The antigen-specific, major histocompatibility complex-restricted receptor on T cells. VI. An antibody to a receptor allotype

In vivo preferential usage of TCR V beta 8 in Torpedo acetylcholine receptor immune response in the murine experimental model of myasthenia gravis

The aim of our study was to determine the T cell receptor (TCR) V beta gene usage involved in the T cell response to Torpedo AChR in C57BL/6 mice. The specific proliferation towards AChR was found to be blocked by anti-V beta 8.1,2,3 and to a lesser extent by anti-V beta 5 mAbs, but not by the other antibodies used (anti-V beta 2, V beta 6, V beta 9). In addition, a significant expansion of CD4+ V beta 8+ cells was observed when lymph node cells from these primed mice were stimulated in vitro with purified AChR. Involvement of V beta 8 subfamilies was also explored in vivo. After 7 days of treatment, there was a striking inhibition of the proliferative response of cells from anti-V beta 8.1,2,3-treated mice and a moderate inhibition when using anti-V beta 8.1,2 and anti-V beta 8.2 antibodies. Thus our in vitro and in vivo analysis indicate that in C57Bl/6 mice, T cell response to AChR is restricted to few V beta TCR, mostly belonging to the V beta 8 sub-families.

Immunological function of a defined T-cell population tolerized to low-affinity self antigens

In the thymus there are two major mechanisms of T-lymphocyte tolerance: clonal deletion and clonal inactivation. One important problem underlying the mechanism of clonal inactivation is why unresponsive cells are maintained in the mature peripheral T-cell repertoire. Here we report that transgenic alpha beta T-cells may be tolerized to a self antigen Mls-1a, but still retain proliferative responses for alternative peptide antigens and superantigens. These self-tolerant T cells can also provide immunopathological and memory cytotoxic function in vivo. We propose that high-affinity/avidity self-reactive T cells are deleted in the thymus, whereas lower-affinity/avidity interactions lead to unresponsiveness and define the 'resting threshold' for a given T cell. These low-affinity self-tolerant T cells remain functionally competent for high-affinity foreign antigens, and efficiently eliminate natural pathogens in vivo.

T cell receptor V beta repertoire in mice lacking endogenous mouse mammary tumor provirus

When endogenous mouse mammary tumor virus (MMTV) superantigens (SAg) are expressed in the first weeks of life an efficient thymic deletion of T cells expressing MMTV SAg-reactive T cell receptor (TcR) V beta segments is observed. As most inbred mouse strains and wild mice contain integrated MMTV DNA, knowing the precise extent of MMTV influence on T cell development is required in order to study T cell immunobiology in the mouse. In this report, backcross breeding between BALB.D2 (Mtv-6, -7, -8 and -9) and 38CH (Mtv-) mice was carried out to obtain animals either lacking endogenous MMTV or containing a single MMTV locus, i.e. Mtv-6, -7, -8 or -9. The TcR V beta chain (TcR V beta) usage in these mice was analyzed using monoclonal antibodies specific for TcR V beta 2, V beta 3, V beta 4, V beta 5, V beta 6, V beta 7, V beta 8, V beta 11, V beta 12 and V beta 14 segments. Both Mtv-8+ mice and Mtv-9+ mice deleted TcR V beta 5+ and V beta 11+ T cells. Moreover, we also observed the deletion of TcR V beta 12+ cells by Mtv-8 and Mtv-9 products. Mtv-6+ and Mtv-7+ animals deleted TcR V beta 3+ and V beta 5+ cells, and TcR V beta 6+, V beta 7+ and V beta 8.1+ cells, respectively. Unexpectedly, TcR V beta 8.2+ cells were also deleted in some backcross mice expressing Mtv-7. TcR V beta 8.2 reactivity to Mtv-7 was shown to be brought by the 38CH strain and to result from an amino acid substitution (Asn-->Asp) in position 19 on the TcR V beta 8.2 fragment. Reactivities of BALB.D2 TcR V beta 8.2 and 38CH TcR V beta 8.2 to the exogenous infectious viruses, MMTV(SW) and MMTV(SHN), were compared. Finally, the observation of increased frequencies of TcR V beta 2+, V beta 4+ and V beta 8+ CD4+ T cell subsets in Mtv-8+ and Mtv-9+ mice, and TcR V beta 4+ CD4+ T cells in Mtv-6+ and Mtv-7+ mice, when compared with the T cell repertoire of Mtv- mice, is consistent with the possibility that MMTV products contribute to positive selection of T cells.

Cross-reactive trinitrophenylated peptides as antigens for class II major histocompatibility complex-restricted T cells and inducers of contact sensitivity in mice. Limited T cell receptor repertoire

The induction of contact sensitivity in mice by hapten reagents such as trinitrochlorobenzene (TNCB) involves the activation of class II major histocompatibility complex (MHC)-restricted, hapten-specific, CD4+ T cells. Reports from different laboratories have indicated that the relevant antigenic epitopes in such reactions might include hapten-conjugated, MHC class II-associated peptides. This study for the first time directly demonstrates that hapten-peptides account for the majority of determinants recognized by trinitrophenyl (TNP)-specific CD4+ T lymphocytes. The sequences of those TNP carrier peptides do not have to be related to mouse proteins. Thus, we show that TNP-modified peptides derived from mouse IgG, pigeon cytochrome c or staphylococcal nuclease known to bind to I-Ab or from lambda repressor with specificity to I-Ad as well as TNP-proteins such as bovine serum albumin, ovalbumin or keyhole limpet hemocyanin all create class II-restricted hapten determinants for a number of TNP-specific T cell clones and hybridomas. All of these cells were induced with cells modified by trinitrobenzene sulfonic acid (TNBS). In addition, we present arguments indicating that individual TNP-specific helper T cells may cross-react with different TNP-peptides bound to identical class II molecules. Chemical treatment of antigen-presenting cells with TNCB or TNBS may thus result in a limited number of particularly repetitive immunodominant hapten epitopes. Immunodominant epitopes were also indicated by an overrepresentation of the TCR elements V beta 2 and V alpha 10 in I-Ab/TNP-specific T cells. Most importantly, however, we demonstrate that TNP attached to lysine 97 in the staphylococcal nuclease peptide 93-105 (i.e. a clearly "non-self" sequence) is able to prime mice for subsequent elicitation of contact sensitivity by TNCB in the absence of foreign protein. We take this to indicate that those TNP-peptide determinants defined by us as immuno-dominant are responsible for the induction of contact sensitivity to haptens.

