The T-cell repertoire is heavily influenced by tolerance to polymorphic self-antigens

Differential reactivity of V beta 9 T cells to minor lymphocyte stimulating antigen in vitro and in vivo

The monoclonal antibody (mAb) MR10-2 is specific for mouse T cells expressing the V beta 9 chain of T cell antigen receptor. This mAb reacts with 2% of peripheral T cells in a number of different strains of mice, but in mice expressing the minor lymphocyte stimulating (Mls)-1a antigen, V beta 9+ T cells recognized by MR10-2 are deleted. However, we failed to demonstrate the Mls-1 a antigen-specific response of naive, non-activated V beta 9 T cells in vitro. On the other hand, T cells activated initially with anti-V beta 9 (MR10-2) mAb in vitro are capable of responding to the Mls-1a antigen. These results demonstrate that Mls-1a reactivity of V beta 9 T cells depends on the activation state of the T cells, suggesting a differential activation requirement between naive, non-activated T cells and previously activated T cells.

Activation of murine T cells by staphylococcal enterotoxin E: requirement of MHC class II molecules expressed on accessory cells and identification of V beta sequence of T cell receptors in T cells reactive to the toxin

We investigated a mechanism leading to activation of murine T cells by staphylococcal enterotoxin E (SEE). L cells transfected with I-Ab genes but not control L cells supported IL-2 production by SEE-induced C57BL/6 T lymphoblasts upon restimulation with SEE. mAb to I-Ab markedly inhibited the above response. Flow cytometric analyses showed that SEE-induced C57BL/6 T lymphoblasts are composed of both CD4+ T cells and CD8+ T cells, and that larger parts of them bore V beta 11 (40-75%). mAb to V beta 11 markedly inhibited the SEE-induced proliferative response and IL-2 production by T cells. Analysis of SEE-induced IL-2 production in spleen cells from various mouse strains showed that C57BL/6 and B10.A(4R) mice (I-E, not expressed; V beta 11+ T cells, normally generated) are highly responsive to SEE. In contrast, BALB/c, C3H/HeN, (C57BL/6 x BALB/c or C3H/HeN) F1 mice (I-E, normally expressed and V beta 11+ T cells, deleted), and SJL and C57L mice (V beta 11 genes, deleted) are weakly responsive to SEE. The results indicate that SEE activates mainly T cells bearing V beta 11 in physical association with MHC class II molecules expressed on AC. In addition, the results indicate that SEE activates both CD4+ T cells and CD8+ T cells.

A potential role for microbial superantigens in the pathogenesis of systemic autoimmune disease

We have attempted herein to demonstrate how microbial superantigens could promote an abnormal form of "cognate" T helper-B cell interaction, analogous to that which may occur during GVH disease, leading to B cell activation and systemic autoimmunity. In vitro studies performed at our laboratory and others have demonstrated that resting human B cells bind microbial superantigens and present them to superantigen-reactive autologous T helper cells, resulting in T cell activation and polyclonal IgM and IgG production by the superantigen-bearing B cells. In vitro studies of microbial superantigen-mediated murine T helper-B cell interactions demonstrate preferential help for B cells that have encountered specific antigen. Both in humans and in mice, the cellular interactions involved and the B cell responses induced are highly analogous to those mediated by allospecific T helper-B cell interaction. Finally, the results of studies carried out on T cell-deficient (nude) mice suggest that microbial superantigens may trigger similar T helper cell-dependent polyclonal IgM and IgG responses in vivo. These mice will be studied over time and tested for the development of autoantibodies characteristic of SLE and of autoimmune organ system damage, the occurrence of which are predicted by our model.

Genomically imposed and somatically modified human thymocyte V beta gene repertoires

The effect of thymic selection on the expressed human T-cell antigen receptor beta-chain variable region (V beta) gene repertoire was examined by using a multiprobe RNase protection assay. The relative abundance of transcripts for 22 V beta genes (encompassing 17 of the 20 human V beta gene subfamilies) within a thymus, and among 17 thymuses, was variable. On the basis of the presence of corresponding mRNAs, no genomic deletions were detected, but several coding region polymorphisms were identified. Analysis of mature T-cell subsets revealed the absence of complete "superantigen"-mediated V beta deletions, suggesting that this phenomenon, in contrast to mouse, is uncommon or absent in humans. However, several V beta genes were over- or underexpressed in one or both mature single-positive (CD4+8- or CD8+4-) thymocyte subsets compared to syngeneic total, mostly immature thymocytes. Whether these changes are induced by relatively weak superantigens or conventional antigens and whether the downshifts are caused by negative selection or lack of positive selection remains to be determined.

Clonal deletion of V beta 14-bearing T cells in mice transgenic for mammary tumour virus

Autoreactive T lymphocytes are clonally deleted during maturation in the thymus. Deletion of T cells expressing particular receptor V beta elements is controlled by poorly defined autosomal dominant genes. A gene has now been identified by expression of transgenes in mice which causes deletion of V beta 14+ T cells. The gene lies in the open reading frame of the long terminal repeat of the mouse mammary tumour virus.

Self-reactive T cells are activated by the 65-kDa mycobacterial heat-shock protein in neonatally thymectomized mice

To elucidate the mechanism of autoimmune disease in neonatally thymectomized (NTX) mice, we have investigated the responsiveness of the self-reactive T cells which have not undergone clonal deletion in such animals. Consistent with a recent report (Yuuki et al., Eur. J. Immunol. 1990. 20: 1475), T cells bearing V beta 11-gene products capable of recognizing I-E-encoded molecules were readily detected in the mature T cell pool of NTX BALB/c (I-Ed, Mls-2a) mice. The V beta 11-bearing T cells in NTX mice expressed interleukin 2 receptors and responded normally to signals delivered through the T cell receptor. Notably, these T cells in NTX mice proliferated significantly after culture with the 65-kDa mycobacterial heat-shock protein, whose amino acid sequence is highly homologous to that in eukaryotes. These results suggest that self-reactive T cells in NTX mice may be activated by heat-shock proteins derived from various pathogens and/or stressed autologous cells, resulting in the development of autoimmune diseases in such animals.

