Biomedical subjects

M Lotz

Publications and source records attributed to M Lotz.

At least 127 records · Page 7Linked to original sources

PubMed1991

Epstein Barr virus/complement C3d receptor is an interferon alpha receptor.

Interferon alpha contains a sequence motif similar to the complement receptor type two (CR2/CD21) binding site on complement fragment C3d. Antibodies against a peptide with the CR2 binding sequence on C3d react with a peptide carrying the IFN alpha CR2 binding motif (residues 92-99) and with recombinant IFN alpha. The IFN alpha-derived peptide, as well as recombinant IFN alpha, inhibits C3bi/C3d interaction with CR2 on the Burkitt lymphoma Raji. The direct interaction of IFN alpha and CR2 is inhibited by polyclonal anti-IFN alpha, anti-CR2 and anti-C3d peptide antibodies as well as by C3bi/C3d, EBV coat protein gp350/220 and IFN but not by IFN gamma. [125I]IFN alpha binding to Raji cells is inhibited by polyclonal anti-IFN alpha and anti-CR2 antibodies, by peptides with the CR2 binding motif and partially by C3bi/C3d. Monoclonal anti-CR2 antibody HB5, but not OKB-7, blocks IFN alpha binding to Raji cells. CR2 or CR2-like molecules may therefore be the major IFN alpha receptors on B lymphocytes.

Amino Acid Sequence↗

PubMed1991

Interleukin-6 and transforming growth factor-beta synergistically stimulate chondrosarcoma cell proliferation.

This study examines the regulation of Swarm rat chondrosarcoma (SRC) cell proliferation in vitro. In serum-free cultures, SRC cells showed only transient DNA synthesis and this was increased by serum. Transforming growth factor-beta (TGF-beta) was identified as an essential serum component, since the mitogenic effect of sera was related to their TGF-beta content and neutralized by antibody to TGF-beta. Among a large panel of agents tested, TGF-beta was the only factor that stimulated proliferation in serum-free media. The TGF-beta isoforms TGF-beta 1 and TGF-beta 2 induced similar dose-dependent increases with maximal 62.5-fold stimulation at 10 ng/ml. Interleukin-6 (IL-6) was identified as a new factor that stimulated SRC proliferation. IL-6 effects were serum-dependent and their magnitude correlated with the TGF-beta content in different serum preparations. In serum-free cultures where IL-6 by itself had no detectable effect it caused up to 7.6-fold increased proliferation in the presence of small doses of TGF-beta (0.01-0.1 ng/ml). This synergy was unique, since no other factor tested synergized with IL-6 or TGF-beta. In examining potential mechanisms for this synergy it was found that TGF-beta increased IL-6 receptor expression. In summary, these results identify IL-6 as a new and TGF-beta as the most potent growth factor for chondrosarcoma cells and describe novel interactions between these factors in the regulation of cell growth.

Animals↗

PubMed1991

Transforming growth factor-beta and suppression of humoral immune responses in HIV infection.

We reported previously that PBMC from HIV+ patients spontaneously release increased levels of TGF beta 1, contributing to defects in cellular immune responses. This study defines the implications of TGF beta overexpression for humoral immunity in HIV infection. We found that upon Staphylococcus aureus Cowan I (SAC) stimulation of cells from HIV+ donors, B-lymphocyte proliferative responses were decreased. This deficiency correlated closely (r = 0.7, P less than 0.001) with increased TGF beta secretion by PBMC from HIV-infected donors. Conditioned medium from HIV+ PBMC and purified TGF beta 1 had similar inhibitory effects on SAC- or EBV-induced B-cell proliferation, and B cells from HIV-infected donors were as sensitive to inhibition by TGF beta as cells from normal donors. Antibodies to TGF beta 1 neutralized the inhibitory effect of HIV+ culture supernatants on normal B cells and increased low proliferative responses by HIV+ cells. Using PWM as stimulus for B cell differentiation, it was shown that activated TGF beta from HIV+ PBMC is able to significantly reduce the induction of immunoglobulins and this effect was also abrogated by anti-TGF beta. These studies support the concept that in HIV infection, TGF beta is a potent suppressor, not only of the cellular, but of the humoral immune responses as well.

