The differential effects of hydrocortisone on activation and tolerance induction in human T lymphocyte clones

The in vitro effects of hydrocortisone on T cell activation and tolerance induction were investigated using human influenza virus immune T cell lines and clones. Hydrocortisone at 10⁻⁹ to 10⁻⁶ molar concentrations was able to inhibit the antigen induced but not the T cell growth factor (TCGF) mediated proliferative response of both the lines and clones. However, hydrocortisone was able to inhibit TCGF production by cloned T cells. The proliferative response of cloned T cells to intact influenza virus A/Texas/1/77 was more markedly inhibited by equivalent concentrations of hydrocortisone than was the response of that clone to a 24 amino acid sequence (p20) of the haemagglutinin molecule implying that hydrocortisone may also act at the level of antigen processing. Furthermore hydrocortisone was able neither to induce T cell tolerance alone nor to inhibit antigen specific tolerance induction. However, hydrocortisone did lower the antigen threshold for tolerance induction. The possible mechanisms of hydrocortisone activity in the modulation of T cell regulation in autoimmune disease are discussed.     

Inhibition of T cell proliferation specific for acetylcholine receptor epitopes related to myasthenia gravis with antibody to T cell receptor or with competitive synthetic polymers.

Long-term T cell lines and clones of C3H.SW origin specific to synthetic peptides representing immunogenic epitopes of the human aetylcholine receptor alpha-subunit were established. Using these lines and clones, it was possible to characterize the T cell recognition process of myasthenic epitopes. Testing a panel of N-and/or C-terminal truncated peptides it could be demonstrated that the deletion of the two C-terminal amino acids of peptides p195-212 and p259-271 resulted in a loss or reduction of the stimulatory capacity of the peptides towards the specific T cell lines. In contrast, no substantial effect on the stimulation of the line could be observed by shortening peptide p195-212 by up to five amino acids at the N-terminal end. The proliferation of T cell lines and clones specific to peptide p195-212 was inhibited by a mAb directed against the V beta 8 region of the T cell receptor. Furthermore, it was possible to block the peptide-specific proliferative responses of the lines and clones by the I-Ab restricted synthetic polypeptide (T, G)-A--L but not by the I-Ak restricted polypeptide antigen (H,G)-A--L. Similarly, p195-212 inhibited the proliferative response of the TCSW259-271 T cell line and p259-271 inhibited the specific proliferative response of the TCSW195-212 line. Moreover, the C-terminal shortened peptides inhibited significantly the in vitro stimulation of the T cell lines by the immunogenic peptides p195-212 and p259-271. The inhibition by the synthetic peptides or by (T,G)-A--L may be due to competitive blockade of the MHC binding site for the T cell line stimulating AChR peptides.     

Cyclosporine A and prednisolone inhibit lectin- and alloantigen-induced release of sCD8: correlation with proliferative responses

It has been shown previously that there is a strong correlation between the in vitro release of soluble CD8 glycoprotein (sCD8) and CD8+ T lymphocyte activation. In the present study, the lectin stimulation of peripheral blood mononuclear cells (PBMC) induced a dose-dependent release of sCD8 which correlated with the magnitude of CD8 lymphocyte activation as measured by the expression of the interleukin 2 (IL-2) receptor and HLA-DR antigen and of the T cell proliferative responses. Both the proliferative responses and the release of sCD8 were inhibited by cyclosporine A (CyA) and prednisolone (PRED) in a concentration-dependent manner. When the immunosuppressants were present for only 60 min before the initiation of the cultures, an inhibitory effect was also seen, but this was maximal only when the agents were added at the initiation of the culture period; when the addition of CyA or PRED was delayed for either 24 or 48 hr after the initiation of the culture, the degree of inhibition of the proliferative response was greatly reduced. However, there was a significant inhibition of sCD8 release by CyA even when it was added 48 hr after the culture initiation. The addition of recombinant IL-2 did not affect the lectin-induced sCD8 release. The inhibition of the lectin-induced proliferative response and sCD8 release by PRED, but not that by CyA, was reversed by the recombinant IL-2. Alloantigen stimulation also induced sCD8 release and this release was inhibited both by CyA and by PRED. These data, together with the known effects of CyA on differentiation, clonal amplification, and activation of CD8 T lymphocytes, suggest that in vitro sCD8 release occurs during the early stages of activation of CD8+ cytotoxic T cells.     