Requirement of dendritic cells and B cells in the clonal deletion of Mls-reactive T cells in the thymus

The present study was performed to identify cells responsible for the elimination of T cells reactive with minor lymphocyte-stimulating (Mls) antigens during T cell development. Experiments were carried out in a fetal thymus organ culture (FTOC) system. To examine the tolerance-inducing activity, various populations of cells from adult CBA/J (Mls-1a) mice were injected into deoxyguanosine (dGuo)-treated FTOC of C3H/He (Mls-1b) mice with a microinjector, and 2 d later, the thymus lobes were injected with fetal thymus cells from C3H/He mice as T cell precursors. After 14 d of cultivation, cells were harvested and assayed for the expression of the T cell receptor V beta 6 element. The absence or marked reduction of T cells expressing V beta 6 at high levels (V beta 6high) was regarded as indicating the deletion of Mls-1a-reactive T cells. T cell-depleted populations of thymic as well as splenic cells from CBA/J mice were able to induce clonal deletion. Further characterization of the effector cells was carried out by fractionating the spleen cells before injecting them into dGuo-FTOC. None of the dish-adherent population, dish-nonadherent population, or purified B cells alone were able to induce clonal deletion, whereas the addition of purified B cells to adherent cells restored tolerance inducibility. It was further shown that a combination of CBA/J B cells and C3H/He dendritic cells was effective in eliminating Mls-reactive clones. These results indicate that for the deletion of clones reactive with Mls antigens during T cell development in the thymus, both DC and B cells are required.

Cell and receptor requirements for streptococcal pyrogenic exotoxin T-cell mitogenicity

Streptococcal pyrogenic exotoxins (SPEs) A, B, and C, like other members of the pyrogenic toxin family, are able to cause toxic shock-like syndromes. One of the major properties of these toxins is the ability to induce T-cell proliferation. Characterization of T cell mitogenicity associated with SPEs A, B, and C was undertaken. SPEs A, B, and C were mitogenic for C57BL10/SnJ and BALB/cWAT T cells, with activities differing in intensity depending on the mouse strain and toxin employed. SPE-induced, T-cell-proliferative activity was dependent on class II major histocompatibility complex molecules expressed on antigen-presenting cells. The abilities of SPEs A, B, and C to preferentially stimulate murine cells with certain T-cell receptor V beta s were investigated by fluorescence-activated cell sorter analysis. SPE A preferentially activated T cells expressing V beta 8 but not V beta 3, 6, or 11, while SPEs B and C preferentially stimulated T cells which did not express any of the tested V beta s.

Staphylococcal enterotoxin B as a potent suppressant of T cell proliferative responses in rats

The staphylococcal toxins are well known as stimulators of powerful T lymphocyte proliferative responses. Staphylococcal enterotoxin B (SEB) was found, in both humans and mice, to preferentially stimulate T cells bearing particular V beta gene products as part of their functional T cell receptor alpha/beta. In contrast to this reported stimulatory activity we demonstrate here that SEB is a poor stimulant of T lymphocyte proliferative responses in Lewis rats. Moreover, under appropriate conditions, SEB can serve as a powerful suppressant of Lewis rat T lymphocytes, capable of abolishing their antigen-specific or mitogen-stimulated proliferative responses. Suppression of mitogen-induced proliferative responses of rat T cell clones was effective in the presence of syngeneic or allogeneic accessory cells and similar to its stimulatory characteristics, SEB suppressed high proportions of rat T lymphocyte subsets. These data suggest that in certain circumstances SEB can be considered a "supersuppressogen" as well as a "superantigen". Whether SEB will be "superantigen" or "supersuppressogen" is likely to depend on the TcR elements of the lymphocytes as well as on the MHC molecules presenting SEB.

Genes encoding ligands for deletion of V beta 11 T cells cosegregate with mammary tumour virus genomes

The T-cell receptor (TCR) repertoire is selected in the thymus after rearrangement of genes encoding TCR alpha and beta chains. Selection is based on the recognition by newly emergent T cells of self-ligands associated with molecules of the major histocompatibility complex: some combinations result in positive selection, others in negative selection. Negative selection, or clonal deletion, is an important mechanism for eliminating autoreactive T cells. A group of self-ligands involved in clonal deletion was identified because they, like exogenous superantigens, were recognized by almost all T cells expressing particular TCR V beta genes. V beta 17a T cells are deleted by a tissue-specific ligand; V beta 6, V beta 7, V beta 8.1 and V beta 9 T cells are deleted by the minor lymphocyte-stimulating (Mls) determinant Mls-1a; V beta 3 T cells by Mls-2a and Mls-3a; V beta 11 T cells by ligands encoded by independently segregating genes; and V beta 5 T cells by ligands encoded by two genes. Chromosome mapping using recombinant inbred strains of mice and classic backcrosses show that Mls-1a in DBA/2 mice is encoded on chromosome 1, that one of the two ligand genes for deletion of V beta 5 T cells maps to chromosome 12 and that a ligand gene for V beta 11 deletion is linked to the CD8 locus on chromosome 6. Here we present evidence from three sets of backcross mice for concordance between V beta 11 deletion ligand genes on chromosomes 6, 12 and 14 and endogenous mouse mammary tumour virus integrant (Mtv) genomes.(ABSTRACT TRUNCATED AT 250 WORDS)

An endogenous retrovirus mediating deletion of alpha beta T cells?