Antibody Formation↗

PubMed1991

Differential processing of proenkephalin-A by human peripheral blood monocytes and T lymphocytes.

Human peripheral blood mononuclear cells are analyzed for preproenkephalin gene expression and peptide processing. Met-enkephalin immunoreactivity as detected with a specific antiserum is found in the cytoplasm of monocytes but not in T lymphocytes. Secretion of met-enkephalin was analyzed with an RIA that is specific for the met-enkephalin pentapeptide. Unfractionated PBMC spontaneously released 40 pg/ml met-enkephalin and this increased two- to fourfold after stimulation with PHA. Lower levels (less than 100 pg/ml) of met-enkephalin were detected in supernatants from purified T cells that were activated with PHA and IL-2. In contrast, stimulation of purified monocytes with LPS or PMA resulted in the release of up to 600 pg/ml of the processed peptide. To examine whether T cells can produce met-enkephalin precursor peptides, T cell conditioned media were treated with trypsin and carboxypeptidase-B, which is known to release met-enkephalin from the propeptide. This increased levels of met-enkephalin to 400 pg/ml, indicating that lymphocytes secrete the propeptide but do not process it to met-enkephalin. The 1.4-kb preproenkephalin mRNA is detected in activated blood mononuclear cells and in purified monocytes and T cells. To determine whether monocytes or lymphocytes express met-enkephalin in vivo, lymphoid tissues were analyzed by immunohistochemistry. In human spleen tissue, positive cells were found in the red pulp but not in the follicles, which is also consistent with met-enkephalin expression in monocytes. In summary, these results show that human peripheral blood mononuclear cells express preproenkephalin mRNA and that monocytes, but not T cells, process the propeptide to metenkephalin.

Adult↗

PubMed1991

[Modulation of immunocompetent cells in the synovial fluid TGF-beta].

Mononuclear cells (MNC) in synovial fluids from patients with rheumatoid arthritis and other arthropathies differ clearly from MNC in peripheral blood. Typically the ratio of CD4(+)-/CD8+ lymphocytes is inverted and the response to mitogens/cytokines (IL-1/IL-2) is impaired. Active TGF-beta (transforming growth factor beta) was found to account for these abnormalities, and the major isoform was identified as TGF-beta 2.

Arthritis, Rheumatoid↗

PubMed1990

Regulation of the hepatic synthesis of C1 inhibitor by the hepatocyte stimulating factors interleukin 6 and interferon gamma.

C1 inhibitor (C1INH), the major plasma inhibitor of activated C1, kallikrein, and activated Hageman factor, may be an important factor in limiting inflammatory injury mediated by the complement and contact systems. C1INH is thought to be synthesized primarily in the liver; however, the regulators of hepatic C1 inhibitor synthesis are completely unknown. In this report, we analyze the regulation of C1INH synthesis by hepatocyte stimulating factors in human hepatoma cell lines and primary hepatocytes. Interleukin-6 and interferon gamma increase C1INH production in both hepatoma cells and hepatocytes. These cytokines stimulate de novo synthesis of functional C1INH, acting at a pretranslational level as assessed by Northern blotting. The stimulatory effects of interleukin-6 and interferon gamma on C1INH synthesis are separate and are differentially modulated by interleukin-1. These results establish that hepatic C1INH synthesis is regulated by hepatocyte stimulating factors and reveal novel interactions between these factors.

Acute-Phase Proteins↗

PubMed1990

Transforming growth factor-beta and cellular immune responses in synovial fluids.