Polyclonal in vitro proliferative responses from nonimmune donors to Plasmodium falciparum malaria antigens require UCHL1+ (memory) T cells.

The in vitro polyclonal proliferative responses of peripheral blood mononuclear cells to whole blood stage parasites or fractionated antigens from the human malaria parasite Plasmodium falciparum were studied. Cells from healthy laboratory donors who had never been exposed to malaria antigens in vivo consistently proliferated to P. falciparum antigens, as did cord blood mononuclear cells. This response was only observed in sheep rosette-positive cells in the presence of adherent cells and was inhibited by NH4Cl, indicating a requirement for antigen processing. The proliferative response was strongest at day 6 and was dependent on the presence of cells expressing high levels of CD45 180-kD isomer (UCHL1 monoclonal antibody), a marker for activated or memory cells, but not for CD45R (SN130 monoclonal antibody) a marker for naive or unprimed T cells. This suggests a similarity to the recall response to tuberculin antigen. These results suggest that the proliferative response to malaria antigens observed previously and described as a nonspecific mitogenic response may be a cross-reactive response to epitopes shared between P. falciparum and other common immunogens. This would explain the establishment of T cell clones to malaria antigens from such donors, but might suggest that the epitopes to which such clones are specific may be of questionable protective or diagnostic use.     

Division of human helper T cells into two sets on the basis of the induction of anti-tumor cytotoxicity by phorbol ester and calcium ionophore

Fourteen noncytotoxic human helper T cell clones were examined for autocrine proliferative responses and cytotoxicity to tumor cells after stimulation with 12-O-tetradecanoylphorbol 13-acetate (TPA) and ionomycin (Io). Although all clones responded to alloantigen, they could be divided into two groups based on their proliferative response or lack of it to TPA/Io. Nonresponders could not be converted to responder status by addition of interleukin (IL) 1 or indomethacin to the cultures. Responder status did not correlate with any of the following properties of the clones: originating donor, recognitive specificity, B cell helper activity, proliferative response to IL 2 or 4, lymphokine secretory capacity or density of expression of antigen receptors, CD4 or HLA class II molecules. Responder status did, however, correlate with the ability of TPA/Io to induce major histocompatibility complex-unrestricted cytolytic activity directed towards natural killer-resistant tumor cells. These results divide human helper cells into two types on the basis of induction of anti-tumor cytotoxicity.     

Liver-infiltrating T helper cells in autoimmune chronic active hepatitis stimulate the production of autoantibodies against the human asialoglycoprotein receptor in vitro.

Autoantibodies against the human asialoglycoprotein receptor (ASGPR) occur in the sera of patients with autoimmune liver disorders. Liver-infiltrating T cell clones that specifically recognize the ASGPR have been described in patients with autoimmune chronic active hepatitis (AI-CAH) and primary biliary cirrhosis (PBC). Recently, we have shown that peripheral blood mononuclear cells (PBMC) from patients with AI-CAH or PBC but not chronic viral hepatitis secreted anti-ASGPR antibodies in vitro. In this study we characterized the influence of liver-infiltrating T cells on the secretion of ASGPR-specific autoantibodies by autologous B cells in cell culture supernatants. T cell clones from liver biopsies of three patients with chronic autoimmune liver disorders (one with AI-CAH, two with PBC) were isolated and investigated for their proliferative response to soluble ASGPR and their helper function provided to autoantibody-secreting B lymphocytes. PBMC from these patients secreted autoantibodies spontaneously in their cell culture supernatants and showed a proliferative response to ASGPR. T cell-depleted PBMC, however, lacked spontaneous antibody secretion. Four CD4+CD8- liver-infiltrating T cell clones showed a proliferative response to ASGPR and also induced spontaneous anti-ASGPR antibody production in cell culture supernatants when added to autologous T cell depleted PBMC. Activated supernatants of these T cell clones failed to induce antibody production. None of seven CD4+CD8- and two CD4-CD8+ T cell clones non-responding to ASGPR provided this help for antibody secretion. Anti-ASGPR secretion in vitro could not be inhibited by the addition of MoAbs raised against monomorphic determinants on HLA class II molecules. The addition of purified ASGPR or polyclonal-activating pokeweed mitogen showed no influence on the production of autoantibodies in these cultures. These data show that B lymphocytes require T cell help for the production of ASGPR-specific antibodies. This help can be provided by ASGPR-responsive T helper cells via cellular interactions.     

