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Biomedical subjects

B Fleischer

Publications and source records attributed to B Fleischer.

At least 19 recordsLinked to original sources
PubMed1992

CD2-mediated autocrine growth of herpes virus saimiri-transformed human T lymphocytes.

Herpes virus saimiri (HVS) immortalizes T lymphocytes from a variety of primates and causes acute T cell lymphomas and leukemias in nonnatural primate hosts. Here we have analyzed the requirements for growth of three HVS-transformed human T cell lines. The cells expressed the phenotype of activated T cells: two were CD4+, and one was CD8+. All three cells responded to all allogeneic human cell lines tested with enhanced proliferation, production of interleukin 2 (IL-2), and increased expression of the IL-2 receptor. Binding of CD2 to its ligand CD58 was the critical event mediating stimulation because: (a) monoclonal antibodies (mAbs) to CD2 and to CD58, but not to a variety of other surface structures, blocked induced and spontaneous proliferation and IL-2 production; (b) only anti-CD2 mAbs were stimulatory if crosslinked; (c) a nonstimulatory cell was rendered stimulatory by CD58 transfection; and (d) the cells responded specifically to CD58 on sheep red blood cells. Growth of the cells required activation because cyclosporin A and FK506 blocked stimulator cell-induced IL-2 production and proliferation as well as the spontaneous growth of the lines. Antibodies to the IL-2 receptor reduced proliferation of the cells and blocked IL-2 utilization. Taken together, these results show that HVS-transformed T cells proliferate in response to CD2-mediated contact with stimulator cells or with each other in an IL-2-dependent fashion. They suggest that HVS transforms human T cells to an activation-dependent autocrine growth.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Predominance of Th1-type T cells in synovial fluid of patients with Yersinia-induced reactive arthritis.

The pathogenetic mechanisms underlying the development of reactive arthritis and the functional capacities of synovial T cells specific for Yersinia enterocolitica are still unclear. In this study we have determined the cytokine secretion patterns of 24 CD4+ synovial fluid (SF)-derived T cell clones from 2 patients with Yersinia-induced reactive arthritis, 16 clones specific for different Yersinia antigens and 8 clones as controls. The clones specific for Yersinia antigens predominantly belong to the T helper cell 1 (Th1) subset with production of interferon (IFN)-gamma and interleukin (IL)-2, but no IL-4, whereas SF T cells not reactive with Yersinia antigens produce IL-2, IL-4 and IFN-gamma and thus belonged to the Th0 subset. Moreover, short-term T cell lines established from SF and peripheral blood showed the same pattern. To further analyze the functional relevance of these data we investigated the influence of IFN-gamma and IL-4 on the intracellular killing of Yersinia in a human glioblastoma cell line. Our data show that the Th1 cytokine IFN-gamma promotes intracellular killing of Yersinia, whereas this effect is antagonized by the Th2 cytokine IL-4. Furthermore, the Th2 cytokine IL-10 inhibited the antigen-specific proliferative response and IFN-gamma and IL-2 production by the Th1 cells. These results provide insight into the antibacterial mechanisms at work in reactive arthritis after infection with Yersinia enterocolitica and, for the first time, reveal the cross-regulatory properties of cytokines derived from Th1 and Th2 cells in a human immune response to bacterial antigens.

Adult↗
PubMed1992

Immune pathogenesis of hepatitis A.

In an effort to elucidate the mechanism of liver damage resulting from Hepatitis A virus (HAV) infection, we have studied infected skin fibroblasts and autologous lymphocytes from HAV patients. We report here that HLA-restricted virus-specific T cells play an essential role in HAV-related hepatocellular injury.

Fibroblasts↗
PubMed1992

Recombinant epidermolytic (exfoliative) toxin A of Staphylococcus aureus is not a superantigen.

The epidermolytic (exfoliative) toxins produced by Staphylococcus aureus cause epidermolysis and skin blistering. In addition, they have been implicated to belong to the group of T lymphocyte stimulating molecules known as "superantigens". Here we show that recombinant epidermolytic toxin A produced in S. aureus is not mitogenic for human and murine T lymphocytes. We discuss the possibility that minute contaminations of highly mitogenic exoproteins may cause the mitogenicity in several proteins that are reported to be superantigens.