Mononuclear cells in synovial fluids (SF) from patients with rheumatoid arthritis and other arthropathies are characterized by functional and phenotypic changes, including impaired mitogen responsiveness and inverted ratios of CD4+/CD8+ T lymphocytes. This is related to previously described activities in synovial fluids that inhibit proliferation of lymphocytes induced by mitogens and cytokines. The present study examines the relationship of these activities and transforming growth factor beta (TGF-beta), which is now known as the most potent endogenous inhibitor of lymphocyte function. It is shown that most of the activity in SF that inhibits IL-1-induced thymocyte or T cell proliferation is neutralized by a specific antibody to TGF-beta. Analysis of the SF in the CCL64 assay, a standard test for TGF-beta, showed a close correlation between the levels of immunosuppressive activity and TGF-beta. SF contain spontaneously active inhibitors of T cell function and this is caused by the presence of active TGF-beta. Higher titers are found after transient acidification, which is known to activate the latent form of TGF-beta. Characterization of the TGF-beta isoforms showed that most of the material in SF is TGF-beta 2. Analysis of TGF-beta effects on T cell subsets demonstrated that it completely inhibits proliferation of CD4+ cells whereas at the same concentrations of purified or rTGF-beta CD8+ cells are only inhibited by maximally 31.1%. SF also preferentially inhibit CD4+ Th cell proliferation and this effect is neutralized by antibody to TGF-beta. Collectively these results indicate that the presence of TGF-beta accounts for most of the immunosuppressive activities in SF and that this factor may be responsible for functional and phenotypic changes of SF lymphocytes.

Arthritis, Rheumatoid↗

PubMed1990

IL-6 production by human articular chondrocytes. Modulation of its synthesis by cytokines, growth factors, and hormones in vitro.

IL-6 is a regulator of inflammatory and immunological processes and high levels of this cytokine have recently been shown to be present in synovial fluids from inflammatory and degenerative arthropathies. Synovial fluid IL-6 may in part be a product of synoviocytes that have previously been identified as a source of IL-6. To further define intraarticular sources of IL-6, we examined the ability of chondrocytes to produce IL-6 and studied its modulation by inflammatory cytokines and homeostatic regulators of chondrocyte function. Human articular chondrocytes isolated from normal and osteoarthritic joints released low levels of IL-6 when cultured in the presence of serum. The inflammatory cytokines IL-1, and, to a lesser extent, TNF-alpha and IFN-gamma increased IL-6 production. Among the growth factors known to act on chondrocytes, only transforming growth factor-beta, but not epidermal growth factor. fibroblast growth factor, insulin growth factor-1 and 2, platelet growth factor or insulin, was able to significantly increase IL-6 synthesis. Analysis of hormonal influences on chondrocyte IL-6 production showed that testosterone and estradiol synergized with IL-1 in the induction of IL-6. Hydrocortisone, at 10 ng/ml, reduced IL-1-induced IL-6 production by more than 50%. Chondrocyte-derived IL-6 stimulated acute phase protein synthesis and hybridoma cell proliferation. These biological activities were neutralized by a specific antibody to IL-6. Metabolic labeling and immunoprecipitation studies showed that IL-1 induced de novo synthesis of IL-6 and that the IL-6 proteins secreted by chondrocytes were similar to those from fibroblasts. These results demonstrate that chondrocytes are able to produce IL-6 in response to physiologic and inflammatory stimuli. Chondrocytes probably contribute to the increased synovial fluid levels of IL-6 in inflammatory and degenerative conditions of cartilage, and IL-6 may serve as a mediator to coordinate responses to cartilage injury.

Cartilage, Articular↗

PubMed1990

Autoantibody production by severe combined immunodeficient mice reconstituted with synovial cells from rheumatoid arthritis patients.

