Autoreactive liver-infiltrating T cells in primary biliary cirrhosis recognize inner mitochondrial epitopes and the pyruvate dehydrogenase complex

Primary biliary cirrhosis (PBC) is characterized by lymphoid infiltrates in the portal tracts of the liver and the occurrence of antimitochondrial autoantibodies in serum directed against components of the pyruvate dehydrogenase complex and the other alpha-keto acid dehydrogenase complexes. These enzymes are located on the inner mitochondrial membrane. The destruction of the biliary tract in PBC is thought to be mediated by autoreactive liver-infiltrating T cells exerting cytotoxic activity or releasing certain lymphokines. In this study the reactivity of liver infiltrating T cells was shown to a bovine pyruvate dehydrogenase complex (PDH), a purified E2 subunit (PDH-E2) and a crude preparation of human liver mitoplasts (HLM), i.e. mitochondria depleted of their outer membranes. Peripheral blood lymphocytes (PBL) from 11 of 15 patients (73.3%) with PBC showed a HLA class II-restricted proliferative response to the PDH complex whereas PBL from patients with chronic viral hepatitis, autoimmune hepatitis or extrahepatic cholestatic icterus (n = 20) and healthy controls (n = 5) did not. In addition 13 of 15 PBL from patients with PBC (86.6%) and three of nine PBL from patients with autoimmune hepatitis (33.3%) reacted with the crude HLM preparation whereas no reactivity was found with PBL from eight patients with chronic viral hepatitis, three patients with extrahepatic cholestasis or five healthy controls. Clonal analysis of 115 liver-infiltrating T cells derived from two diagnostic liver biopsies of patients with PBC revealed a predominance of activated CD4+CD8- T helper cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Concomitant loss of conformation and superantigenic activity of staphylococcal enterotoxin B deletion mutant proteins

The T-cell-stimulating activity of staphylococcal enterotoxin B (SEB) is an important factor in the pathogenesis of certain staphylococcal diseases. To investigate the immunologically active domains of the SEB molecule, we have produced truncated fragments of recombinant SEB by C-terminal and N-terminal deletions. The fragments were expressed as fusion proteins with protein A, including a cleavage site to remove the protein A part. Mutant proteins were tested for the ability to stimulate human resting T cells and SEB-reactive T-cell clones. Deletion of only 9 amino acids from the C terminus leads to complete loss of T-cell-stimulating activity. Removing further amino acids from the SEB molecule did not lead to a reexpression of T-cell-mitogenic activity. A mutant protein, however, in which the 9 C-terminal amino acids were replaced with a tail of 68 amino acids encoded by the vector was fully active. Two mutant proteins with N-terminal deletions of 60 and 81 amino acids were inactive as well. A neutralizing monoclonal antibody against a conformational epitope lost binding with all the inactive mutant proteins only, whereas a monoclonal antibody recognizing an epitope involved in emetic activity reacted with all mutant proteins. These results suggest that even small deletions at the C terminus affect the three-dimensional conformation of the SEB molecule.

Stimulation of human T cells by streptococcal "superantigen" erythrogenic toxins (scarlet fever toxins)