Animals↗
PubMed1992

MHC-unrestricted recognition of bacteria-infected target cells by human CD8+ cytotoxic T lymphocytes.

A CD8+ alpha beta TCR+ T cell clone (A35) was isolated from the synovial fluid of a patient with post-enteric reactive arthritis caused by Yersinia enterocolitica. This clone efficiently killed autologous and allogeneic target cells that had been preincubated with live but not with heat-killed bacteria. There was no restriction by polymorphic parts of HLA-A, -B, or -C molecules and a HLA class II-deficient mutant cell line was lysed as efficiently as its normal counterpart, whereas infected HLA class I-deficient cells (Daudi cells) were not. The clone showed crossreaction between Yersinia enterocolitica, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes, but did not lyse target cells preincubated with Staphylococcus epidermidis. MAb to CD2, CD3, and CD8 efficiently blocked A35, whereas the addition of mAb to HLA class II or to HLA class I did not. This clone apparently represents a novel effector mechanism against bacteria-infected or -modified cells that could be involved in the immunopathology of reactive arthritis.

Adult↗
PubMed1992

Stimulator cell-dependent requirement for CD2- and LFA-1-mediated adhesions in T lymphocyte activation by superantigenic toxins.

The staphylococcal enterotoxins and related microbial T cell mitogens stimulate T cells by cross-linking variable parts of the T cell receptor (TCR) with MHC class II molecules on accessory or target cells. We have used cloned human T cells and defined tumor cells as accessory cells (AC) to study the requirements for T cell activation by these toxins. On AC expressing high levels of CD54 (intercellular adhesion molecule-1, ICAM-1) and CD58 (lymphocyte function-associated antigen-3, LFA-3), mAb to CD2 were relatively ineffective in inhibiting the response to the toxins and antibodies to the lymphocyte function-associated antigen-1 (LFA-1) did not inhibit at all. If added together, however, these mAb inhibited the response completely. Similar results were obtained using antibodies to the target structures of CD2 and LFA-1. In contrast, on cells expressing low levels of LFA-3, mAb to LFA-1 but not to CD2 were strongly inhibitory. The same pattern of inhibition was found when these same cells were used as presenters of specific antigen to the T cells. These data show that adhesions via CD2 or LFA-1 are alternatively required for the stimulation of the T cells by superantigenic toxins and demonstrate another similarity between T cell stimulation by superantigens and by specific antigen recognition.

Antigen-Presenting Cells↗
PubMed1992

Hepatitis C virus antibody secretion in vitro by peripheral blood lymphocytes.

A recombinant polypeptide corresponding to a virus-specific cDNA clone (c100-3) serves as the antigen for a hepatitis C virus (HCV) antibody assay. Previous investigations have shown an 80% prevalence of HCV antibodies in sera of patients suffering from post-transfusional chronic hepatitis non-A, non-B, but positive results were also obtained for 30 to 70% of sera from patients with chronic hepatitis B or autoimmune hepatitis. In this study we show that HCV antibodies are secreted by peripheral blood lymphocytes (PBL) in vitro. PBL from 12/35 patients with chronic non-A, non-B hepatitis and 1/6 patients with chronic active hepatitis B spontaneously secreted HCV antibodies in cell culture supernatants. The results were confirmed by neutralisation assay and ELISAs using recombinant and synthetic polypeptides derived from the c100-3 antigen and from the HCV core antigen. Two patients suffering from non-A, non-B hepatitis were negative for HCV antibodies in serum, but their PBL produced HCV c100-3 antibodies in vitro. PBL from patients suffering from autoimmune chronic hepatitis, primary biliary cirrhosis, toxic-liver injury and healthy blood donors did not produce antibodies to HCV c100 antigen irrespective of HCV antibody test results in their sera. Polyclonal B cell activation or mitogenic stimulation of T helper cells led to increased immunoglobulin synthesis by PBL in vitro, but did not lead to enhancement of specific HCV antibody production. In addition, HCV antibody production was not induced by these stimulation procedures in control lymphocytes. This spontaneous HCV antibody production in vitro suggests persistent antigenic stimulation of the B cells in vivo.