In an attempt to characterize the heterogeneity of the human autoantibody response, mice with severe combined immunodeficiency were reconstituted with synovial or blood lymphocytes from patients with rheumatoid arthritis (RA). Mononuclear cells extracted from synovial fluid or tissue (SMC) were a greatly enriched source of IgM rheumatoid factor (RF)-producing cells compared to the peripheral blood mononuclear cells (PBMC) of rheumatoid arthritis patients or normal donors. Six to nine weeks after reconstitution of mice with synovial mononuclear cells, 0%-39.3% (mean = 11.4%) of total IgM consisted of IgM RF compared to 0%-0.15% (mean = 0.02%) in mice given RA PBMC and 0%-1.2% (mean = 0.34%) in mice given normal PBMC. Detectable levels of IgM RF were maintained in some mice for as long as 20 weeks after transfer. Mice reconstituted with synovial membrane or synovial fluid lymphocytes produced a heterogeneous mixture of immunoglobulins. These included other autoantibodies, such as anti-nuclear and anti-cytoplasmic antibodies, and antibodies to exogenous antigens such as the Epstein-Barr virus nuclear antigen-1 (EBNA-1). This heterogeneity is further illustrated by the demonstration that the sera from mice given synovial cells also contained IgG antibodies possessing all three major VH families (VH1, VH3 and VH4) and the four major V kappa families (V kappa 1 to V kappa 4). Autoantibody production gradually decreased with time even under circumstances where total immunoglobulin levels increased, and elevated production could not be induced by antigenic stimulation. These findings describe a new model for the analysis of human autoantibody production.

Animals↗

PubMed1990

Transforming growth factor beta and noncytopathic mechanisms of immunodeficiency in human immunodeficiency virus infection.

This study examines the contribution of transforming growth factor beta (TGF beta), one of the most potent endogenous immunosuppressive factors, to the development of immunodeficiency in human immunodeficiency virus (HIV) infection. Increased titers of TGF beta were found in supernatants of peripheral blood mononuclear cells (PBMCs) from HIV-infected donors as compared to uninfected controls (P less than 0.001). This correlated closely with defective responses of CD4+ lymphocytes to the recall antigens tuberculin purified protein derivative or tetanus toxoid. The addition of TGF beta-neutralizing antibody to PBMCs partially restored these defective T-cell responses. Furthermore, purified TGF beta or HIV+ PBMC culture supernatants preferentially inhibited proliferation of CD4+ lymphocytes as compared to CD8+ cells. The increased expression of the TGF beta protein was associated with increased TGF beta mRNA as determined by a polymerase chain reaction assay. This increase in TGF beta protein and mRNA was due to a selective upregulation of the TGF beta 1 isoform. These results indicate that overexpression of TGF beta 1 occurs in HIV-infected individuals and that this cytokine can contribute to impaired immune functions and to depletion of CD4+ T lymphocytes.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Potent toxicity of 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo. A novel approach to immunosuppressive therapy.

Lymphoid cells were thought to be uniquely susceptible to excess 2'-deoxyadenosine (dAdo), when exposed to inhibitors of adenosine deaminase (ADA). However, we now find that human monocytes are as sensitive as lymphocytes to dAdo or to the ADA-resistant congener 2-chloro-2'-deoxyadenosine (CldAdo). Monocytes exposed in vitro to CldAdo, or to dAdo plus deoxycoformycin rapidly developed DNA strand breaks. Both the DNA damage and the toxicity of CldAdo or dAdo toward monocytes were blocked by deoxycytidine, but not by inhibitors of poly(ADP-ribose) polymerase. A partial decrease in RNA synthesis and a gradual decline of cellular NAD were early biochemical events associated with monocyte DNA damage. Low CldAdo concentrations (5-20 nM) inhibited monocyte phagocytosis and reduced the release of interleukin 6. Higher CldAdo concentrations led to a dose- and time-dependent loss of monocyte viability. Circulating monocytes disappeared within 1 wk in patients with cutaneous T cell lymphoma or with rheumatoid arthritis during continuous CldAdo infusion. The marked sensitivity of human monocyte function and survival to CldAdo in vitro, together with the monocyte depletion in patients receiving CldAdo chemotherapy, suggests that CldAdo or other dAdo analogues offer a novel therapeutic strategy for chronic inflammatory and autoimmune diseases characterized by inappropriate monocyte deployment or function.