The pyrogenic (erythrogenic) exotoxins A and C (SPEA and SPEC) of Streptococcus pyogenes belong to the family of mitogenic toxins of which the staphylococcal enterotoxins are the prototypes. The erythrogenic toxin B (SPEB) is a proteinase precursor. All SPE have been reported to be superantigens. Here we have analyzed the human T cell response to these toxins. We used highly purified preparations of SPEA, SPEB, and SPEC from different S. pyogenes strains. These toxins were apparently homogenous in SDS-PAGE, IEF, and HPLC. In addition, recombinant SPEA and SPEC were produced in Escherichia coli. In cultures of PBMC, all three toxins expanded preferentially a fraction of T cells. Using mAb against V beta 2, -5, -6, -8, and -12, we investigated the phenotype of the stimulated cells. Natural SPEA, SPEB, and SPEC strongly stimulated V beta 8+ T cells, whereas recombinant SPEA and SPEC did not. Both natural and recombinant SPEA stimulated V beta 12+ cells and both natural and recombinant SPEC stimulated V beta 2+ cells. In accordance with these findings, a human V beta 8+ line responded to all three toxins derived from S. pyogenes but not to the recombinant proteins. An antiserum against natural SPEC neutralized specifically the V beta 2-stimulating activity of SPEC and the V beta 8-stimulating activity of all three toxins, but had no effect on the response to other superantigens. This shows that trace amounts of a potent novel V beta 8-stimulating activity not identical to SPEA and SPEC are responsible for the stimulation of V beta 8+ T cells by natural SPEA and SPEC reported previously. In a preliminary screening of S. pyogenes strains from patients, we found that this novel superantigen appears to be more widely distributed than SPEA and SPEC. Furthermore, we present evidence that also the superantigenic properties of SPEB are due to contaminations with this V beta 8 stimulator. The response to SPEB usually required 1000 times higher concentrations than to SPEA or SPEC. Antisera to SPEC but not to SPEB inhibited the response of PBMC and V beta 8+ Jurkat cells to SPEB. Furthermore, more stringent purification of SPEB yielded SPEB preparations devoid of mitogenic activity. These results indicate that the mitogenicity that is commonly attributed to SPEB is due to minute contaminations of the V beta 8 stimulator. These results raise two important caveats for the work with these highly potent T cell mitogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of human T cells by streptococcal "superantigen" erythrogenic toxins (scarlet fever toxins)

The pyrogenic (erythrogenic) exotoxins A and C (SPEA and SPEC) of Streptococcus pyogenes belong to the family of mitogenic toxins of which the staphylococcal enterotoxins are the prototypes. The erythrogenic toxin B (SPEB) is a proteinase precursor. All SPE have been reported to be superantigens. Here we have analyzed the human T cell response to these toxins. We used highly purified preparations of SPEA, SPEB, and SPEC from different S. pyogenes strains. These toxins were apparently homogenous in SDS-PAGE, IEF, and HPLC. In addition, recombinant SPEA and SPEC were produced in Escherichia coli. In cultures of PBMC, all three toxins expanded preferentially a fraction of T cells. Using mAb against V beta 2, -5, -6, -8, and -12, we investigated the phenotype of the stimulated cells. Natural SPEA, SPEB, and SPEC strongly stimulated V beta 8+ T cells, whereas recombinant SPEA and SPEC did not. Both natural and recombinant SPEA stimulated V beta 12+ cells and both natural and recombinant SPEC stimulated V beta 2+ cells. In accordance with these findings, a human V beta 8+ line responded to all three toxins derived from S. pyogenes but not to the recombinant proteins. An antiserum against natural SPEC neutralized specifically the V beta 2-stimulating activity of SPEC and the V beta 8-stimulating activity of all three toxins, but had no effect on the response to other superantigens. This shows that trace amounts of a potent novel V beta 8-stimulating activity not identical to SPEA and SPEC are responsible for the stimulation of V beta 8+ T cells by natural SPEA and SPEC reported previously. In a preliminary screening of S. pyogenes strains from patients, we found that this novel superantigen appears to be more widely distributed than SPEA and SPEC. Furthermore, we present evidence that also the superantigenic properties of SPEB are due to contaminations with this V beta 8 stimulator. The response to SPEB usually required 1000 times higher concentrations than to SPEA or SPEC. Antisera to SPEC but not to SPEB inhibited the response of PBMC and V beta 8+ Jurkat cells to SPEB. Furthermore, more stringent purification of SPEB yielded SPEB preparations devoid of mitogenic activity. These results indicate that the mitogenicity that is commonly attributed to SPEB is due to minute contaminations of the V beta 8 stimulator. These results raise two important caveats for the work with these highly potent T cell mitogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Target sizes of galactosyltransferase, sialyltransferase, and uridine diphosphatase in Golgi apparatus of rat liver