B-Lymphocytes↗
PubMed1992

Superantigens.

The endogenous superantigens (the enigmatic minor lymphocyte-stimulating antigens) have been identified; they are encoded by integrated mouse mammary tumor viruses. The retroviral superantigens appear to be transmembrane glycoproteins, and their highly variable extracellular carboxyl terminus is responsible for V beta interaction. In spite of intensive efforts the precise structure-function relationship for the superantigens is not yet clear. The most important consequences of the introduction of the superantigens in vivo are shock and T-cell depletion and anergy. The search for novel superantigens related to human diseases has started.

Animals↗
PubMed1992

Protection from experimental allergic encephalomyelitis by application of a bacterial superantigen.

Certain bacterial and viral T cell stimulating proteins ('superantigens') are known to be very potent activators of T cells with certain V beta receptors. When applied in vivo these molecules induce anergy in those T cells responding to them. In this study we have investigated the influence of staphylococcal enterotoxins (SE) on myelin basic protein (MBP)-specific T cells in Lewis rats. As MBP-specific T cells in rats belong exclusively to the V beta 8.2+ CD4+ subset, the induction of experimental allergic encephalomyelitis (EAE) allows for an estimation of the functional state of the respective V beta-bearing T cells after enterotoxin-induced activation. In vitro, various MBP-specific T cell lines showed a strong selective proliferative response to staphylococcal enterotoxin E (SEE) but not to other SE. The in vitro activation by SEE induced encephalitogenic potential in these cells. After application of SEE to Lewis rats the susceptibility to induction of EAE was completely abrogated. Such SEE-treated and MBP-challenged rats did not exhibit any signs of disease and their T cells did not respond to MBP in proliferation tests. This abrogation of EAE was only found with a superantigen capable of interacting specifically with V beta 8.2+ T cells. Superantigen-mediated induction of unresponsiveness may have relevance for the analysis of pathogenetic mechanisms and for therapeutic considerations in certain T cell-mediated autoimmune diseases.

Animals↗
PubMed1992

Stimulation of synovial fluid mononuclear cells with the human 65-kD heat shock protein or with live enterobacteria leads to preferential expansion of TCR-gamma delta+ lymphocytes.

T lymphocyte responses to heterologous or self 65-kD heat shock protein (hsp) have been implicated in the pathogenesis of various forms of arthritis. To delineate the relationship of 65-kD hsp to different synovial fluid (SF) T cell subsets, we stimulated synovial fluid (SFMC) and peripheral blood mononuclear cells (PBMC) from patients with different inflammatory rheumatic diseases and from healthy controls with human or mycobacterial 65-kD hsp, tetanus toxoid (TT), heat-killed or live Yersinia enterocolitica. Phenotyping of the resulting T cell lines revealed an increase of up to 97% TCR-gamma delta+ lymphocytes in the 65-kD hsp-stimulated SF-derived lines. This expansion of TCR-gamma delta+ cells was less pronounced with cultures of PBMC. A preferential expansion of TCR-gamma delta+ cells was also shown after SFMC stimulation with live, but not with heat-killed Yersinia or with TT. We conclude that a common mechanism is involved in the selective expansion of TCR-gamma delta+ lymphocytes upon SFMC infection with live Yersinia or upon contact with 65-kD hsp. Out of a panel of TCR-gamma delta+ T lymphocyte clones (TLC) derived from a human 65-kD hsp-stimulated line, only a minority of TLC proliferated weakly upon restimulation with this antigen in the presence of autologous monocytes, whereas TCR-alpha beta+ TLC responded vigorously to the human 65-kD hsp and in some cases also cross-recognized the mycobacterial hsp homologue and/or heat-killed Yersinia. This implies that additional factors or cells may be present in the milieu of SFMC cultures that propagate the expansion of TCR-gamma delta+ cells in response to 65-kD hsp or live bacteria.