2-Chloroadenosine↗

PubMed1989

Bacterial lipopolysaccharide and inflammatory mediators augment IL-6 secretion by human endothelial cells.

The interaction between human endothelial cells and leukocytes during immunologic and inflammatory responses is in part mediated through the release of soluble mediators. We report that cultured human umbilical vein endothelial cells secrete IL-6 when stimulated with LPS. This effect was inhibited by polymyxin-B. The monokines IL-1 and TNF-alpha were also potent inducers of IL-6, whereas lymphotoxin was only effective at much higher concentrations. Endothelial cell supernatant IL-6 was active as hybridoma-plasmacytoma growth factor and as B-cell stimulating factor. Endothelial IL-6 activity was neutralized by a specific anti-IL-6 antibody and by immunoprecipitation it was shown to be identical in size to human fibroblast-derived IL-6. As IL-6 is possibly an important regulator of host defense responses, production of this cytokine by endothelial cells may contribute to the pathogenesis of various inflammatory and immunologic diseases.

Adjuvants, Immunologic↗

PubMed1989

Inflammatory microcrystals stimulate interleukin-6 production and secretion by human monocytes and synoviocytes.

Crystal-related joint diseases are often associated with systemic inflammatory manifestations, including increased levels of acute-phase proteins, leukocytosis, and fever. Recently, interleukin-6 (IL-6) has been identified as a pluripotent mediator of inflammatory and immunologic responses and the major hepatocyte-stimulating factor. In this study, we demonstrated that monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals, and to a lesser extent, hydroxyapatite crystals, increased IL-6 production by synoviocytes and monocytes in vitro. Immunoprecipitation experiments showed that MSU and CPPD crystals, but not hydroxyapatite crystals, were able to increase the release of newly synthesized IL-6. Crystal-induced IL-6 stimulated acute-phase protein synthesis, immunoglobulin production, and hybridoma cell proliferation, which was neutralized by a specific antibody to IL-6. High levels of IL-6 were found in synovial fluid from patients with gout and pseudogout. These results demonstrate that MSU and CPPD crystals can induce IL-6 production in synoviocytes and monocytes, and that synovial fluid from patients with gout and pseudogout contains high levels of IL-6. Crystal-induced IL-6 is likely to be an important mediator of inflammatory responses in acute gout and pseudogout.

Calcium Pyrophosphate↗

PubMed1989

Profound toxicity of deoxyadenosine and 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo.

Deoxyadenosine is known to be toxic to both proliferating and resting lymphocytes that lack adenosine deaminase (ADA) activity. We now show that human monocytes are also highly sensitive in vitro to nanomolar concentrations of deoxyadenosine plus the ADA inhibitor deoxycoformycin, and to the ADA-resistant analogue 2-chlorodeoxyadenosine (CdA). Monocytes exposed to deoxyadenosine or to CdA in vitro accumulate massive DNA damage detectable within 1 hour. The DNA damage in monocytes exposed to CdA is associated with a decrease in protein synthesis and with inhibitions of phagocytosis and IL-6 secretion. However, unlike lymphocytes with similar DNA damage, the monocytes show no significant NAD or ATP depletion until cell viability declines. The selective toxicity of CdA to monocytes was confirmed by in vivo studies. In almost all patients receiving CdA infusion chemotherapy for cutaneous lymphoma, the blood monocytes counts fell to near 0 during one week of therapy. Our results suggest that CdA and related compounds may have potential clinical use in the therapy of immune disorders associated with monocyte/macrophage activation.

2-Chloroadenosine↗

PubMed1989

Epstein-Barr virus and rheumatoid arthritis: cellular and molecular aspects.