Target inactivation analysis was used to measure the functional size of uridine diphosphogalactose: N-acetylglucosamine beta(1,4)galactosyltransferase (galactosyltransferase), cytidine monophospho-N-acetyl-neuraminic acid: beta-galactoside alpha(2,6) sialytransferase (sialyltransferase), and uridine diphosphatase (UDPase) in Golgi membranes isolated from rat liver. The size of nucleoside diphosphatase (NDPase), an enzyme similar to UDPase but localized in rat liver endoplasmic reticulum, was also estimated by target inactivation analysis. The related enzymes, UDPase and NDPase, have target sizes of 96 +/- 4 and 77 +/- 3 kDa, while galactosyltransferase and sialyltransferase have target sizes of 97 +/- 10 and 130 +/- 20 kDa, respectively. The target inactivation sizes of galactosyltransferase and of sialyltransferase are about twice the monomer molecular weights of these enzymes obtained from sedimentation studies of the solubilized membranes as well as those predicted from previously reported cDNA sequences. We conclude from our studies that galactosyltransferase and sialyltransferase probably function as dimers in the Golgi membrane.

Function of dipeptidyl peptidase IV (CD26, Tp103) in transfected human T cells

CD26 (Tp103) is a proteolytic enzyme (dipeptidyl peptidase IV) expressed on the T cell surface that defines an alternative activation signal for human T lymphocytes. It is absent from or present in only low amounts on resting T cells but it is expressed strongly after activation. Crosslinking of CD26/Tp103 via the monoclonal antibody CB.1 triggers functional activities in preactivated T cells. To study the molecular requirements for T cell activation via CD26 we transfected a cDNA encoding CD26 into several CD26-negative cells. In Jurkat T cell leukemia cells that normally do not express the CD26 antigen, the transfected CD26 molecule is functional because the monoclonal antibody CB.1 induces an increase of cytosolic Ca2+ concentration and IL-2 production. For this stimulatory effect a crosslinking of the monoclonal antibody CB.1 is necessary. After modulation of the TCR/CD3 complex the transfected Jurkat cells were insensitive to triggering via CD26. Moreover, a CD26-transfected TCR-negative variant of Jurkat cells did not respond to CD26 triggering despite high levels of expression of the molecule on their surface. These data demonstrate that the function of CD26/Tp103 is dependent on the expression of the T cell receptor complex. In search of a physiological function of CD26 we found a costimulatory effect of mAb CB.1 in combination with the nonstimulatory anti-CD3 antibody BMA030 and an additive effect in the response to the superantigen staphylococcal enterotoxin E. Transfected Jurkat cells, however, did not show a reproducibly enhanced responsiveness to the superantigen compared to that of untransfected cells.

Interleukin-5 is the predominant eosinophilopoietin produced by cloned T lymphocytes in hypereosinophilic syndrome