Cell Line↗
PubMed1992

Separation of T-cell-stimulating activity from streptococcal M protein.

The superantigenic properties of M protein type 5 of Streptococcus pyogenes have been implicated as an important pathogenicity factor in streptococcal autoimmune diseases. Here we show that after a single purification step by affinity chromatography on immobilized albumin or fibrinogen, M protein has no mitogenic activity for T cells. We demonstrate that the superantigenicity of M proteins of type 5 and type 1 is due to contamination with the highly potent pyrogenic exotoxins of S. pyogenes in the range of 0.1 to 0.01%. These results raise a general caveat for work with these extremely active T-cell mitogens, because the mitogenicity of other streptococcal or staphylococcal proteins could be due to similar minute contamination with potent superantigens that are undetectable by any biochemical method but extremely effective in stimulating sensitive T cells.

Antigens, Bacterial↗
PubMed1992

Functional localization of an exocytosis-triggering G-protein in human cytotoxic T lymphocytes.

Human cloned CD8+ cytotoxic T lymphocytes permeabilized with alpha-toxin of Staphylococcus aureus can be triggered by the guanosine triphosphate (GTP) analogue GTP gamma S to release the contents of their granula by exocytosis. To localize the guanosine nucleotide-binding protein (G-protein) activated by GTP gamma S in the sequence of events after T-lymphocyte triggering we have used several inhibitors of T-cell activation that inhibit early stages in T-cell triggering. The protein kinase C-inhibitor staurosporine, the immunosuppressants cyclosporin A and FK-506 and genistein, an inhibitor of tyrosine kinases, all inhibited esterase release triggered in intact cells by anti-T-cell receptor antibodies but not GTP gamma S-induced release from permeabilized cells. Cyclosporin A, FK-506 and genistein also blocked exocytosis triggered in intact cells by a combination of phorbolester and the calcium ionophore A23187. In addition, cytochalasin B, an inhibitor of actin polymerization, inhibited exocytosis in intact cells but enhanced exocytosis from permeabilized cells. These data show that the G-protein effecting exocytosis is localized distally in the cascade of events after T-cell activation.

Alkaloids↗
PubMed1992

HLA-DP restricted Chlamydia trachomatis specific synovial fluid T cell clones in Chlamydia induced Reiter's disease.

Synovial fluid (SF) mononuclear cells from a patient with Chlamydia trachomatis induced acute Reiter's disease were directly by limiting dilution in a representative protocol using phytohemagglutinin in the cloning medium. Out of 76 alpha beta-TCR+ CD4+ T lymphocyte clones, 7 were shown to specifically recognize C. trachomatis in a proliferation assay. The antigen recognition of these clones was HLA-DP restricted. Unexpectedly, 2 HLA-DR restricted clones showed a proliferative response to Yersinia enterocolitica O3, though the patient had no history of yersinia infection. The high frequency of SF derived T cells with specificity for species-specific chlamydial antigens and the limited diversity of HLA class II restriction of these clones may indicate an oligoclonal synovial T cell response to persistent intraarticular chlamydia.

Adult↗
PubMed1991

Reactivity of infiltrating T lymphocytes with microbial antigens in Crohn's disease.

Intestinal T lymphocytes are normally unresponsive to microbial and recall antigens in vitro, whereas the same antigens induce strong immune responses in peripheral-blood-derived T cells. We obtained T lymphocytes from peripheral blood and from the non-inflamed and inflamed intestinal mucosa of 6 patients (3 male, 3 female; mean age 33 years) with Crohn's disease. The T cells were stimulated in vitro with a range of microbial antigens. Whereas T cells from normal mucosa were unresponsive, those from inflamed mucosa had a proliferative response comparable to that of the peripheral-blood-derived T cells. These findings suggest that physiologic unresponsiveness to luminal antigens is abrogated in the inflammatory lesions of Crohn's disease patients. Infiltrating T lymphocytes may therefore mediate chronic inflammation on encountering the many antigens present in the intestine.

Adult↗
PubMed1991

Selective loss of pertussis toxin-sensitive G-proteins from the plasma membrane after antibody-induced internalization of T-cell surface molecules.