Characterization of T cell receptor repertoire and anti-Ro/SSA autoantibodies in relation to sialadenitis of NOD mice

Non-obese diabetic (NOD) mice develop sialadenitis which morphologically resembles the exocrinopathy in human Sjögren's syndrome (SS). The sialadenitis is characterized by focal infiltrates of inflammatory cells. Immunoenzyme staining (ABC-technique) and monoclonal antibodies defining CD4, CD8, CD11b, TCR alpha/beta, gamma/delta, V beta 2, V beta 4, V beta 6, V beta 7, V beta 8.1, 2, V beta 10b and V beta 11 were used to examine the infiltrating mononuclear cells (MNC) in salivary glands of NOD mice. TCR alpha beta + cells dominated clearly over TCR gamma delta + cells in the salivary glands. A predominance of CD4+ T-cells was identified, while a small population of CD8+ cells was found in the salivary gland infiltrates. CD11b+ mononuclear cells were sporadically seen within the salivary gland lesions. All different TCR V beta:s which were analysed appeared to be utilized at the site of MNC infiltration in salivary glands; although with various frequencies. The frequency pattern of V beta gene expression in salivary glands was V beta 8.1,2 (15%) > V beta 6 (12%) > V beta 4 (11%) > V beta 10b (5%) > V beta 11 (5%) = V beta 2 (5%) > V beta 7 (3%). Analysis of the TCR V beta utilization in corresponding lymph nodes revealed a quite similar frequency pattern as found in the salivary glands. Serum samples were also tested for anti-Ro52, Ro60 and anti-La antibodies with Western blot. Autoantibody production was limited to anti-Ro/SSA and 3/37 (8%) of the mice were found to produce anti-Ro52 kD antibodies. The degree of sialadenitis (focus score) appeared not to influence reactivity to the Ro52 kD protein.

Deletion of CD4+ T cells and thymocytes by apoptosis in mouse mammary tumor virus (C4)-infected V beta 2 transgenic mice

Mouse mammary tumor virus MMTV (C4) encodes a V beta 2-specific superantigen. In V beta 2 transgenic (TG2) mice more than 98% of peripheral T cells express V beta 2. Infection of Tg2 mice with MMTV (C4) at birth through their mothers' milk or at 6-8 weeks of age by intravenous injection resulted in massive deletion of peripheral CD4+ T cells and suppressed thymopoiesis. The number of peripheral CD8+ T cells was not affected in neonatally infected mice. In older mice injected with MMTV (C4), splenic CD8+ T cells were significantly elevated. Suppressed thymopoiesis was observed in both neonatally infected and older mice injected with MMTV (C4). Thymocytes which expressed high level CD3 or V beta 2 were deleted. To determine if T cells or thymocytes were deleted through apoptosis, DNA fragmentation was examined by flow cytometry and diphenylamine (DPA) binding assay. Approximately 31% of CD4+ T cells from MMTV (C4)-infected Tg2 mice as compared to 6% from normal Tg2 mice contained fragmented nuclear DNA by flow-cytometric analysis. The DPA binding assay showed significantly increased total soluble DNA in lymph node cells and thymocytes from MMTV (C4)-infected mice. The kinetics of T cell and thymocyte apoptosis correspond to their deletion, supporting apoptosis as the mechanism of T cell and thymocyte deletion. CD4+ T cell and thymocyte deletion by MMTV (C4) in Tg2 mice provides a sensitive system for the analysis of retrovirus superantigen-induced apoptosis.

Transfer of Sjögren's syndrome-like autoimmune lesions into SCID mice and prevention of lesions by anti-CD4 and anti-T cell receptor antibody treatment

We describe the successful transfer of murine Sjögren's syndrome-like autoimmune lesions from MRL/lpr mice (H-2k) to severe combined immunodeficiency (SCID) mice (H-2d) and prevention of lesions by anti-CD4 and -T cell receptor V beta 8 antibody treatment. Mononuclear cells (1 x 10(6)) isolated from the inflamed submandibular salivary gland tissues of MRL/lpr mice were transferred intraperitoneally into SCID mice. Autoimmune lesions resembling those seen in Sjögren's syndrome developed in the salivary and lacrimal glands of SCID mice 8 weeks after the injection, whereas other organs did not show any lesion. This pathology resembles Sjögren's syndrome in humans involving both the salivary and lacrimal glands. Immunohistochemically, a major proportion of these infiltrating cells in transferred SCID mice were CD4+ and V beta 8+. When the spleen cells from MRL/lpr mice were injected, severe inflammatory lesions, probably resulting from a graft-versus host reaction, were observed in multiple organs of SCID mice. The disease could not be induced by intraperitoneal administration of the sera from MRL/lpr mice, or of the spleen cells from C3H/He (H-2k) and BALB/c (H-2d) mice. We detected autoantibody production specific for the salivary gland tissue in sera from transferred SCID mice. Moreover, we found that the lesions were prevented by administration of the isolated cells treated in vitro with anti-CD4 and anti-V beta 8 monoclonal antibodies. These results suggest that CD4- and V beta 8-bearing T cells are involved in recognizing an autopeptide and triggering autoimmunity in the salivary and lacrimal glands, and therapies designed with anti-CD4 and anti-V beta 8 antibodies may prove effective in treating the murine autoimmune disease.

CD4+V beta 8+ T cells mediate herpes stromal keratitis

T lymphocytes are critical in mediating herpes simplex stromal keratitis (HSK). Using immunohistologic methods, we studied the T cell subsets and the T cell receptor variable region (TCR V beta) repertoire of T cells in the eye after corneal infection with HSV (KOS strain). We investigated the possibility that there might be differential V beta preferential usage in HSK resistant and susceptible BALB/c congenic mice that differ only in a small region associated with the Igh-1 gene locus. The inflamed corneas of HSK susceptible C.AL-20 mice were mainly infiltrated by CD4+ cells and by V beta 8 expressing cells. Such T cells were not seen in the corneas of resistant C.B-17 mice. Our results indicate that CD4+V beta 8+ cells are involved in mediating HSV-1 stromal keratitis.