Bee venom phospholipase A2-specific T cell clones from human allergic and non-allergic individuals: cytokine patterns change in response to the antigen concentration.

Protein antigens with both allergenic and immunoprotective properties represent appropriate molecules to study IgE and IgG regulation. We have established a panel of T cell clones specific to bee venom phospholipase A2 (PLA) from human individuals allergic, hyposensitized or immune (protected) to bee sting. All clones obtained were CD3+, CD4+ and expressed alpha, beta T cell receptor. Depending on the T cell clone, maximal stimulation required 1 to 100 micrograms/ml of PLA, and the addition of interleukin (IL)-2 and/or IL-4 increased their antigen-dependent proliferation. Following antigen stimulation, the clones produced IL-4, interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor. Most clones also produced tumor necrosis factor alpha (TNF-alpha) and tumor necrosis factor beta (TNF-beta), and some produced IL-5 and/or IL-2. Both absolute and relative amounts of secreted cytokines depended on the antigen concentration. At low antigen doses, IL-4 was produced but little or not IFN-gamma, whereas at higher PLA concentrations significant amounts of both IL-4 and IFN-gamma were obtained. Thus, these PLA-specific T cell clones could be classified according to the changes in the ratio of IL-4/IFN-gamma production in response to increasing antigen concentrations. Clones derived from allergic and hyposensitized individuals required higher critical amounts of antigen for IFN-gamma induction, and expressed increasing IL-4/IFN-gamma ratios with increasing concentrations of PLA. Modulation of cytokine patterns by the dose of the antigen may be a driving force for IgE or IgG formation resulting in allergy or immunoprotection.     

Desmoglein 3-specific T regulatory 1 cells consist of two subpopulations with differential expression of the transcription factor Foxp3

Pemphigus vulgaris (PV) is an autoimmune bullous skin disorder associated with autoantibodies against desmoglein (Dsg) 3. An imbalance of type 1 regulatory T (Tr1) cells and T helper type 2 (Th2) cells specific for Dsg3 may be critical for the loss of tolerance against Dsg3 in PV. Within the population of Dsg3-responsive, interleukin (IL)-10-secreting Tr1 cell clones, two major subpopulations were identified and sorted by fluorescence-activated cell sorting (FACS) based on their size and granularity. Upon in vitro culture, the larger subpopulation differentiated back into the two former subpopulations of the Tr1 cell clones, while the smaller subpopulation died within 2 weeks. The smaller subpopulation of the Tr1 cell clones was characterized by the expression of Foxp3, the secretion of IL-10, transforming growth factor (TGF)-beta and IL-5 upon stimulation with Dsg3, a proliferative response to IL-2 but not to Dsg3 or mitogenic stimuli, and an inhibitory effect on the proliferative response of Dsg3-responsive Th clones in a Dsg3-specific manner. In contrast, the larger subpopulation showed a Th-like phenotype, lacking Foxp3, cytotoxic T-lymphocyte antigen 4 (CTLA4) and glucocorticoid-induced tumour necrosis factor receptor (GITR) expression and IL-2 secretion, and did not mount a proliferative response to Dsg3 and mitogenic stimuli. The two Tr1 subpopulations showed expression of identical T-cell receptor (TCR) V beta chains which varied among the PV patients studied. Upon inhibition of Foxp3, the smaller Tr1 subpopulation developed a proliferate response to Dsg3 and mitogenic stimuli, no longer suppressed Dsg3-specific Th cells, lost expression of GITR and CTLA4 and secreted IL-2. Thus, our observations suggest a distinct relationship between Dsg3-specific Tr1 and Th-like cells which may be critical for the continuous generation and survival of Dsg3-specific Tr1 cells.     

Induction of antigen-specific CD8+ cytolytic T cells by the exogenous bacterial antigen streptolysin O in rhesus monkeys.