Antibody-induced antigenic modulation occurs after binding of antibodies to a variety of cell surface proteins. It is characterized by aggregation and subsequent loss of the molecules from the cell surface, usually by internalization. In this study we have investigated the effect of modulation of the T-cell antigen receptor complex (TCR) and the transferrin receptor (TFR) on the distribution of cholera toxin (CTx)- and pertussis toxin (PTx)-sensitive GTP binding proteins in human T-lymphocytes. Modulation of both the TCR and the TFR induced a selective shift of PTx-sensitive G-proteins from the plasma membrane to a high density membrane fraction enriched for lysosomal membranes. The distribution of CTx-sensitive G-proteins was unaffected. This shift was found in both the T-cell leukemia line Jurkat and in normal T-cells. The loss of PTx-sensitive G-proteins from the plasma membrane required approximately 15 h to be complete and was not inhibited by cycloheximide. It had no influence on T-cell triggering via anti-T-cell receptor antibodies and is unrelated to the inactivating effect of TCR-modulation on T-cell signalling. The loss of PTx-sensitive G-proteins was not accompanied by greater sensitivity to stimuli raising cAMP concentration. These results show that PTx-sensitive G-proteins can be selectively depleted from the plasma membrane by antibody treatment of T-cells.

Adenosine Diphosphate Ribose↗
PubMed1991

An evolutionary conserved mechanism of T cell activation by microbial toxins. Evidence for different affinities of T cell receptor-toxin interaction.

The enterotoxins produced by Staphylococcus aureus are the most potent mitogens known. They belong to a group of distantly related mitogenic toxins that differ in other biologic activities. In this study we have compared the molecular mechanisms by which these mitogens activate human T lymphocytes. We used the staphylococcal enterotoxins A to E, the staphylococcal toxic shock syndrome toxin, the streptococcal erythrogenic toxins A and C (scarlet fever toxins, erythrogenic toxins (ET)A, ETC), and the soluble mitogen produced by Mycoplasma arthritidis. We found that all these toxins can activate both CD4+ and CD8+ T cells and require MHC class II expression on accessory and target cells. However, T cells could be activated in the absence of class II molecules if the toxins ETA or SEB were co-cross-linked on beads together with anti-CD8 or anti-CD2 antibodies. Enterotoxins, toxic shock syndrome toxin and scarlet toxins stimulate a major fraction of human T cells, and show preferential, but not exclusive, stimulation of T cells carrying certain TCR V beta. In contrast, the mitogen of M. arthritidis, a pathogen for rodents stimulates only a minority of human T cells but activates a major fraction of murine T cells. Analysis of human T cell clones expressing V beta 5 or V beta 8 TCR showed that these clones responded also to those toxins that did not stimulate V beta 5+ and V beta 8+ T cells in bulk cultures. These results indicate that different TCR bind to these toxins with different affinities and that the specificity of the TCR-V beta-toxin interaction is quantitative rather than qualitative in nature. Taken together our findings suggest that these toxins use a common mechanism of T cell activation. They are functionally bivalent proteins crosslinking MHC class II molecules with variable parts of the TCR. Besides V beta, other parts of the TCR must be involved in this binding. The finding that murine T cells responded more weakly to the toxins produced by the human-pathogenic bacteria than to the Mycoplasma mitogen could indicate that the toxins have been adapted to the host's immune system in evolution.

Animals↗
PubMed1991

Evidence for T cell receptor-HLA class II molecule interaction in the response to superantigenic bacterial toxins.

The staphylococcal enterotoxins and related microbial T cell mitogens stimulate T cells by cross-linking variable parts of the T cell receptor (TcR) with MHC class II molecules on accessory or target cells. In this report we describe that a given combination of T cell, accessory cell (AC) and toxin can be non-stimulatory. However, the same T cell can respond to the same toxin on another AC and the same AC can present the same toxin to another T cell. This indicates that in the complex formed between TcR, toxin and class II molecule an interaction between TcR and class II molecule takes place.

Antigen-Presenting Cells↗