A special class of self-antigens (endogenous superantigens) is capable of deleting many murine T cells on the basis of their expression of particular T-cell receptor V beta gene segments. In mice that endogenously express these antigens, tolerance is mediated in part by the clonal deletion of the relevant V beta-bearing T cells. The deletion of I-E-reactive V beta 5.2-bearing T cells is dependent on the coexpression of an I-E tolerogenic coligand (Etc)14 and the gene for one of these coligands, Etc-1, maps to chromosome 12, near the mouse mammary tumour viral integrant, Mtv-9. Here we report a perfect genetic linkage between Etc-1 and Mtv-9 and show that Etc-1 is also involved in the I-E-dependent deletion of T cells bearing V beta 5.1 and V beta 11 domains. We also demonstrate that Mtv-9 transcripts are present in B cells expressing Etc-1 and suggest that the coligand recognized by roughly 15% of all T lymphocytes is encoded by the Mtv-9 genome.

Linkage of Mls genes to endogenous mammary tumour viruses of inbred mice

T cells that recognize self antigen are clonally deleted in the thymus--a maturation process that occurs in the context of histocompatibility molecules and the T-cell receptor. The minor lymphocyte stimulation antigens (Mls) effect these deletions through interactions with the V beta portion of the T-cell receptor, thus mimicking bacterial 'superantigens'. Intrigued by the fact that each known Mls gene maps to the same chromosomal region as an endogenous mouse mammary tumour virus (Mtv), we reevaluated the linkage relationships between the two gene families. Here we report perfect concordance in inbred and recombinant inbred mice between the presence of four Mtv proviruses with the expression of Mls gene products. These data suggest a general model in which mammary tumour virus gene products themselves are the ligands that shape a considerable portion of the immunological repertoire of common laboratory mice.

Role of MHC and antigens in T-cell development

The role of self-peptides in influencing the development of the T-cell repertoire has been the focus of recent studies. The findings suggest that the recognition of self-peptides bound to MHC proteins in the thymus is part of the thymic self-recognition process that results in selective maturation, or positive selection of T cells.

Towards an integrated view of thymopoiesis

One prediction from the complex series of steps in intrathymic T-cell differentiation is that to regulate it the stroma controlling the process must be equally complex: the attraction of precursors, commitment to the T-cell lineage, induction of T-cell receptor (TCR) gene rearrangement, accessory molecule expression, repertoire expansion, major histocompatibility complex (MHC) molecule-based selection (positive and negative), acquisition of functional maturity and migratory capacity must all be controlled. In this review, Richard Boyd and Patrice Hugo combine knowledge of T-cell differentiation with thymic stromal cell heterogeneity to offer an integrated view of thymopoiesis within the thymic microenvironment.

Restricted expression of T cell receptor V beta but not V alpha genes in rheumatoid arthritis

Synovial fluids of patients with rheumatoid arthritis contain activated T lymphocytes that may play an important role in the pathogenesis of the disease. Previous studies have suggested that the T cell receptor (TcR) repertoire of these cells is restricted, reflecting in vivo selection of a limited number of T cell specificities at the site of inflammation. To characterize better these T cell populations we used the polymerase chain reaction technology to estimate the proportion of TcR alpha and beta RNA containing any particular V elements from transcripts directly isolated from the synovial fluid cells and from peripheral blood mononuclear cells of three patients with rheumatoid arthritis. Our data show that, in contrast to peripheral blood mononuclear cells, synovial fluid T cells expressed only few V beta transcripts, one of which was overrepresented in two patients. Peripheral and joint fluid T cells, on the other hand, appeared to express the same set of non-restricted V alpha elements. These results suggest that a major antigen associated with the pathogenesis of rheumatoid arthritis may interact selectively with the V beta component of the TcR.

Programmed cell death and extrathymic reduction of Vbeta8+ CD4+ T cells in mice tolerant to Staphylococcus aureus enterotoxin B

Clonal deletion and functional inactivation of self-reactive cells have been invoked as mechanisms underlying intrathymic development of T-cell tolerance. The relative importance of these mechanisms in the development of tolerance of more mature, peripheral T cells either to self or to exogenous antigens is unclear, although recent data relate the development of T-cell tolerance in the periphery to clonal anergy. We have now investigated the induction of extrathymic tolerance using BALB/c mice that were made tolerant to Staphylococcus aureus enterotoxin B, a superantigen which specifically interacts in such mice with T cells bearing V beta 8 antigen receptors. Both euthymic and athymic mice made tolerant to S. aureus enterotoxin B had a markedly reduced number of V beta 8.1,2+ CD4+ peripheral T cells. This reduction was accompanied by genomic DNA fragmentation that is associated with cell death. These results indicate that a deletional mechanism can contribute to the induction of T-cell tolerance in peripheral lymphoid cells.

Direct binding of secreted T-cell receptor beta chain to superantigen associated with class II major histocompatibility complex protein

The interaction of the T-cell receptor (TCR) with peptide antigen plus major histocompatibility complex (MHC) protein requires both alpha and beta chains of the TCR. The "superantigens" are a group of molecules that are recognized in association with MHC class II but that do not appear to conform to this pattern. Superantigens are defined as such because they cause the activation or thymic deletion of many or all T cells bearing specific TCR beta-chain variable region (V beta) elements. The strong association of particular V beta S with T-cell responses to superantigens suggests that their interaction with the TCR is fundamentally different from that of most antigens. We have directly investigated the involvement of the beta chain in recognition of a superantigen by using a secreted, truncated TCR beta chain and the bacterial superantigen staphylococcal enterotoxin A complexed to cell-surface MHC class II. We demonstrate that this interaction is specific for the enterotoxin and is dependent on MHC class II expression by the cell. The reaction can be inhibited by antibodies against the three components of the reaction: V beta, enterotoxin, and class II. This shows that the TCR beta chain is sufficient to mediate the interaction with a superantigen-class II complex. The TCR alpha chain and co-receptors such as CD4 are not required.