We have characterized the T cell responses induced by streptolysin O (SLO), a sulfhydryl-activated hemolysin secreted by streptococci, by applying long-term in vitro culture and cloning rhesus monkey (Macaca mulatta) T cells. T cell lines specific for SLO were obtained from three rhesus monkeys. These T cell lines required autologous antigen-presenting cells (APC) to proliferate in response to SLO and did not respond to purified protein derivative. Phenotypic analysis showed that the cells from two of three SLO-specific T cell lines were more than 85% CD3+CD4-CD8+ after prolonged in vitro culture. The rh 1842 CD8+ T cell line proliferative response to SLO was inhibited by the addition of anti-major histocompatibility complex (MHC) class I and anti-CD8 but not of anti-MHC class II and anti-CD4 monoclonal antibody (mAb). This cell line was able to lyse P815 target cells in the presence of anti-CD3 mAb and did not show natural killer activity. Moreover, specific lysis of autologous but not allogeneic non-rosetting E- cell targets pulsed with SLO was observed. Such lysis was inhibited by the addition of anti-MHC class I mAb. In the attempt to identify the restriction elements involved in SLO presentation APC from six unrelated rhesus monkeys and three humans were used. A CD4+ rh 1842 T cell clone responded when SLO was presented by one of six, and a CD8+ rh 1842 T cell clone by four of six rhesus monkeys APC. Both CD4+ and CD8+ T cell clones did not respond when SLO was presented by human APC. However, both clones responded when APC from all donors were used in conjunction with anti-CD3 mb. Furthermore, SLO required active processing to be presented to CD4+ and CD8+ T cell clones as glutaraldehyde fixation of APC before but not after antigen pulsing inhibited T cell proliferation. The SLO-specific CD8+ cytolytic T cells described here could play a role in the regulation of the immune response occurring during streptococcal infections and/or could participate in the pathogenesis of poststreptococcal nonsuppurative sequelae.     

Establishment of stable CD8+ suppressor T cell clones and the analysis of their suppressive function.

Stable CD8+ suppressor T cell (Ts) clones were established by a relatively simple method. Keyhole limpet hemocyanin (KLH)-primed spleen cells from C3H mice were depleted of B cells and CD4+ T cells by panning and cytotoxic treatment, and the resulting CD8+ T cells were periodically stimulated with antigen and irradiated syngeneic spleen cells followed by manifestation in interleukin-2 (IL-2) containing medium. T cell clones with a definite suppressor function were established by limiting dilution. They were defined as classical effector type Ts of CD8+ phenotype as they had constant and definite suppressor functions in antigen-induced T cell proliferation and specific antibody response against T cell-dependent antigens without detectable cytotoxic activity against both antigen presenting cells (APC) and helper T cells (Th). They showed no helper activity for B cells and produced no detectable helper type lymphokines such as IL-2 and IL-4. CD8+ Ts clones were able to inhibit the antigen-induced IL-2 production of normal and cloned T cells. Their suppressive activity was antigen-nonspecific and major histocompatibility complex-unrestricted. CD8+ Ts clones were also able to suppress the proliferative response of Th clones induced by immobilized anti-T cell receptor (TcR) and anti-CD3 mAbs but not the response induced by concanavalin A (ConA) and IL-2. All the CD8+ T cell clones established independently utilized the TcR V beta 8 gene. Syngeneic antigen presenting cells could induce proliferation of these CD8+ clones, which was blocked by anti-CD8 and anti-I-Ak monoclonal antibody (mAb) but not by anti-class I mAbs. The stimulation of CD8+ Ts clones with immobilized anti-CD3 resulted in the release of a suppressor factor(s) that potently inhibited the antigen-induced proliferation of CD4+ Th clones and the in vitro secondary antibody formation.     

Selective sensitization of peripheral blood T lymphocytes to hepatitis B core antigen in patients with chronic active hepatitis type B.

The proliferative response of peripheral blood T cells to hepatitis B surface antigen (HBsAg), pre-S antigen and hepatitis B core antigen (HBcAg) has been studied in 20 patients with hepatitis B virus induced chronic active hepatitis (CAH) and in 12 control subjects. Eleven of the 20 CAH patients showed a significant T lymphocyte proliferative response to HBcAg, whereas no proliferation was detectable in response to envelope antigens (HBs and pre-S) in any patient. T cell subset fractionation revealed that HBcAg specific proliferation was limited to the CD4+ (helper/inducer) population. CD8+ (suppressor/cytotoxic) T cells were unresponsive to HBcAg and did not suppress the proliferative response of autologous CD4+ cells. The HBcAg specific T cell proliferative response did not correlate with serum anti-core antibody titres or with biochemical evidence of liver disease. The present results show the selective presence of HBcAg-sensitized T cells in the peripheral blood of patients with HBsAg positive CAH and suggest that the peripheral lymphoid compartment may not reflect immunopathogenetically important cellular events operative at the site of tissue injury.     