Mouse mammary tumor virus superantigens and murine autoimmune gastritis

BACKGROUND/AIMS

Neonatal thymectomy induces autoimmune gastritis in BALB/c (minor lymphocyte-stimulating antigen [Mls]-1b) mice, whereas DBA/2 (Mls-1a) mice are resistant. Resistance has been linked to the Mls-1a locus, which encodes a retroviral superantigen, and to superantigen reactive T cells that express V beta 6+ T-cell receptors. V beta 6+ T cells are known to be deleted in mice expressing Mls-1a superantigens.

METHODS

Neonatal thymectomized BALB/c and Mls-1a congenic BALB.D2.Mls-1a mice were analyzed to examine directly the role of Mls-1a self-superantigens and V beta 6+ T cells in autoimmune gastritis.

RESULTS

Autoimmune gastritis was detected in thymectomized BALB.D2.Mls-1a mice with high incidence. Autoantibodies to the gastric H+,K(+)-adenosine triphosphatase were present independent of the Mls phenotype in sera of gastritic mice. Severe gastritis had already appeared 1 month after thymectomy in BALB.D2.Mls-1a mice. V beta 6+ T cells were deleted in the stomach lymph nodes of 1-month-old gastritic BALB.D2.Mls-1a mice but could be detected by immunocytochemistry in the stomach lesions.

CONCLUSIONS

Endogenous Mls-1a self-superantigens and Mls-1a reactive V beta 6+ T cells are not involved in resistance to autoimmune gastritis in BALB.D2 mice.

Isolation of IgG antibody Fv-DNA from various mouse and rat hybridoma cell lines using the polymerase chain reaction with a simple set of primers

To facilitate the isolation of IgG antibody Fv-DNA sequences from hybridoma cell lines, we have established a polymerase chain reaction (PCR) procedure requiring only a small number of primers. The sense primers homologous to DNA coding for the first framework sequences were designed to hybridize to all the known antibody sequences under conditions that permit a high number of mismatches. The antisense primers were homologous to DNA coding for the beginning of the constant regions of the gamma and kappa chains. Restriction sites introduced by the primers enable the DNA to be cloned into bacterial expression vectors. Only three sense VH primers and two sense VL primers paired with one backward primer for the heavy and light chains, respectively, were necessary for the amplification of Fv-DNA from a total of 17 rodent cell lines that we have so far worked with. These consisted of 12 mouse cell lines and five rat cell lines. This procedure will therefore probably be sufficient to isolate the Fv-DNA from most mouse cell lines and possibly also from most rat cell lines.

Binding of a soluble alpha beta T-cell receptor to superantigen/major histocompatibility complex ligands

The genes for the alpha and beta chains of a murine T-cell receptor were truncated just prior to the portions encoding the transmembrane regions and introduced into baculovirus by recombination. Insect cells infected with the virus secreted a soluble form of the receptor that could be purified to homogeneity. This soluble receptor reacted with a set of six monoclonal antibodies originally raised to different epitopes on the natural transmembrane-region-containing receptor and bound with appropriate specificity to a cell surface complex of the human major histocompatibility complex class II molecule DR1 with the bacterial superantigen staphylococcal enterotoxin B.

Collagen-induced arthritis in T cell receptor V beta congenic B10.Q mice

B10.Q (H-2q) mice congenic for the truncated T cell receptor (TCR) V beta a and V beta c haplotypes were derived to examine the influence of TCR V beta genomic deletions in murine collagen-induced arthritis (CIA). Previous studies using gene complementation and segregation analyses suggested that in SWR (H-2q) mice, possession of the V beta a gene deletion results in CIA resistance. However, other studies have suggested alternative hypotheses. Thus, analysis of TCR V beta congenic mice allows for direct examination of V beta genotypes in CIA control. After immunization with bovine type II collagen, B10.Q-V beta a mice showed no difference in arthritis susceptibility, onset, or severity when compared with prototype B10.Q mice. In contrast, B10.Q-V beta c mice, which lack the V beta 6, 15, 17, and 19 families in addition to the V beta a deletion, were highly resistant to CIA. In vivo depletion of V beta 6+ T cells in B10.Q-V beta a mice significantly delayed arthritis onset suggesting that, among those V beta genes present in V beta a but absent in V beta c, V beta 6+ T cells contribute to arthritogenesis. Our findings show that, in B10.Q-V beta congenic mice, while the V beta a genotype does not prevent CIA, the highly truncated V beta c genotype renders B10.Q mice resistant to CIA. Thus, deletions within the V beta TCR genome can indeed influence CIA and suggests that the TCR repertoire displays only marginal flexibility in response to arthritogenic stimuli.

Pathogenesis of Sjögren's syndrome-like autoimmune lesions in MRL/lpr mice

Sjögren's syndrome in humans is a chronic inflammatory disease with a presumed autoimmune etiology of the exocrine organs, involving in particular the salivary and lacrimal glands. The pathogenesis of this syndrome remains unclear, but the majority of infiltrating cells in the salivary glands are CD4+ T cells both in humans and rodents. Since many cytokines are involved in the development of T cell-mediated autoimmunity, local cytokine gene expression was analyzed in vivo using an animal model for Sjögren's syndrome in MRL/lpr mice. Overexpression of interleukin-1 (IL-1)beta and tumour necrosis factor (TNF) was detected before the onset of inflammatory lesions in the salivary gland, and the upregulation of IL-6 mRNA was also found in accordance with autoimmune sialadenitis in MRL/lpr mice. The inflammatory cytokines such as IL-1 beta, TNF, and IL-6 have proved to play important roles as regulatory proteins inducing autoimmune phenomena. In addition, the expression of T cell antigen receptor beta (TCR) beta transcripts in the salivary gland tissues was analyzed. Transcript for V beta 8 was predominantly detected in the T cells infiltrating sialadenitis from the onset of the disease, suggesting that CD4+ T cells bearing TCR V beta 8 play an essential role in recognizing unknown autopeptide in the autoimmune sialadenitis of MRL/lpr mice. Furthermore, Sjögren's syndrome-like autoimmune lesions were successfully transferred into severe combined immunodeficiency (SCID) mice, and these lesions were prevented by administration of anti-CD4, and anti-V beta 8 monoclonal antibodies. This article will review recent observations of these pathogenetic analyses of autoimmune sialadenitis as it occurs in MRL/lpr mice.