Antigenic mimicry and autoimmune diseases

The finding of cross-reactive autoantibodies or sequence homology does not necessarily mean that this molecular mimicry is biologically meaningful or associated with disease pathogenesis. For example, relatives of persons with putative autoimmune insulin-dependent diabetes [123], and elderly humans [124] have a high incidence of autoantibodies which are generally not associated with autoimmune disease. In addition, natural antibodies to cell constituents [125] may be present in normal sera. These antibodies need to be directed against biologically important domains of host cell proteins in order to mediate autoimmune disease [27]. In spite of extensive homology between two sequences, a cross-reactive immune response may not be generated. The dissimilar amino acids should not be radical substitutions or affect the binding properties of the molecule. For instance, antibodies to synthetic peptides with only one substitution in a 19 amino acid sequence may not bind the whole protein [126]. Despite an identical six amino acid sequence shared by HLA-B27 and an EBV protein, no cross-reactive antibodies to EBV peptides were found in HLA-B27 positive patients with AS or RS. Unless the homology and subsequent crossreactive immune response can recognize a host protein intimately involved in disease pathogenesis, autoimmune disease is unlikely to occur.

Defect in negative selection in lpr donor-derived T cells differentiating in non-lpr host thymus

Transplantation of bone marrow cells of lpr/lpr mice into irradiated normal mice fails to develop massive lymphadenopathy or autoimmunity but causes severe graft-vs.-host-like syndrome. To elucidate an abnormality of lpr/lpr bone marrow-derived T cells, we transplanted bone marrow cells of Mlsb lpr/lpr mice into H-2-compatible Mlsa non-lpr mice. Although lpr/lpr T cell precursors repopulated the host thymus as well as +/+ cells, a proportion of CD4+CD8+ cells decreased, and that of both CD4- and CD8- single-positive cells increased compared with those of +/+ recipients. Notably, in MRL/lpr----AKR and C3H/lpr----AKR chimeras, CD4 single-positive thymocytes contained an increased number of V beta 6+ cells in spite of potentially deleting alleles of Mlsa, whereas V beta 6+ mature T cells were deleted in the MRL/+ ----AKR and C3H/+ ----AKR chimeras. There was no difference between MRL/+ ----AKR and MRL/lpr----AKR chimeras in their proportion of V beta 3+ cells because both host and donor strain lack the deleting alleles. Interleukin 2 receptor expression of mature T cells, in the thymus and lymph node, was obviously higher in the MRL/lpr----AKR chimeras, in particular in the "forbidden" V beta 6+ subset. Moreover, lpr donor-derived peripheral T cells showed vigorous anti-CD3 response. These results indicate that lpr-derived T cells escape not only tolerance-related clonal deletion but also some induction of unresponsiveness in the non-lpr thymus.

Extrathymic tolerance of mature T cells: clonal elimination as a consequence of immunity

The mechanism by which T lymphocytes are tolerized to self or foreign antigens is still controversial. Clonal deletion is the major mechanism of tolerance for immature thymocytes; for mature T cells, tolerance is considered to reflect anergy rather than deletion, and to be a consequence of defective presentation of antigen. This paper documents a novel form of tolerance resulting when mature T cells encounter antigen in immunogenic form. Evidence is presented that exposure of mature T cells to Mlsa antigens in vivo leads to specific tolerance and disappearance of Mlsa-reactive V beta 6+ T cells. Surprisingly, the clonal elimination of V beta 6+ cells is preceded by marked expansion of these cells. Thus, tolerance induction can be the end result of a powerful immune response. These data raise important questions concerning the relationship of tolerance and memory.

Expression of the human V beta 8 gene product preferentially correlates with class II major histocompatibility complex restriction specificity

We report that, in peripheral blood T cells, the V beta 8 gene product is much more represented on CD4+CD8- than on CD4-CD8+ lymphocytes. This skewing was observed in all individuals tested and with two independent strategies, one of which allows the selection of V beta 8+ T cells independently from their major histocompatibility complex-antigen specificity. Our data imply that the human V beta 8 gene product confers class II restriction specificity and that both the T cell receptor chains and CD4 molecule are involved in the selection of the T cell repertoire.

V beta 17 gene polymorphism in wild-derived mouse strains: two amino acid substitutions in the V beta 17 region greatly alter T cell receptor specificity

Of 41 wild-derived mouse strains analyzed, 14 contained T cells bearing V beta 17 receptors in spite of the concomitant expression of I-E antigens. Reciprocal F1 and F2 hybrids of one of these strains, PWK, with laboratory strains revealed different patterns of V beta 17 T cell deletions from those observed with V beta 17 T cells from SJL, implying that the two V beta 17 regions are associated with recognition of distinct superantigens. The structures of the V beta 17 alleles differ by two amino acid substitutions, which lie together in an area distant from the predicted site of T cell receptor interaction with peptide-MHC complexes but overlapping with that implicated in V beta 8.2 recognition of Mls-1 superantigen. This demonstrates that the self-superantigen leading to V beta 17 T cell deletion varies with the allele of the receptor gene and confirms that T cell deletions by such ligands involve interactions with a region of the V beta domain that is distinct from the conventional combining site.