Severe glomerular epithelial cell damage does not prevent passive Heyman nephritis in rats.

Analysis of the local cell-mediated immunity within the central nervous system is limited by the small amount of material available. In the present report we describe that T lymphocyte clones can be expanded directly from the cerebrospinal fluid (CSF) using T cell growth factor and irradiated feeder cells. Without in vitro restimulation such clones can reproducibly be generated from fresh or cryopreserved CSF lymphocytes. From a patient with tuberculous meningitis, T lymphocyte clones were obtained that showed tuberculin (PPD) specific proliferative responses restricted by a single HLA-DR antigen. One of these clones was restricted by an antigen different from the serologically defined HLA-DR since this clone recognized PPD only on autologous but not on HLA-DR matched monocytes. These experiments show that T lymphocytes involved in the in situ immune response can be cloned directly from the site of inflammation.     

Two subsets of cloned T helper cells exhibit different activation requirements and characteristics

An anti-clonotypic monoclonal antibody (mAb 211G7H) was generated against a T helper cell clone which specifically recognized type II collagen. Besides inhibiting the proliferative response of the immunizing T cell clone to type II collagen, mAb 211G7H (soluble form) also suppressed the antigen-induced proliferation of several other T cell clones which shared similar specificity for antigen and major histocompatibility complex with the immunizing T cell clone. On the other hand, mAb 211G7H did not inhibit the responses of clones exhibiting different antigenic specificities from the clonotype-positive T cell clones. It was also demonstrated that these clonotype-positive T cell clones responded differently to mAb 211G7H when it was immobilized. Based upon their proliferative responses to immobilized anti-clonotype 211G7H mAb, two subpopulations of T cell clones were defined. Collagen-specific T cell clones of the first group proliferated poorly when stimulated with immobilized anti-clonotype mAb, by contrast, T cell clones belonging to the second group proliferated well to immobilized mAb. Furthermore, upon stimulation with immobilized 211G7H mAb, the second subpopulation of cloned T cells produced both interleukin (IL) 2 and IL4, while the first group secreted IL2 but not IL4. The cloned T cells from the group which responded weakly to immobilized anti-clonotype mAb also mediated reduced proliferative responses to IL2 in the presence of immobilized 211G7H mAb. Finally, these two subsets of T cell clones were found to respond differently to other non-antigen stimuli such as IL4 and phorbol 12-myristate 13-acetate. Thus, from a panel of collagen-specific T cell helper clones which had similar receptor fine specificities, we have isolated two subsets of cloned T helper cells that displayed different activation requirements and lymphokine production.     

Lymphocyte sensitization to Aspergillus fumigatus in allergic bronchopulmonary aspergillosis.

Peripheral blood mononuclear cell (PBMC) proliferation induced by an extract of Aspergillus fumigatus (AF) was examined in patients with allergic bronchopulmonary aspergillosis (ABPA), all of whom had an immediate skin prick test reaction (SPT) and increased RAST binding to AF, and, for comparison, in individuals without immediate SPT reactivity or increased RAST binding to AF. The proliferative responses of PBMC from the ABPA patients were greater than those from the comparison donors. A substantial proportion of the comparison group, however, showed evidence of a specific immune response to AF, with AF-specific IgG measured by ELISA and specific lymphoproliferative responses. AF-responsive T cell lines and T cell clones were established from both ABPA patients and IgE-negative individuals. These clones, of helper/inducer (CD4+) phenotype, showed antigenic specificity and MHC restriction. The stimulating antigen was determined for four of six clones derived from a skin-prick-test-negative individual, and found to be of Mr 18 kD, possibly the major allergen, 'Ag 3'. ABPA patients showed a marked diminution of the proliferative response during disease exacerbation.     

Malaria specific human T cell clones: crossreactivity with various plasmodia species.