New infectious mammary tumor virus superantigen with V beta-specificity identical to staphylococcal enterotoxin B (SEB)

Only few infectious mouse mammary tumor viruses (MMTV) have been characterized which induce a potent superantigen response in vivo. Here we describe the characterization of an MMTV which was isolated from milk of the highly mammary tumor-prone SHN mouse strain. Exposure of newborn mice to milk-borne MMTV (SHN) results in a very slow deletion of V beta 7, 8.1, 8.2 and 8.3 expressing peripheral T cells. Subcutaneous injection of adult mice with this virus induces a rapid and strong stimulation of all four affected V beta-subsets in vivo. Besides the strong T cell effect we observed an early proliferation and activation of the local B cell pool leading to the initial secretion of IgM followed by preferential secretion of IgG2a by day 6. Sequence comparison of the polymorphic C terminus with known open reading frames revealed high homology to the endogenous provirus Mtv-RCS. This is the first report of a virus having a complete overlap in V beta-specificity with a bacterial superantigen stimulating as many as 35% of the whole CD4+ T cell repertoire including V beta 8.2.

Sequence restrictions in T cell receptor beta-chains that have specificity for a self-peptide/Ld complex

Cytotoxic T lymphocytes that react with a complex of Ld and a ubiquitous self-peptide derived from the enzyme alpha-ketoglutarate dehydrogenase (p2Ca, LSPFPFDL) can be readily elicited by the addition of synthetic peptide to cultures of BALB/c spleen cells. As with other Ld-restricted CTL, the p2Ca-specific cells use predominantly the V beta 8.3 region. In addition, the p2Ca-specific cells use almost exclusively one of three J beta gene segments. Selection for these J beta regions appears to be related to the presence of a glutamic acid residue that is encoded at the 5' end of the J beta and is present within the CDR3. As p2Ca does not contain a complementary charged residue, this finding may suggest that the beta-chain CDR3 from p2Ca-specific CTL contacts one of the five basic residues located on the Ld helices. Together, the results support the possibility that CDR1 and/or CDR2 (within V beta 8.3) and the CDR3 may each contact the Ld molecule. In contrast to the V beta and J beta regions, the V beta D beta J beta junctions and V alpha J alpha repertoires were diverse. The diversity could explain why p2Ca-specific CTL have relatively high precursor frequencies allowing them to be generated rapidly in primary cultures.

Lack of association of V beta 8+ T cells with lupus-like syndrome in MRL-lpr/lpr mice

To evaluate the role of V beta 8+ T cells in the development of lupus-like autoimmune syndrome in MRL-lpr/lpr mice, we treated them with the F23.1 anti-V beta 8 monoclonal antibody (mAb) from birth to 4 months of age. Here we report that almost complete depletion of V beta 8+ T cells by the F23.1 mAb treatment neither inhibited nor delayed the development of hypergammaglobulinemia, autoantibody production and autoimmune glomerulonephritis in MRL-lpr/lpr mice. In addition, the F23.1 mAb treatment did not prevent the development of lymphadenopathy and the generation of a CD4-CD8- double-negative T cell subset, characteristically accumulating in lpr lymph nodes. Our results strongly argue against the idea that the V beta 8+ T cells play a critical role in the development of lupus-like autoimmune syndrome in MRL-lpr/lpr mice.

A V beta 8.2-specific superantigen from exogenous mouse mammary tumor virus carried by FM mice

A number of endogenous mouse mammary tumor virus (MMTV) proviruses encode superantigen that have the ability to stimulate T cells with a certain T cell receptor (TCR) beta-chain variable region (V beta) and to mediate the V beta-specific clonal deletion. The tumorigenic milk-borne MMTV carried by C3H and GR mice also have superantigenic properties in vivo. In the present study we identified and characterized a novel V beta 8.2-specific superantigen of exogenous MMTV carried by FM mice. The open reading frame (ORF) in the 3' long terminal repeat of the MMTV was cloned by polymerase chain reaction with primers corresponding to conserved regions spanning the ORF coding region. Sequence analysis of the ORF revealed that there is no sequence identical to those in other known MMTV in the carboxy terminus implicated in TCR V beta recognition. Subcutaneous injection of the virus into adult BALB/c mice induced an approximately three- to fourfold enlargement of draining lymph nodes and a substantial increase of V beta 8.2+ CD4+ T cells in the lymph nodes within 6 days. The exposure of newborn BALB/c mice to the virus by foster nursing resulted in a marked deletion of V beta 8.2+ cells both in CD4+ and CD8+ T cells. Thus, a novel milk-borne MMTV in FM mice expresses strong superantigenic properties capable of stimulating V beta 8.2+ T cells. V beta 8.2+ T cells have been demonstrated to be frequently involved in recognition of conventional antigens and responsible for autoimmune diseases such as experimental allergic encephalomyelitis. Therefore, the MMTV (FM) may provide a new mouse model system for inducing immunodeficiency or autoimmune disease by retroviral infection.

An analysis of sequence variation in the beta chain framework and complementarity determining regions of an allo-reactive T cell receptor

Current models of T cell receptor (TCR) structure are generally based on the homology observed between the TCR and the immunoglobulins. Furthermore, these models have predicted the locations of framework and complementarity determining regions within the alpha- and beta-chain variable regions. In order to test the validity of these models, we have generated a series of mutations within the V beta domain of an allo-reactive TCR and determined their effect on antigen recognition.