Failure of clonal deletion in neonatally thymectomized mice: tolerance is preserved through clonal anergy

Self-tolerance is achieved in part through intrathymic deletion of self-reactive T cells. The necessity of the thymus for this process is suggested by the development of autoimmune diseases in neonatally thymectomized (neoTx) mice and by the failure of clonal deletion in nude mice. Indeed, the present study demonstrates that neonatal thymectomy on day 3 after birth results in the failure of clonal deletion of V beta 11+ T cells in BALB/c mice and V beta 5+ and V beta 6+ T cells in DBA/2 mice. However, these potentially autoreactive cells are nonfunctional as measured by proliferation and lymphokine production after stimulation with appropriate anti-V beta mAbs or stimulator cells. It appears that this induction of nonresponsiveness may have occurred extrathymically: the early neonatal thymus (presumably the source of the peripheral T cells observed in neoTx mice) also contains T cells with self-reactive receptors, but these cells are fully functional. Therefore, neonatal thymectomy aborts deletion of self-reactive T cells, but self-tolerance is maintained through functional inactivation of potentially self-reactive clones.

Expression of CD4 can confer major histocompatibility complex class II-associated superantigen reactivity upon a T cell receptor derived from a CD8-dependent cytotoxic T lymphocyte clone

It has been shown that reactivity against major histocompatibility complex (MHC) class II-associated Mlsa determinants is mainly mediated by CD4+ V beta 6+ T cells. 3F9 is a CD8+ CTL clone which is specific for the alloantigen H-2Db. While 3F9 is V beta 6+, it is not Mlsa reactive, presumably because it does not express CD4. 3F9 utilizes the same T cell receptor (TcR) V alpha V beta combination as LB2, a CD4+ T helper clone specific for chicken red blood cells (cRBC)/I-Ab and yet differs from LB2 in the junctional sequences in both TcR chains. CD4+ CD8- and CD4-CD8- hybridomas expressing the 3F9 TcR were tested for reactivity against Mlsa and cRBC/I-Ab. Only the CD4+CD8- hybridomas were Mlsa reactive, and antibody inhibition studies revealed that this reactivity was both CD4 and MHC class II dependent. Therefore the expression of the CD4 molecule can make an MHC class I-restricted TcR Mlsa reactive. Neither type of hybridoma reacted against cRBC, thus the main difference in the antigen reactivity between 3F9 and LB2 lies in the TcR junctional regions.

Inhibition of the mixed lymphocyte reaction by T cell vaccination

Immunization with attenuated activated autoreactive T cell lines and clones induces a response in syngeneic animals which can induce protection or recovery from autoimmune disease. This process has been termed T cell vaccination. The aim of the present study was to investigate the effect of immunization with MHC-reactive T cells on the mixed lymphocyte reaction (MLR). By injecting attenuated activated T cells primed for an alloantigen, we markedly reduced the MLR in both rats and mice. This depression appeared to be mediated by active suppression; lymphoid cells from T cell-vaccinated animals suppressed the MLR responsiveness of T cells from naive animals. Suppression of the MLR was not restricted to the major histocompatibility complex (MHC) alleles used to prime the animals from which the T cell vaccines were prepared; the MLR to other MHC allelic stimulator cells was also suppressed. This MHC-unrestricted suppression could not be attributed to an anti-ergotypic response to non-MHC-linked activation markers on T cells; an anti-ergotypic response augmented rather than suppressed the MLR. We herein propose that T cell vaccination might influence the MLR by suppressing the responses of diverse T cells which bear shared T cell receptor idiotypes.

Distinct fates of self-specific T cells developing in irradiation bone marrow chimeras: clonal deletion, clonal anergy, or in vitro responsiveness to self-Mls-1a controlled by hemopoietic cells in the thymus

Elimination of potentially self-reactive T lymphocytes during their maturation in the thymus has been shown to be a major mechanism in accomplishing self-tolerance. Previous reports demonstrated that clonal deletion of self-Mls-1a-specific V beta 6+ T lymphocyte is controlled by a radiosensitive I-E+ thymic component. Irradiation chimeras reconstituted with I-E- bone marrow showed substantial numbers of mature V beta 6+ T cells despite host Mls-1a expression. Analysis of the functional properties of such chimeric T cells revealed a surprising variability in their in vitro reactivity to host Mls-1a, depending on the H-2 haplotype of stem cells used for reconstitution. In chimeras reconstituted with B10.S (H-2s) stem cells, mature V beta 6+ lymphocytes were present but functionally anergic to host-type Mls-1a in vitro. In contrast, in chimeras reconstituted with B10.G (H-2q) bone marrow, nondeleted V beta 6+ cells were highly responsive to Mls-1a in vitro. These findings suggest that clonal anergy of V beta 6+ cells to self-Mls-1a may be controlled by the affinity/avidity of T cell receptor interactions with bone marrow-derived cells in the thymus depending on the major histocompatibility complex class II molecules involved. Furthermore, chimeras bearing host (Mls-1a)-reactive V beta 6+ cells did not differ clinically from those with anergic or deleted V beta 6+ cells and survived more than one year without signs of autoimmune disease. Interestingly, their spleen cells had no Mls-1a stimulatory capacity in vitro. Therefore, regulation at the level of antigen presentation may be an alternative mechanism for maintenance of tolerance to certain self-antigens such as Mls-1a.

Determinants of the B-cell response against a transgenic autoantigen

The failure to induce self-tolerance of simian virus 40 large tumor antigen (T antigen) expressed in the pancreatic beta cells of transgenic mice results in an autoimmune response against this protein and the cells that synthesize it. In every transgenic mouse with delayed onset of T-antigen expression and consequent nontolerance, B cells, T cells, and macrophages are attracted to and infiltrate the pancreatic islets. In contrast, the incidence, onset, and intensity of the B-cell response to produce anti-T-antigen autoantibodies vary considerably with genetic background. Thus the initial attraction of lymphocytes to the cells synthesizing a non-self antigen can be separated from the activation of a B-cell response against it. Haplotypes of the major histocompatibility complex (MHC) differentially influence the character of the autoimmune response, with H-2d and H-2k conferring a high incidence of humoral autoimmunity. Additional non-MHC linked genes are also implicated in control of the B-cell response.