Peripheral blood mononuclear cells (PBMC) from donors with or without previous exposure to malaria in vivo were cultivated for 4 to 7 days in the presence of different malaria antigen (M.Ag) preparations: Plasmodium falciparum (P.f.Ag), P. berghei (P.b.Ag) and P. gallinaceum (P.g.Ag). All preparations induced a proliferative response in PBMC from donors with or without previous exposure to malaria. PBMC from both groups of donors were then primed with each of the three M.Ag and cloned in presence of autologous irradiated PBMC and M.Ag. All 152 clones recovered had the T4+ phenotype and required autologous antigen presenting cells (APC) in addition to M.Ag for proliferation. Species specific and crossreactive T cell clones (T cell clones proliferating in the presence of the three M.Ag preparations) were recovered following priming with each of the three M.Ag. Species specific and crossreactive T cell clones were recovered in similar percentages (approximately 50%) using PBMC from donors with or without previous exposure to malaria. These data are discussed in the context of crossreactivity at the T cell level among various plasmodia species and in relation to epitope recognition of malaria native, synthetic and fusion polypeptides.     

Prominent T lymphocyte response to Borrelia burgdorferi from peripheral blood of unexposed donors

The proliferative response of peripheral blood T cells to the spirochete, Borrelia burgdorferi, can be as pronounced in unexposed normal individuals as it is in Lyme disease patients. This finding was observed using three geographically distinct isolates of B. burgdorferi. The response is not due to a lipopolysaccharide effect of the spirochete, is sensitive to Proteinase K, and requires antigen processing. It does not result from cross-reactivity of memory T cells that may be reactive to another antigen; the proliferative response to B. burgdorferi is equally distributed between naive (CD29^?, CD45RO^?) and memory (CD29⁺, CD45RO⁺) T cells, whereas the tetanus response is confined to the memory subset. In support of this notion, cord blood specimens that contain almost entirely naive T cells, respond as vigorously to B. burgdorferi as T cells from normal adult peripheral blood. A large panel of CD4⁺ T cell clones has been derived that are specific for B. burgdorferi. The majority of these clones are reactive to B. burgdorferi in the presence only of autologous HLA-DR molecules. Collectively, these data suggest that the T cell response from normal individuals is more likely due to multiple antigenic epitopes within Borrelial proteins than a superantigen response.     

Human T cell clones with specificity for insulinoma cell antigens

Several lines of evidence suggest that islet-specific T cells are important in the pathogenesis of the insulitis resulting in insulin-dependent diabetes mellitus (IDDM). Therefore, we decided to analyze islet-specific T cell reactivity in the peripheral blood of IDDM patients. With the use of insulinoma membranes as antigen, T cell lines were generated from peripheral blood mononuclear cells of patients with recent onset of the disease. In a proliferation assay such T cell lines responded to insulinoma membranes and, though to a lesser extent, also to fibroblast membranes, the control antigen used. One of the T cell lines was cloned. Eight clones were isolated that respond to insulinoma antigens. Five of these eight clones appeared to be specific for insulinoma membranes, i.e. they demonstrated proliferation in response to insulinoma but not fibroblast membranes. These insulinoma-specific proliferative responses are HLA-DR restricted.     

Antigen presentation by interferon-γ-treated thyroid follicular cells inhibits interleukin-2 (IL-2) and supports IL-4 production by B7-dependent human T cells

The consequence of recognition of antigen on antigen-presenting cells that are induced to express major histocompatibility complex (MHC) class II molecules following an inflammatory process is still not clear. In this study, we have investigated the outcome of antigen presentation by epithelial cells and we have used as a model thyroid follicular cells (TFC) that are known to express MHC class II molecules in autoimmune thyroid diseases and acquire the capacity to present autoantigens to T cells infiltrating the thyroid gland. The result show that MHC class II-expressing TFC were unable to stimulate a primary T cell alloresponse, using CD4⁺ T cells from three HLA-mismatched responders. Phenotypic analysis showed that TFC, after incubation with interferon-γ, do not express the co-stimulatory molecules B7-1 (CD80) and -2 (CD86). Addition of murine DAP.3 cells expressing human B7-1 (DAP.3-B7) to cultures containing peripheral blood CD4⁺ T cells and DR1-expressing TFC led to a proliferative response, suggesting that the failure of TFC to stimulate a primary alloresponse was due to a lack of co-stimulation. Similarly, HLA-DR-restricted, influenza-specific T cell clones dependent on B7 for co-stimulation did not respond to peptide presented by TFC; again the lack of response could be overcome by co-culture of TFC with DAP.3-B7. Furthermore, recognition of antigen on TFC inhibited interleukin-2 (IL-2) production in the B7-dependent T cells. In contrast, in T helper type 0 (Th0) T cells, IL-4 release was not affected by TFC presentation. In addition, antigen presentation by TFC favored IL-4 production relative to IL-2 production by B7-indpendent Th0 clones. These results suggest that antigen presentation by MHC class II⁺ TFC may induce tolerance in autoreactive Th1 cells but may simultaneously favors a Th2 response in uncommitted T cells, and thereby support autoantibody production.     

