV-1 in the presence of autologous seropositive serum. Based on these findings, we hypothesized that in HIV-seropositive individuals the monocytes may play an important role in vivo in the autodestruction of non-infected CD4⁺ T lymphocytes. The present study was designed to test this hypothesis. Monocytes from normal donors activated with M-CSF lysed CD4+ T cells (CEM) coated with gp120 sensitized by plasma from asymptomatic HIV-1+ individuals in a 8 h ⁵¹Cr release assay. ADCC cytotoxic activity varied from one individual to another and was a function of the dilution of the individual seropositive plasma used. We then used circulating CD3+ T lymphocytes as targets for ADCC following treatment with actinomycin D to facilitate the release of radioactive ⁵¹Cr. Like CEM, ADCC was obtained with CD3⁺ T cells coated with gp120 in the presence of HIV seropositive plasma and monocytes. Lysis was specific as T cells that were not coated with gp120 were not destroyed. These findings demonstrate that activated peripheral blood derived monocytes can destroy non-infected gp120-coated circulating T lymphocytes by an ADCC-mediated mechanism. Thus, these findings suggest that ADCC may be one mechanism operating in vivo for the destruction of non-infected CD4⁺ T lymphocytes.     

Effect of the mitogen-activated kinase inhibitors on monocyte protein-1-stimulated chemotaxis of cells

Monocyte chemoattractant protein (MCP-1) is a major chemoattractant for monocytes and T-lymphocytes although it can cause migration of the HUVECs. We used monocytic cell line THP-1, monocytes of human peripheral blood, and HUVECs to study MCP-1 receptor-mediated cell migration. We showed that THP-1 and the monocytes chemotaxis was decreased in presence of specific inhibitors of p 38 MAP-kinase. Furthermore, it was almost completely diminished by inhibitor of tyrosine kinases. In contrast, MCP-1-stimulated migration of HUVECs was abrogated by specific inhibitor of ERK1/2 MAP-kinases and, to a lesser extent, by blocking tyrosine kinases. These results suggest that intracellular signal pathways activated by MCP-1 in monocytes and HUVECs, are distinct.     

IL‐17 induces osteoclastogenesis from human monocytes alone in the absence of osteoblasts,which is potently inhibited by anti‐TNF‐α antibody: A novel mechanism of osteoclastogenesis by IL‐17

IL‐17 is a proinflammatory cytokine crucial for osteoclastic bone resorption in the presence of osteoblasts or synoviocytes in rheumatoid arthritis. However, the role of IL‐17 in osteoclastogenesis from human monocytes alone remains unclear. Here, we investigated the role of IL‐17 in osteoclastogenesis from human monocytes alone and the direct effect of infliximab on the osteoclastogenesis induced by IL‐17. Human peripheral blood mononuclear cells (PBMC) were cultured for 3 days with M‐CSF. After non‐adherent cells were removed, IL‐17 was added with either infliximab or osteoprotegerin (OPG). Seven days later, adherent cells were stained for vitronectin receptor. On the other hand, CD11b‐positive monocytes purified from PBMC were also cultured and stained as described above. CD11b‐positive cells were cultured with TNF‐α and receptor activator of NF‐κB ligand (RANKL). In the cultures of both adherent cells and CD11b‐positive cells, IL‐17 dose‐dependently induced osteoclastogenesis in the absence of soluble‐RANKL. OPG or infliximab inhibited IL‐17‐induced osteoclastogenesis. Interestingly, in the culture of CD11b‐positive cells, the osteoclastogenesis was more potently inhibited by infliximab than by OPG. TNF‐α and RANKL synergistically induced osteoclastogenesis. The present study clearly demonstrated the novel mechanism by which IL‐17 directly induces osteoclastogenesis from human monocytes alone. In addition, infliximab potently inhibits the osteoclastogenesis directly induced by IL‐17. J. Cell. Biochem. 108: 947–955, 2009. © 2009 Wiley‐Liss, Inc.     

Incomplete growth of varicella-zoster virus in human monocytes

Infection of human peripheral blood monocytes by varicella-zoster virus (VZV) was investigated. When freshly isolated monocytes of young adult volunteers were infected with cell-free VZV and examined by indirect immunofluorescence, specific antigens appeared at 8 hr and the number of antigen-positive cells reached the maximum between 24 and 48 hr postinfection. The proportion of antigen-positive cells to total cells was similar to that of the permissive control (HeLa cells), while very few infectious centers (IC) of monocytes were formed in comparison with the infected control cells. Monocytes isolated from infants and old persons formed a larger number of IC than those of young adults. Electron microscopic study of VZV-infected monocytes from three young adult volunteers demonstrated that the proportion of VZV particle-positive cells to total cells was similar to that of antigen-positive cells, and most of the particles seen in the nuclei were low in density and lacked a central core. These results suggest that the growth of VZV in human adult monocytes is incomplete. This restriction of VZV growth by monocytes may play an important role in defense against VZV infection.