Selective anergy of V beta 8+,CD4+ T cells in Staphylococcus enterotoxin B-primed mice

The cellular basis of the in vitro and in vivo T cell responses to Staphylococcus enterotoxin B (SEB) has been investigated. The proliferation and cytotoxicity of V beta 8.1,2+,CD4+ and CD8+ T cells were observed in in vitro response to SEB. In primary cytotoxicity assays, CD4+ T cells from control spleens were more active than their CD8+ counterparts, however, in cells derived from SEB-primed mice, CD8+ T cells were dominant in SEB-specific cytotoxicity. In vivo priming with SEB abrogated the response of V beta 8.1,2+,CD4+ T cells despite the fact that these cells exist in significant number. This SEB-specific anergy occurred only in V beta 8.1,2+,CD4+ T cells but not in CD8+ T cells. These findings indicate that the requirement for the induction of antigen-specific anergy is different between CD4+ and CD8+ T cells in post-thymic tolerance, and the existence of coanergic signals for the induction of T cell anergy is suggested.

In vivo induction of anergy in peripheral V beta 8+ T cells by staphylococcal enterotoxin B

We have developed a model of peripheral in vivo T cell tolerance that is induced by administration of the protein superantigen staphylococcal enterotoxin B (SEB). Rather than activating V beta 8+ T cells, in vivo administration of SEB induced in them a profound state of anergy. This was shown by their failure to proliferate to subsequent in vitro restimulation with SEB or to anti-V beta 8 antibodies. This unresponsiveness was V beta 8 specific since T cells from SEB-immunized mice responded normally to other antigens. 8 d after SEB administration, there was no reduction in the number of V beta 8+ T cells or in the intensity of V beta 8 T cell receptor (TCR) expression. Although a portion of the V beta 8+ T cells from SEB-primed mice were able to express interleukin 2 receptors (IL-2Rs), they failed to proliferate in response to exogenous IL-2, indicating they were defective in their IL-2 responsiveness. 2-4 wk after SEB administration, there was a reduction of approximately 50% in the number of V beta 8+ cells in immunized compared with control animals. There was, however, no reduction in the level of TCR expression on the remaining V beta 8+ cells. These data demonstrate that proteins that activate T cells in vitro in a V beta-specific manner can induce a state of anergy in peripheral T cells in vivo and may possibly further mediate clonal deletion in a portion of the tolerized cells.

Participation of a dominant cytotoxic T cell population defined by a monoclonal antibody in syngeneic anti-tumor responses

Cytotoxic T lymphocyte (CTL) clones against a syngeneic Friend virus-induced erythroleukemia (FBL-3) were generated in C57BL/6 (B6) mice. A monoclonal antibody (mAb, N9-127) was then raised from spleen cells of a B6 mouse immunized syngenically against one of these CTL clones. This mAb detected the epitope (127Ep) of the T cell antigen receptor (TcR) on the immunizing CTL clone in tests of immunoprecipitation, specific blocking and proliferation, and induction of TcR-mediated nonspecific lysis of the clone. In addition, more than 10% of the FBL-3-specific CTL clones isolated independently from B6 mice were 127Ep+. Further investigations revealed that up to 30% of B6 anti-FBL-3 T cell blasts from mixed lymphocyte tumor cell cultures were positive for this epitope, and that its expression was confined to CD8+ T cells. This epitope was not detected in naive lymphoid cells from the spleen, lymph nodes or thymus or in T cell clones specific for tumors other than FBL-3. The FBL-3-specific CTL clones were next grouped into 127Ep+ and 127Ep- clones. Sequence analyses of the CTL clone used for immunization showed the rearrangements of V alpha 1J alpha 112-2 and V beta 10D beta 2.1J beta 2.7. Southern blot analysis of all the 127Ep+ CTL clones examined showed the same DNA rearrangement bands of both the TcR alpha and beta genes. These findings suggested that mAb N9-127 recognized the shared determinant of the TcR molecule which was expressed by the dominant CTL population in the response to FBL-3.

The requirement of intrathymic mixed chimerism and clonal deletion for a long-lasting skin allograft tolerance in cyclophosphamide-induced tolerance

Mechanisms of cyclophosphamide (CY)-induced tolerance were studied. When C3H/He Slc (C3H; H-2k, Mls-1b) mice were primed i.v. with 1 x 10(8) viable spleen cells from H-2-identical AKR/J Sea (AKR; H-2k, Mls-1a) mice and treated with 200 mg/kg of CY 2 days later, a long-lasting skin allograft tolerance to AKR was established. When [C57BL/6 Sea (B6; H-2b, Mls-1b) x AKR]F1 (B6AKF1) cells were used as the tolerogen, however, only a moderate, but not long-lasting, skin tolerance to AKR was observed. In the C3H mice treated with AKR cells and CY, the intrathymic clonal deletion of V beta 6+ T cells, which are strongly correlated with reactivity to Mls-1a antigens, was observed in the chimeric thymus on day 35, although neither the clonal deletion of V beta 6-bearing T cells nor the mixed chimerism was observed in the thymus on day 14. In the C3H mice treated with B6AFKF1 cells followed by CY, however, neither the clonal deletion of V beta 6+ T cells nor the mixed chimerism was observed in the thymus throughout the test period. In the lymph nodes of the C3H mice treated with AKR cells and CY, only CD4+ V beta 6+ T cells, bur not CD8+V beta 6+ T cells, had selectively decreased by day 14, and they were hardly detectable on day 35. The selective decrease of CD4+V beta 6+ T cells in the lymph nodes was also observed by day 14 when B6AKF1 cells were used as the tolerogen, although CD4+V beta 6+ T cells gradually increased on day 35, at which time almost all skin grafts from AKR had already been rejected. These results strongly support the necessity of the intrathymic mixed chimerism and clonal deletion of donor-reactive T cells for a long-lasting skin allograft tolerance in CY-induced tolerance.