Staphylococcal enterotoxin B as a potent suppressant of T lymphocytes: trace levels suppress T lymphocyte proliferative responses.

Staphylococcal enterotoxins have long been known to be powerful stimulators of T lymphocytes in mouse and man. In a previous study we showed that high concentrations of staphylococcal enterotoxin serotype B (SEB) failed to stimulate strong proliferative responses by Lewis rat T lymphocytes. Moreover, concentrations of SEB (10-50 micrograms/ml) that stimulated optimal mouse T lymphocyte proliferative responses suppressed a mitogen- or antigen-induced rat T lymphocytes proliferative responses. The present study shows that SEB at low concentrations (as low as 10(-3)-10(-4) micrograms/ml) and often also trace levels (about 10(-6)-10(-7) micrograms/ml) suppresses both rat and mouse T lymphocytes proliferative responses to mitogen or antigen. Furthermore, under different circumstances, SEB may have conflicting effects on the same T cells. While high concentrations (1-50 micrograms/ml) of SEB stimulate certain mouse T cell clones, low concentrations or trace levels have a potent suppressive effect on the same clones. The results indicate that the in vitro conflicting effects of SEB on the same T cells are concentration dependent and may reflect its in vivo effects on SEB-reactive T lymphocytes. The suppression of the mitogen- or antigen-induced stimulation of T cell clones by SEB was direct and did not require the agency of suppressor cells. Furthermore, the suppression by low amounts of SEB was not major histocompatibility complex restricted and affected a large proportion of both rat and mouse T lymphocyte subpopulation, regardless of their antigenic specificity. The concomitant suppressogenic and stimulatory characteristics of SEB support the conclusion that, under different conditions, SEB can be considered a "super-suppressogen" as well as a "super-antigen". Overall, the results suggest that SEB, and possibly other bacterial toxins, could be useful in immunomodulation of specific T cell responses.     

Clonal analysis of liver-infiltrating T cells in patients with LKM-1 antibody-positive autoimmune chronic active hepatitis

Autoantibodies against microsomal antigen of liver and kidney (LKM-1) are diagnostic markers for a subgroup of autoimmune chronic active hepatitis (AI-CAH). Cytochrome P450dbl, now classified as cytochrome P450 IID6, is the major antigen of LKM-1 antibodies. Immunohistological studies suggest that hepatic injury in AI-CAH is mediated by liver-infiltrating T cells. In the present study the specificity and function of liver-infiltrating T cells was analysed at the clonal level. Phenotypical characterization of 189 T cell clones isolated from four liver biopsies of LKM-1 antibody-positive patients showed an enrichment of CD4+ CD8- T cell clones proliferated specifically in the presence of recombinant human LKM-1 antigen (rLKM). This reaction was restricted to autologous antigen-presenting cells and to HLA class II molecules. In order to see whether rLKM was also recognized by peripheral blood T lymphocytes (PBL) we tested the proliferative response of PBL from several individuals. PBL from three of the four patients with LKM-1 antibody-positive AI-CAH proliferated to rLKM, whereas no response was seen with PBL from patients with LKM-1 antibody-negative chronic liver diseases and from healthy blood donors. These data demonstrate that the LKM-1 antigen is recognized by liver-infiltrating T cells in LKM-1 antibody-positive AI-CAH. For further functional characterization, liver-derived T cell clones were tested for their cytotoxic activity. In the presence of phytohaemagglutinin 24 out of 26 CD4- CD8+ but also 20 out of 63 CD4+ CD8- T cell clones lysed autologous as well as allogenic EBV-transformed B cell lines or K562 cells. Five CD4- CD8+ T cell clones lysed autologous but not allogenic B cell lines spontaneously in a HLA class I-restricted manner. Although the antigen specificity of these clones is still unknown the data show the presence of autoreactive T cells at the site of inflammation that could contribute in the pathogenesis of AI-CAH.