Anergic B cells constitutively present self antigen: enhanced immunoglobulin receptor-mediated presentation of antigenic determinants by B cells is hierarchical

Presentation of hen egg lysozyme (HEL) by HEL-specific B cells was studied in transgenic mice expressing anti-HEL immunoglobulin (Ig-transgenic). In T hybridoma assays, presentation of the HEL46-61 determinant by B cells from Ig-transgenic mice required 10(3)-10(4)-fold lower concentrations of HEL than were required for presentation by B cells from non-transgenic mice. In contrast, presentation of the HEL determinants 112-129 and 25-43 by HEL-specific B cells was either not significantly enhanced, or enhanced only 10-fold compared with B cells from non-transgenic mice. Enhanced presentation of HEL determinants by B cells from Ig-transgenic donors was specific for HEL, since keyhole limpet hemocyanin or synthetic HEL46-61 peptide were presented comparably by B cells from Ig-transgenic mice and non-transgenic littermates. A minimum of 1-4% Ig-transgenic B cells was required to detect enhanced presentation of HEL46-61 in vitro. Constitutive presentation of the HEL46-61 determinant, but not the HEL25-43 or HEL112-129 determinants, was detectable on anergic HEL-specific B cells from double (HEL/Ig)-transgenic mice. In the presence of exogenously added HEL, anergic B cells presented all three HEL determinants. Constitutively presented HEL46-61 was not due to endogenous synthesis of HEL antigen by anergic B cells from double-transgenic mice, as comparable levels of the HEL46-61 determinant were constitutively presented by B cells from Ig-Tg-->HEL-Tg irradiation bone marrow chimeric mice. Firstly, these results indicate that the enhanced antigen presentation mediated by Ig receptors on B cells is not equivalent for all antigenic determinants. Secondly, the data demonstrate that anergic, autoreactive B cells efficiently process and present nominal antigens in addition to constitutively presenting specific self antigen in vivo.

Clonal expansion of T lymphocytes causes arthritis and mortality in mice infected with toxic shock syndrome toxin-1-producing staphylococci

Erosive arthritis is a common and feared complication of staphylococcal infection. The reason(s) for the progressive course of the arthritis is unknown. It has been recently established that enterotoxins produced by Staphylococcus aureus display superantigen properties leading to stimulation of T cells carrying distinct T cell receptor V beta elements. This finding provides a potential connection between staphylococcal exoproteins and endogenous immune mechanisms participating in the infectious process. We have recently describe successful induction of infections arthritis in mice after intravenous inoculation of a toxic shock syndrome toxin-1 (TSST-1)-producing S. aureus LS-1 strain. Using this model we have now found a clonal expansion of T cells expressing V beta 11+ T cell receptor in the synovial tissue of arthritic mice. The role of TSST-1 as a superantigen inducing oligoclonal expansion was confirmed in an in vitro culture system. The expansion of V beta 11+ T cells proved to be of arthritogenic significance since mice genomically deleted of the V beta 11+ T cells did not develop arthritis and since pretreatment of healthy mice with anti-CD4 or anti-V beta 11 monoclonal antibodies inhibited arthritis. In addition, CD4+ and V beta 11+ T cells showed themselves to be of pathogenic significance in staphylococcal-induced mortality, since mice depleted of such populations showed increased survival. We propose that in hematogenously spread S. aureus-induced arthritis the TSST-1-dependent clonal expansion of CD4+ V beta 11+ T cells is a driving pathogenic force.

Oligoclonality of T cells in salivary glands of autoimmune MRL/lpr mice

The aim of this study was to obtain further information about exocrine glandular immunopathology and the potential of the MRL/lpr strain as a model of Sjögren's syndrome. Immunoenzyme staining (ABC technique) and monoclonal antibodies defining CD3 T-cell receptor (TcR) alpha beta, gamma delta and TcR V beta 2, V beta 4, V beta 6, V beta 7, V beta 8.1,2, V beta 10b and V beta 11 were used to identify the mononuclear cells (MNC) in salivary gland infiltrates and lymph nodes of 2- and 4-5-month-old female MRL/lpr mice. TcR alpha beta + cells dominated clearly over TcR gamma delta + cells in both salivary glands and lymph nodes. In addition, to be expressed on lymphocyte-like cells, TcR gamma delta + cells also had a dendritic appearance. The frequency pattern of TcR expression in early inflammation (2 months) was V beta 8.1, 2 > V beta 6 > V beta 4 > V beta 10b > V beta 2 > V beta 7 > V beta 11. Clear differences in frequencies could be found between salivary glands and lymph nodes in established sialadenitis (4-5 months). Particularly V beta 4, V beta 8.1,2 and V beta 10b showed expansion in salivary glands at > or = 4 months. In conclusion, this study shows a diverse repertoire of TcR at local sites of MNC infiltration in autoimmune MRL/lpr mice. However, with increasing age it also shows a preferential utilization of certain V beta gene products.

Bimodal distribution of V beta 2+CD4+ T cells in human peripheral blood

The distribution of T cells using the V beta 2 gene was studied in a group of 99 humans. The distribution of V beta 2+CD4+ levels was bimodal. Twelve individuals had levels of V beta 2+CD4+ less than 2% and 86 others had values greater than 5%. Only one individual had a value between 2% and 5%. The V beta 2 low (mean 1.3 +/- 0.49) and V beta 2 high (mean 8.2 +/- 1.65) phenotypes were stable. The V beta 2 low phenotype is inherited and not limited to HLA or T cell receptor V beta gene complexes. The CD8V beta 2 levels of CD4V beta 2 low individuals are also low. The residual V beta 2+ T cells in V beta 2 low individuals were not anergic to V beta 2-specific stimulation. These data are compatible with the effects of an endogenous superantigen.

Positive and negative thymocyte selection induced by different concentrations of a single peptide

T lymphocyte maturation is dependent on interactions between the T cell receptor (TCR) expressed on the developing thymocyte and intrathymic major histocompatibility complex (MHC)-peptide ligands. The relation between the peptide-MHC complex that results in negative or positive selection has not been identified. Here, the requirements for the maturation of thymocytes expressing a defined transgenic TCR specific for a viral peptide are studied in fetal thymic organ culture. Low concentrations of the viral peptide antigen recognized by this transgenic TCR can mediate positive selection, whereas high concentrations result in thymocyte tolerance. These findings support the affinity-avidity model of thymocyte selection.