HLA-DR alleles differ in their ability to present staphylococcal enterotoxins to T cells

Staphylococcal enterotoxins (SEs) have been shown to bind to major histocompatibility complex (MHC) class II proteins and stimulate T cells in a V beta-specific manner, and these V beta specificities for various SEs have been well documented in mice and humans. This study was undertaken in order to examine the ability of human class II molecules to present SEs to human and murine T cell hybridomas. Using a panel of transfectants expressing individual HLA class II antigens, we have shown that HLA-DR alleles differ in their ability to bind and present SEs. Since the HLA-DR proteins share a common alpha chain, these results indicate that the polymorphic beta chain plays an important role in SE binding and presentation to T cells. In addition, we have shown that human class II isotypes markedly differ in their ability to present SEs. The results of this study should provide information on the region of MHC class II molecules that interacts with foreign, and perhaps self, super-antigens.

Expression of T cell antigen receptor heterodimers in a lipid-linked form

The interaction of the T cell receptor for antigen (TCR) with its antigen-major histocompatibility complex ligand is difficult to study because both are cell surface multimers. The TCR consists of two chains (alpha and beta) that are complexed to the five or more nonpolymorphic CD3 polypeptides. A soluble form of the TCR was engineered by replacing the carboxyl termini of alpha and beta with signal sequences from lipid-linked proteins, making them susceptible to enzymatic cleavage. In this manner, TCR heterodimers can be expressed independently of the CD3 polypeptides and in significant quantities (0.5 milligram per week). This technique seems generalizable to biochemical and structural studies of many other cell surface molecules as well.

Residues of the variable region of the T-cell-receptor beta-chain that interact with S. aureus toxin superantigens

The alpha beta T-cell antigen receptor (TCR) recognizes antigenic peptides in the context of self major histocompatibility complex (MHC) molecules. The specificity of recognition of MHC plus antigen is generally determined by a combination of the variable elements of alpha- and beta-chains of the TCR. Several types of antigen, however, have been identified that, when bound to MHC molecules, stimulate T cells bearing particular variable-region beta-chain (V beta) elements irrespective of the other variable components of the TCR. These have been termed 'superantigens', and here we are concerned with one type of superantigen, the toxins produced by Staphylococcus aureus. T cells have been found that bear closely related members of the same V beta family but respond differently to S. aureus toxins; in particular, cells bearing the human V beta 13.2 element respond to toxin SEC2, whereas cells bearing human V beta 13.1 do not. We have now defined the residues of the V beta element responsible for this difference, and find that they reside in a region thought to lie on the side of the TCR molecule, away from the conventional antigen/MHC-binding site. The evolutionary conservation of this site may be due to its having an important role in some function of the TCR other than the binding of conventional antigen plus MHC.

MHC-linked protection from diabetes dissociated from clonal deletion of T cells

The I-E molecule of the major histocompatibility complex (MHC) can prevent the spontaneous development of diabetes in nonobese diabetic (NOD) mice. The mechanism of this protection has been investigated by breeding wild-type and promoter-mutated E kappa alpha transgenes onto the NOD genetic background. Animals carrying the various mutated transgenes expressed I-E on different subsets of immunocompetent cells, and thus cells important for the I-E protective effect could be identified. Although the wild-type transgene prevented the infiltration of lymphocytes into pancreatic islets, none of the mutants did. However, all of the transgenes could mediate the intrathymic elimination of T cells bearing antigen receptors with variable regions that recognize I-E. Thus, the I-E molecule does not protect NOD mice from diabetes simply by inducing the deletion of self-reactive T cells.

T cell receptor V beta genes expressed by IgG anti-DNA autoantibody-inducing T cells in lupus nephritis: forbidden receptors and double-negative T cells

In the (SWR x NZB)F1 (SNF1) model of lupus nephritis, pathogenic variety of IgG anti-DNA autoantibodies are induced by certain T helper (Th) cells that are either CD4+ or CD4-CD8- (double negative; DN) in phenotype. From the spleens of eight SNF1 mice with lupus nephritis, 149 T cell lines were derived and out of these only 25 lines (approximately 17%) were capable of augmenting the production of pathogenic anti-DNA autoantibodies. Herein, we analyzed the T cell receptor (TcR) V beta genes used by 16 such pathogenic autoantibody-inducing Th cell lines. Twelve of the Th lines were CD4+ and among these five lines expressed V beta 8 (8.2 or 8.3). The V beta 8 gene family is contributed by the NZB parent to the SNF1 mice, since it is absent in the SWR parental strain. Three other CD4+ Th lines expressed V beta 4, another was V beta 2+ and one line with poor autoantibody-inducing capability expressed V beta 1. Four autoantibody-inducing Th lines from the SNF1 mice had a DN phenotype and these lines were also autoreactive, proliferating in response to syngeneic spleen cells. Among these DN Th lines, two expressed V beta 6 and one expressed V beta 8.1 TcR. Both of these are forbidden TcR directed against Mls-1a (Mlsa) autoantigens expressed by the SNF1 mice and such autoreactive T cells should have been deleted during thymic ontogeny. Thus, the DN Th cells of non-lpr SNF1 mice are different from the DN cells or MRL-lpr which lack helper activity and do not express forbidden TcR. The spleens of 6 out of 19 nephritic SNF1 animals tested also showed an expansion of forbidden autoreactive TcR+ cells that were mainly DN. Two of these animals expressed high levels of V beta 6 (anti-Mlsa) and V beta 11 (anti-I-E) TcR+ cells, three others had high levels of V beta 11+ cells alone and one animal had an expanded population of V beta 17a+ (anti-I-E) cells. The I-E-reactive TcR again should have been eliminated in the SNF1 thymus, since they express I-E molecules contributed by the NZB parent. The SWR parents of SNF1, are I-E-; moreover, they lack the V beta 11 gene but they express V beta 17a in peripheral T cells. Whereas the NZB parents are I-E+, they lack a functional V beta 17a gene and they delete mature V beta 11+ T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular analysis of the influences of positive selection, tolerance induction, and antigen presentation on the T cell receptor repertoire