Cloned T lymphocytes (TLC) of the CD4+CD8- phenotype established from peripheral blood of a patient with idiopathic hypereosinophilic syndrome (HES) were found to release a lineage-specific eosinophilic colony-stimulating factor (Eo-CSF). The present study was undertaken to identify the lymphokine accounting for this Eo-CSF activity. Comparison of TLC-derived Eo-CSF with recombinant human interleukin-5 (rhIL-5), recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and recombinant human interleukin-3 (rhIL-3) by in vitro clonogenic assays revealed similar bioactivity of HES-derived Eo-CSF and IL-5. Neutralization studies using specific antibodies against IL-5, GM-CSF and IL-3 confirmed that IL-5 mainly accounts for the Eo-CSF activity in all 9 HES-derived TLC tested. Eosinophilic colony (CFU-Eo) formation supported by conditioned media of the TLC was significantly inhibited in all clones by addition of anti-IL-5 monoclonal antibody (MAB) to the conditioned media. Inhibition by anti-IL-5 MAB was specific and dose-dependent. In 2 of the 9 clones, anti-GM-CSF antibodies could partially neutralize the Eo-CSF activity in the conditioned media. In 4 clones, addition of a combination of anti-IL-5 MAB and anti-GM-CSF antiserum to the conditioned media reduced CFU-Eo formation significantly more than addition of anti-IL-5 MAB alone. In none of the TLC could a significant role for IL-3 in eosinophilic colony formation be shown. These results were confirmed at the mRNA level. Cytokine transcripts were detected by reverse transcription (RT) and subsequent polymerase chain reaction (PCR). Under the same experimental conditions, all HES-derived TLC, but only one third of tested TLC from healthy donors, expressed IL-5 mRNA 5 days after stimulation. In control TLC with inducible IL-5 mRNA expression, IL-5 transcripts were found for only 3 days after stimulation. In contrast, HES-derived TLC contained IL-5 mRNA at least until day 18 after restimulation. All HES clones expressed GM-CSF mRNA upon stimulation. Two HES-derived TLC were found to lack IL-3 mRNA even after stimulation. Whereas IL-5 was expressed abundantly in all HES-clones, the intensity of PCR products for GM-CSF and IL-3 showed striking differences. Our in vitro results suggest that IL-5 produced by activated CD4+ T lymphocytes plays a crucial role in the induction of eosinophilia in HES. In addition, GM-CSF but not IL-3 seems to contribute partially to the increased eosinophil production in HES.

[Infiltrating T-cells in primary biliary cirrhosis recognize mitochondrial epitopes]

The primary biliary cirrhosis (PBC) is characterized by lymphoid infiltrates in the portal tracts of the liver and occurrence of antimitochondrial autoantibodies (AMA) in serum directed against the pyruvate dehydrogenase complex or other enzyme complexes that are located on the inner mitochondrial membranes. The destruction of the biliary tracts is thought to be mediated by autoreactive liver infiltrating T-cells. In this study we demonstrate the reactivity of peripheral and liver-infiltrating T-cells against a crude preparation of human liver subcellular fractions measured by the tritium-thymidine uptake. Peripheral blood mononuclear cells (PBMC) from 13 of 15 patients with PBC and from 3 of 9 patients with chronic autoimmune hepatitis recognized human liver mitoplasts, i.e. mitochondria depleted of their outer membranes. PBMC from patients with chronic viral hepatitis B and C or with extrahepatic cholestatic icterus and PBMC from healthy controls did not recognize this antigen. Monoclonal antibodies against HLA-class II molecules blocked this proliferative response. Clonal analysis of 115 liver-infiltrating T-cells derived from two diagnostic liver biopsies of patients with PBC revealed a predominance of activated CD4+CD8- T helper cells. Six CD4- positive T-cell clones were reactive to the HLM preparation when the antigen was presented by autologous B cell lines. MAb against HLA-class II or HLA-DR inhibited the response whereas mAb against HLA-DP did not. These clones did not respond to other subcellular fractions of human liver tissue. We conclude that among liver-infiltrating T-cells in PBC autoreactive T-cells exist that recognize some epitopes on the inner mitochondrial membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiclonal synovial T cell response to Yersinia enterocolitica in reactive arthritis: the Yersinia 61-kDa heat-shock protein is not the major target antigen

The T cell response to bacterial antigens plays a major role in the pathogenesis of reactive arthritis (ReA) following enteric infections with Yersinia enterocolitica. To study the antigen specificity of the T cells at the site of inflammation, the response of cloned T cells from the synovial fluid of 2 patients with ReA to partially purified antigens of Yersinia enterocolitica was determined. The clones showed different patterns of response to various fractions, indicating a multiclonal response to Yersinia antigens, and these specificities differed in the 2 patients. Some T cells were specific for Y. enterocolitica; some cross-reacted with other enterobacteria. Proteins of 14 and 19 kDa could be identified as target antigens for the T cell clones, but no clone could be unequivocally found that reacted with the highly purified Yersinia 61-kDa heat shock protein. Thus, the inflammatory T cell response in the synovial fluid in ReA is multiclonal and not predominantly directed against the bacterial heat shock 61-kDa protein.