Characterization of mouse hepatitis virus-specific cytotoxic T cells derived from the central nervous system of mice infected with the JHM strain

The cytotoxic T lymphocyte (CTL) activity of spleen cells from BALB/c (H-2d) mice immunized with the neurotropic JHM strain of mouse hepatitis virus (JHMV) was stimulated in vitro for 7 days. CTL were tested for recognition of target cells infected with either JHMV or vaccinia virus recombinants expressing the four virus structural proteins. Only target cells infected with either JHMV or the vaccinia virus recombinant expressing the JHMV nucleocapsid protein were recognized. Cytotoxic T cell lines were established by limiting dilution from the brains of mice undergoing acute demyelinating encephalomyelitis after infection with JHMV. Twenty of the 22 lines recognized JHMV-infected but not uninfected syngeneic target cells, indicating that they are specific for JHMV. All T-cell lines except one were CD8+. The specificity of the CTL lines was examined by using target cells infected with vaccinia virus recombinants expressing the JHMV nucleocapsid, spike, membrane, and hemagglutinin-esterase structural proteins. Seventeen lines recognized target cells expressing the nucleocapsid protein. Three of the JHMV-specific T-cell lines were unable to recognize target cells expressing any of the JHMV structural proteins, indicating that they are specific for an epitope of a nonstructural protein(s) of JHMV. These data indicate that the nucleocapsid protein induces an immunodominant CTL response. However, no CTL activity specific for the nucleocapsid protein could be detected in either the spleens or cervical lymph nodes of mice 4, 5, 6, or 7 days after intracranial infection, suggesting that the CTL response to JHMV infection within the central nervous system may be induced or expanded locally.

Enhanced antigen presentation in the absence of the invariant chain endosomal localization signal

The cytosolic tail of the major histocompatibility complex class II-associated invariant chain (Ii) molecule is thought to contain the endosomal localization signal that directs and/or retains newly synthesized class II within the endosomal antigen processing compartment. To determine the role of this signal in class II transport and antigen presentation we have generated class II-positive L cell transfectants that coexpress wild type or truncated forms of Ii. Deletion of the endosomal localization signal from Ii results in rapid transport of class II-Ii complexes to the cell surface. Once at the cell surface, the complex is efficiently internalized, Ii is degraded, and class II free of Ii is recycled back to the plasma membrane. Interestingly, the truncated form of Ii is still able to increase the efficiency of antigen presentation to T cells. These data suggest that the ability of Ii to enhance antigen presentation is not limited to Golgi apparatus-endosomal sorting and raise the possibility that endocytosed class II can form immunogenic complexes with newly processed antigen.

Phenotypic characterization of splenic T cells from mice infected with Plasmodium chabaudi chabaudi

T cells from spleens of mice infected with the erythrocytic stages of Plasmodium chabaudi chabaudi have been analysed with respect to their expression of surface molecules CD3, CD4 and CD8 and T-cell receptor (TCR) alpha beta and gamma delta. The majority of T cells from infected mice were alpha beta TCR+. However, there was an increase of approximately 8-10-fold in the proportion and total number of gamma delta T cells. Immunocytochemical analysis of sections of spleens taken from infected C57BL/6 mice during a primary infection showed that this increase took place particularly in the non-lymphoid areas. Within the alpha beta TCR+ T-cell population, both CD4+ T cells and CD8+ T cells were represented in proportions similar to those observed in normal uninfected mice. Stimulation of splenic T cells from infected mice with P. chabaudi-infected erythrocytes in vitro resulted in a blasted cell population composed predominantly of alpha beta TCR+ T cells with no preferential expansion of gamma delta TCR+ T cells. There was no evidence of superantigen-like stimulation of T cells bearing particular V beta chains of the TCR. The representation of the different V beta chains within the population was not significantly different from that seen in uninfected mice.

A new infectious mammary tumor virus in the milk of mice implanted with C4 hyperplastic alveolar nodules

We have previously characterized an infectious mouse mammary tumor virus [(MMTV(SW)] which induces a strong superantigen response in vivo. Here we describe the isolation and characterization of MMTV(C4) which was derived from milk of mice implanted with hyperplastic alveolar nodules. MMTV(C4) stimulates V beta 2 expressing T cells after local injection in vivo. Comparison with known open reading frame (orf) sequences revealed high homology to Mtv-6, an endogenous virus interacting with V beta 3-expressing T cells. The carboxyl-terminal amino acids were, however, altered. High homology including the carboxyl-terminal orf amino acids were found with MMTV(C3H-K). We show here that MMTV(C3H-K) has lost its superantigen function. Sequence comparisons permitted the characterization of few key amino acids which could be important for T cell receptor interaction and superantigen processing.

Precommitment of CD4+CD8+ thymocytes to either CD4 or CD8 lineages

CD4+ and CD8+ mature T cells arise from CD4+CD8+ precursors in the thymus. During this process, cells expressing T-cell receptors (TCRs) reactive with self major histocompatibility complex (MHC) class I or II molecules are positively selected to the CD8 or CD4 lineage, respectively. It is controversial whether lineage commitment of CD4+CD8+ thymocytes is controlled directly by TCR specificity for MHC (instructional model) or, alternatively, by processes that operate independently of TCR specificity (stochastic model). We show here that CD4+CD8+ thymocytes bearing a MHC class I-restricted transgenic TCR can be subject to two alternative developmental fates. One population of CD4+CD8+ cells is positively selected by MHC class I molecules to the CD8 lineage as expected, whereas the other CD4+CD8+ population rearranges endogenous TCR genes and is positively selected by MHC class II molecules to the CD4 lineage. Blocking TCR-MHC class II interactions in vivo does not interfere with the generation of CD4+CD8+ cells expressing endogenous TCRs but does prevent their subsequent maturation to CD4+ cells. These data support a version of the stochastic model in which CD4+CD8+ thymocytes are precommitted to the CD4 or CD8 lineage independently of TCR specificity for MHC and prior to positive selection.