Several lines of research have indicated a possible association of the Epstein-Barr virus and rheumatoid arthritis (RA). The earliest evidence suggested that RA patients develop a stronger humoral immune response to EBV nuclear antigens (EBNA) which may in part account for the increased titers of antibody to the RA nuclear antigen (RANA). It was then pointed out that mononuclear cells from RA patients may be impaired in their capacity to control EBV infection. This may be related to a decrease in the production of IFN gamma and a consequence of monocyte-derived inhibitory activities. These cellular defects, however, are not specific for RA and may rather be the result of chronic inflammatory responses. These findings and the lack of increased virus presence in RA tissues did not provide a strong basis for a possible association of EBV and RA. A new concept for this association is now being tested on the basis of the sequence homology between the genetic RA susceptibility determinant HLA DR4 and the EBV glycoprotein 110.

Amino Acid Sequence↗

PubMed1989

Synovium as a source of interleukin 6 in vitro. Contribution to local and systemic manifestations of arthritis.

Synovial inflammation is often associated with systemic changes, such as increased levels of acute phase proteins and hypergammaglobulinemia, which cannot be explained by the cytokines described in synovial fluids and synoviocyte secretions. Interleukin 6 (IL-6) has recently been characterized as a mediator of multiple inflammatory responses. This cytokine promotes T and B lymphocyte growth and differentiation, and acute phase protein synthesis. We therefore examined IL-6 production by human synoviocytes and its presence in synovial fluids. In vitro, synoviocytes spontaneously released IL-6, which was increased by IL-1 and tumor necrosis factor-alpha. Synoviocyte-derived IL-6 activity was able to induce hybridoma-plasmacytoma proliferation, and immunoglobulin and acute-phase protein synthesis. The synovial fluids from patients with diverse arthropathies contained IL-6 activity, but higher levels were present in inflammatory arthropathies than in osteoarthritis. These results demonstrate that synoviocytes are a potent source of IL-6, which can contribute to important manifestations of inflammatory arthropathies.

Acute-Phase Proteins↗

PubMed1989

Human endothelial cells produce IL-6. Lack of responses to exogenous IL-6.

The interaction between human endothelial cells and leukocytes during immunological and inflammatory responses is in part mediated through the release of soluble mediators. We report that cultured human umbilical vein endothelial cells secrete IL-6 when stimulated with lipopolysaccharide. The monokines, IL-1 and TNF-alpha, were potent inducers of IL-6, whereas lymphotoxin was only effective at much higher concentrations. IFN gamma also was a strong stimulus of IL-6 production, but TGF-beta did not have an effect at doses modulating other endothelial cell functions. Endothelial cell IL-6 was active as hybridoma-plasmacytoma growth factor and as B-cell and hepatocyte stimulating factor. Endothelial IL-6 activity was neutralized by a specific antibody to IL-6 and it was shown by immunoprecipitation to be identical in size to human fibroblast-derived IL-6. IL-6 did not have a detectable effect on several endothelial cell functions, including proliferation, adherence of leukocytes, and synthesis of PGE2, TPA, and PAI-1. As IL-6 is probably an important regulator of host defense responses, production of this cytokine by endothelial cells may contribute to the pathogenesis of various inflammatory and immunologic diseases.

Animals↗

PubMed1988

Effect of neuropeptides on production of inflammatory cytokines by human monocytes.

Two groups of mediators, the neuropeptides substance P and K and the monocyte-derived cytokines, interact in the neural regulation of immunological and inflammatory responses. Substance P, substance K, and the carboxyl-terminal peptide SP(4-11) induce the release of interleukin-1, tumor necrosis factor-alpha, and interleukin-6 from human blood monocytes. The neuropeptide effects occur at low doses, are specific as shown by inhibition studies with a substance P antagonist, and require de novo protein synthesis. Since monocyte-derived cytokines regulate multiple cellular functions in inflammation and immunity and since neuropeptides can be released from peripheral nerve endings into surrounding tissues, these findings identify a potent mechanism for nervous system regulation of host defense responses.

Cells, Cultured↗