Immunization of both B10.A and B10.S(9R) mice with pigeon cytochrome c (pcc) elicits T cells capable of proliferating to pcc presented on I-E major histocompatibility complex (MHC) molecules. The T cell receptor (TCR) repertoire used by pcc-specific T cells from these two strains is markedly different, even for T cells recognizing very similar antigen/MHC complexes. Our current studies have been directed toward explaining this differential expression between MHC congenic strains of TCR gene elements capable of recognizing similar ligands. Analysis of the TCR repertoire of pcc-specific T cells from F1[B10.A x B10.S (9R)]----parent radiation chimeras has demonstrated that much of this difference is a result of the positive selection of T cells for MHC restriction specificity. Further analysis of T cell lines from F1 mice and from radiation chimeras stimulated in vitro with pcc on both B10.A and B10.S(9R) antigen-presenting cells has provided clear-cut examples of the influence of positive selection, tolerance induction and of both in vivo and in vitro antigen presentation on the shaping of the TCR repertoire for a protein antigen. This is the first molecular analysis of how positive selection, tolerance induction, and antigen presentation can combine to mold the TCR repertoire.

Clonal anergy in self-reactive alpha/beta T cells is abrogated by heat-shock protein-reactive gamma/delta T cells in aged athymic nude mice

Although T cells proliferate and differentiate primarily in the thymus, athymic nude mice contain an appreciable level of T cell receptor alpha/beta and gamma/delta T cells, suggesting the existence of the extrathymic pathway in the development of both T cells. Recent studies with nude mice indicate that clonal deletion of self-reactive T cells does not occur extrathymically. In the present study, we have investigated the responsiveness of self-reactive T cells differentiating along an extrathymic pathway in aged BALB/c (H-2d, Mls-1b2a, I-E+, 7-8 month old) nude mice. Consistent with recent reports, T cells bearing V beta 3 or V beta 11, which are important for recognizing proteins encoded by the Mls-2a or the I-E allele, respectively, are readily detected in age nude mice. The V beta 3- or V beta 11-bearing T cells, however, do not proliferate in response to staphylococcal enterotoxin A which specifically stimulates V beta 3- or V beta 11-bearing T cells. When exogenous recombinant interleukin 2 was added to the culture, the V beta 3-bearing T cells in aged nude mice significantly proliferated in response to staphylococcal enterotoxin A. Aged nude mice also contained a substantial level of gamma/delta T cells which account for 15.6% of all Thy-1.2+ cells. The gamma/delta T cells proliferated and produced a significant level of interleukin 2 in response to the 65-kDa mycobacterial heat-shock protein, which is highly homologous to its eukaryotic counterpart. These results suggest that unresponsiveness of self-reactive T cells may be reversed by T cells responding to stress proteins expressed by the invading microbes and/or the stressed autologous cells.

Induction of neonatal tolerance to Mlsa antigens by CD8+ T cells

Antigen-specific tolerance of T cells to minor lymphocyte stimulatory (Mls) antigens can be induced in mice by neonatal injection of foreign lymphohematopoietic cells. Although immune responses to Mlsa antigens are controlled by B cells, CD8+ T cells were the most effective cell type for induction of Mlsa tolerance. Tolerance was evident in both thymus and lymph nodes and could be induced by as few as 2 x 10(4) CD8+ T cells; these cells were 50 to 100 times as potent as CD4+ cells or B cells in causing functional tolerance and deletion of V beta 6+ T cells. Thus, intrathymic contact with antigens expressed on CD8+ T cells may play an important role in controlling the normal development of tolerance.

Identification of the region of T cell receptor beta chain that interacts with the self-superantigen MIs-1a

Superantigen-MHC complexes are known to stimulate T cells primarily via the V beta element of the T cell receptor. In this paper we identify a number of amino acid residues that define the region of a particular V beta element interacting with one of the self-superantigens, MIs-1a. These residues are predicted to lie on a beta-pleated sheet of the T cell receptor, away from the complementarity determining regions of the receptor, which are thought to interact with complexes of conventional peptide antigens and MHC. In support of this prediction, mutations affecting MIs-1a activity have no effect on the response to conventional antigen and MHC.

T cell reactivity to MHC molecules: immunity versus tolerance

The specificity of mature CD8+ and CD4+ T lymphocytes is controlled by major histocompatibility complex (MHC) class I and class II molecules, respectively. The MHC class specificity of T cells is stringent in many assays, but is less evident when cells are supplemented with exogenous lymphokines. The repertoire of T cells is shaped through contact with MHC molecules in the thymus and involves a complex process of positive selection and negative selection (tolerance). Tolerance of immature T cells to MHC molecules can reflect either clonal deletion or anergy and results from intrathymic contact with several cell types, including epithelial cells and cells with antigen-presenting function. Unlike immature T cells, mature T cells are relatively resistant to tolerance induction. In certain situations partial unresponsiveness of mature T cells can be achieved by exposing T cells to foreign MHC molecules expressed on atypical antigen-presenting cells. Tolerance is rarely complete, however, and the precise requirements for tolerizing mature T cells are still unclear.