Following a diabetogenic T cell from genesis through pathogenesis

Nonobese diabetic (NOD) mice spontaneously develop a disease very similar to type 1 diabetes in humans. We have generated a transgenic mouse strain carrying the rearranged T cell receptor genes from a diabetogenic T cell clone derived from a NOD mouse. Self-reactive T cells expressing the transgene-encoded specificity are not tolerized in these animals, resulting in rampant insulitis and eventually diabetes. Features of the disease process emphasize two so-called check-points, recognized previously in the NOD and human diseases but easily misinterpreted. Although NOD mice are protected from insulitis and diabetes by expression of the E molecule encoded in the major histocompatibility complex, the transgenics are not, permitting us to exclude some possible mechanisms of protection.

Thymic selection and thymic major histocompatibility complex class II expression are abnormal in mice undergoing graft-versus-host reactions

The graft-vs.-host reaction (GVHR) results in damage to the epithelial and lymphoid compartments of the thymus and thus in abnormal maturation and function of thymocytes in mice undergoing GVHR. In this report, the effects of GVHR on thymic T cell receptor (TCR) expression and usage have been investigated. GVHR was induced in unirradiated F1 hybrid mice by the intravenous transfer of parental lymphoid cells. Expression of the CD3/TCR complex on thymocyte subsets defined by CD4 and CD8 was studied by three-color flow cytometry. The level of CD3/TCR was decreased on CD4+CD8-, but not CD4-CD8+, mature thymocytes. The lack of upregulation of CD3/TCR on CD4 single-positive thymocytes, but not on their CD8+ counterparts, suggested an abnormality of class II major histocompatibility complex (MHC) expression in the thymuses of mice undergoing GVHR. Immunofluorescence staining of thymic frozen sections revealed that MHC class II expression was dramatically decreased in GVH-reactive mice. GVHR-induced changes in positive and negative selection were evaluated by determining the incidence of specific V beta TCR segment usage in the thymus. In normal mice, thymocyte usage of any given V beta segment was highly consistent between individuals of the same strain and age; however, a marked divergence in the incidence of TCR V beta 6hi and V beta 8hi cells between GVH-reactive littermate mice was observed, suggesting that thymic positive selection had become disregulated in these animals. Furthermore, negative selection was defective; the incidence of phenotypically self-reactive V beta 6hi T cells was significantly greater in the thymuses of GVH-reactive mice bearing the endogenous superantigen Mls-1a than in untreated controls. Thus, mice undergoing GVHR showed defective TCR upregulation on CD4+CD8- thymocytes and changes in TCR usage reflecting aberrant thymic selection, in conjunction with decreased expression of MHC class II. Most abnormalities of TCR expression and usage on CD4+ thymocytes observed in GVH-reactive mice were analogous to those of class II knockout mice.

Thymus-derived cytokine(s) including interleukin-7 induce increase of T cell receptor alpha/beta+ CD4-CD8- T cells which are extrathymically differentiated in athymic nude mice

Extrathymic T cell differentiation pathways have been reported, although the thymus is the main site of T cell differentiation. The thymus is also known to produce several cytokines that induce proliferation of thymocytes. In the present study, we investigated the influence of thymus-derived cytokines on extrathymic T cell differentiation by intraperitoneal implantation with a diffusion chamber which encloses fetal thymus (we named it fetal thymus-enclosed diffusion chamber, FTEDC) in athymic BALB/c nu/nu mice. Increase in number of T cells bearing T cell receptor (TcR) alpha/beta was detected in lymph nodes and spleens of FTEDC-implanted nude mice 1 week after implantation, whereas no such increase was detected in control nude mice implanted with a diffusion chamber without thymus. The FTEDC-induced increase of T cells was suppressed by intraperitoneal injection of anti-interleukin-7 monoclonal antibody (mAb). The TcR alpha/beta T cells in FTEDC-implanted BALB/c nu/nu mice preferentially expressed V beta 11, although V beta 11-positive T cells are deleted in the thymus of euthymic BALB/c mice by clonal elimination of self-super-antigen Dvb11-specific T cells. TcR alpha/beta T cells in FTEDC-implanted nude mice were of CD4-CD8- phenotype and showed no proliferative response against anti-TcR monoclonal antibody stimulation. These results suggest that the thymus can induce extrathymic T cell differentiation through the influence of thymus-derived cytokine(s) including interleukin-7, and that such extrathymically differentiated T cells have acquired only a little or no ability for proliferation when they recognize antigen by their TcR.

Allogeneic recognition of class I molecules: anti-H-2Ld repertoire of H-2b mice includes T cells recognizing mutant class II H-2b (Abm12) molecules

Two major histocompatibility complex (MHC) class I-reactive T cell clones derived from H-2b mice, generated against the allogeneic Ld molecule, were found to recognize the H-2b class II mutant Abm12 molecule as well. In addition, these clones also recognize the class II A(s) molecule, and display a class II-dependent reactivity to staphylococcal enterotoxin B. Neither the class I nor the class II alloreactivities of the clones were found to be dependent on other MHC molecules. Both clones express CD4+CD8- phenotypes. The CD4 molecule appears to be involved in their class II reactivity, while little or no role for CD4 could be detected in the class I reactivity. This is the first report of a class I/class II cross-reactivity being mediated by CD4+ T cells. The structural basis for this cross-reactivity is discussed.

T cell receptor targeting to thymic cortical epithelial cells in vivo induces survival, activation and differentiation of immature thymocytes

We report that targeting of T cell receptors (TcR) to non-major histocompatibility complex (MHC) molecules on thymic cortical epithelial cells by hybrid antibodies in vivo and in fetal thymic organ cultures results in phenotypic and functional differentiation of thymocytes. A single pulse with hybrid antibodies rescues immature, CD4/8 double-positive thymocytes from their programmed death in vivo, induces expression of the early activation antigen CD69 followed by TcR up-regulation, concomitant down-regulation of CD8 or CD4 and their conversion to functional mature T cells by day 3. This temporal sequence of maturation only affects small thymocytes without co-induction of blastogenesis. TcR targeting to MHC class II-positive epithelial cells predominantly induces CD4-positive T cells. This generation of CD4 single-positive T cells occurs also in MHC class II-deficient mice and thus is independent of CD4-MHC class II interactions. Moreover, in the presence of a specific deleting antigen (Mls 1a), TcR targeting results in transient activation of immature thymocytes, however, not in subsequent TcR (V beta 6) up-regulation and development of single-positive T cells. Our findings imply that TcR cross-linking to cortical epithelial cells is sufficient to confer a differentiation signal to immature thymocytes. Furthermore, this approach distinguishes two independent TcR-mediated intrathymic events: activation and subsequent deletion of the same thymocyte subset.