Hepatitis A: hepatotropism and influence on myelopoiesis

Immunopathologic mechanisms leading to liver tissue injury in hepatitis caused by hepatitis A virus (HAV) were studied in an autologous in vitro model. Data show virus-specific killing by liver-infiltrating T lymphocytes in man and support the hypothesis that hepatocellular damage as well as efficient elimination of virus-infected hepatocytes is mediated by HLA-restricted, HAV-specific CD8+ T lymphocytes. Furthermore, experimental results demonstrate that human interferon-gamma produced by HAV-specific T cells may act as a key factor in T-cell-promoted clearance of HAV-infected hepatocytes. Besides the well-known hepatotropism, the myelotropic properties of HAV have some important clinical implications. Perturbations of hematopoietic regulation, ranging from transient granulocytopenia to rare cases of bone marrow failure, are associated with HAV infection. In an attempt to elucidate the pathogenetic mechanisms, we could show a direct suppressive effect of HAV on human bone marrow progenitors and a significant progressive decline in these cells in HAV-infected long-term bone marrow cultures.

Dissociation of antigen-presenting capacity of astrocytes for peptide-antigens versus superantigens

Although superantigens and their molecular interactions with MHC class II molecules have been well characterized recently, little is known concerning the physiological function of different types of APC in inducing superantigen-mediated T cell activation. To evaluate the potential of nonhematopoetic cells to present superantigens to T cells, we have tested astrocytes as a typical "nonprofessional" APC. Although astrocytes can express appropriate levels of MHC class II products and adhesion molecules, they turned out to be unable to mediate superantigen-driven activation of normal T lymphocytes, even in the presence of rather high concentrations of toxins. In contrast, they could properly present equimolar amounts of nominal Ag to various Ag-specific T cell lines under the same experimental conditions. Inability of astrocytes to support T cell responses to superantigens could not be overcome by addition of cytokines IL-1 and IL-6. Binding studies with class II-expressing astrocytes revealed that T cell unresponsiveness was not due to a general failure of astrocytes to bind the superantigen. Moreover, the resulting SA-class II complex was recognizable by TCR, as demonstrated by the capacity to activate IL-2 secretion in T cell hybridomas. Our results extend previous studies demonstrating marked differences of various types of APC to trigger T cell responses to superantigens and describe for the first time a dissociation of the Ag-presenting capacity for peptide-Ag vs superantigen on an accessory cell.

Dissociation of antigen-presenting capacity of astrocytes for peptide-antigens versus superantigens

Although superantigens and their molecular interactions with MHC class II molecules have been well characterized recently, little is known concerning the physiological function of different types of APC in inducing superantigen-mediated T cell activation. To evaluate the potential of nonhematopoetic cells to present superantigens to T cells, we have tested astrocytes as a typical "nonprofessional" APC. Although astrocytes can express appropriate levels of MHC class II products and adhesion molecules, they turned out to be unable to mediate superantigen-driven activation of normal T lymphocytes, even in the presence of rather high concentrations of toxins. In contrast, they could properly present equimolar amounts of nominal Ag to various Ag-specific T cell lines under the same experimental conditions. Inability of astrocytes to support T cell responses to superantigens could not be overcome by addition of cytokines IL-1 and IL-6. Binding studies with class II-expressing astrocytes revealed that T cell unresponsiveness was not due to a general failure of astrocytes to bind the superantigen. Moreover, the resulting SA-class II complex was recognizable by TCR, as demonstrated by the capacity to activate IL-2 secretion in T cell hybridomas. Our results extend previous studies demonstrating marked differences of various types of APC to trigger T cell responses to superantigens and describe for the first time a dissociation of the Ag-presenting capacity for peptide-Ag vs superantigen on an accessory cell.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.