Peripheral lymphoid hyperplasia and central lymphoid depletion in mice treated with a bacterial B-cell mitogen (F3'EP-Si/p90)

In order to further understand the mechanism mediating the mitogenic and immunosuppressor effects of p90, a protein produced by Streptococcus intermedius, flow cytometric studies were performed on peripheral and central lymphoid organs of mice treated with this protein. p90 induced a strong blastogenic B-cell response in the spleen and lymph nodes, followed by a slight but significant polyclonal T-cell activation. B-cell repertoire analysis indicated that polyclonal B-cell responses affected similarly both CD5+ and conventional (CD5-) B cells in the spleen. Repertoire analysis of T cells failed to reveal any preferential stimulation of the V beta T-cell receptor (V beta-TcR) families studied. Peripheral lymphoid hyperplasia was observed concomitantly with central lymphoid depletion. In the bone marrow, pre-B and B cells were profoundly depleted, with a more pronounced effect on small pre-B cells. In the thymus, double-positive (CD4+CD8+) thymocytes were preferentially eliminated, with a relative enrichment of single positive (either CD4+ or CD8+) and double-negative (CD4-CD8-) thymocytes.

Another view of the selective model of thymocyte selection

Thymocyte commitment to the CD4 helper versus CD8 cytotoxic lineage has not been satisfactorily established. Two models have been elaborated: one based on instruction, the other on selection. Most previous results support the instructive model, but our comparison of thymocyte differentiation in MHC class II-, class I- and double-deficient mice provides data challenging it. There exists a significant population of CD4 single positive cells in class II-deficient animals that is intermediate in maturity between CD4+CD8+ and end-stage CD4+CD8- thymocytes and is selected on class I molecules; an equivalent CD8+CD4- population occurs in class I-deficient animals. We propose a selective model entailing two TCR-MHC molecule engagements: the first provokes random down-modulation of either CD4 or CD8 and a degree of differentiation; the second, requiring participation of the appropriate coreceptor, permits end-stage differentiation.

Clonal deletion of thymic mature T cells induced by staphylococcal enterotoxin B in murine fetal thymus organ culture

The present study aims at investigating the intrathymic maturational stage of T cells at which clonal deletion can be induced. Staphylococcal enterotoxin B (SEB) was added to organ cultures of murine fetal thymus lobes at various time points of culture, and V beta 8-expressing cells were assayed on day 14. V beta 8 low-expressing (V beta 8lo) cells were reduced to 40-60% of the control receiving no SEB, though the reduction was ambiguous when SEB was given on day 13. In marked contrast, V beta 8 high-expressing (V beta 8hi) cells were virtually completely deleted in all groups including the group given SEB on day 13. Most of the V beta 8hi cells that were deleted by 24 h of treatment with SEB were shown to be of the CD4+8- mature phenotype, though CD4-8+V beta 8hi cells were also deleted. It was further shown that the thymic V beta 8hi CD4+8- cells recovered from organs cultured for 14 days without SEB responded to immobilized anti-V beta 8 monoclonal antibody, indicating that V beta 8hi cells, which were highly sensitive to clonal deletion, were functionally competent mature T cells. These results strongly suggest that the thymus is capable of eliminating all T cells recognizing antigen present in the thymus regardless of the maturational stage of T cells.

A comparative study of T-cell receptor V beta usage in non-obese diabetic (NOD) and I-E transgenic NOD mice

The non-obese diabetic (NOD) mouse is a model for the study of insulin-dependent diabetes mellitus (IDDM). Recently transgenic NOD mice have been derived (NOD-E) that express the major histocompatibility complex (MHC) class II I-E molecule. NOD-E do not become diabetic and show negligible pancreatic insulitis. The possibility pertained that NOD-E mice are protected from disease by a process of T-cell deletion or anergy. This paper describes our attempts to discover whether this was so, by comparing NOD and NOD-E mouse T-cell receptor V beta usage. Splenocytes and lymph node cells were therefore tested for their ability to proliferate in response to monoclonal anti-V beta antibodies. We were unable to show any consistent differences between NOD and NOD-E responses to the panel of antibodies used. Previously proposed V beta were shown to be unlikely candidates for deletion or anergy. T cells present at low frequency (V beta 5+) in both NOD and NOD-E mice were shown to be as capable of expansion in response to antigenic stimulation as were more frequently expressed V beta. Our data therefore do not support deletion or anergy as mechanisms which could account for the observed disease protection in NOD-E mice.

Evidence for a preferential V beta usage by the T cells which adoptively transfer diabetes in NOD mice

Non-obese diabetic (NOD) mice become spontaneously diabetic as a result of a genetically programmed autoimmune process mediated by autoreactive T lymphocytes and directed against beta cell antigen(s). Studies dealing with T cell receptor (TcR) variable (V) gene usage by such autoreactive T lymphocytes have given contrasted results. Various reasons may explain these discrepancies: the multiplicity of antigenic epitopes putatively recognized by T cells, the ambiguity between specifically committed T cells and passenger lymphocytes homing randomly to the pancreas, the necessarily limited size of the T cell clone panels which have been analyzed for TcR rearrangements and, last but not least, the flexibility of T cell repertoires. To circumvent some of these difficulties, we have decided to concentrate upon the T cell population present in diseased animals and capable of transferring diabetes into young naive NOD recipients. This population, composed of CD4+ and CD8+ T cells, is presumably committed against the relevant beta cell antigens and is the most likely to reveal a bias in V gene usage if such a bias does indeed exist. To find out whether certain V beta genes are more frequently used than others by such pathogenic T cells, T lymphocytes from diabetic donors have been depleted in vitro of defined V beta subsets before being reinoculated into permissive recipients. Out of four V beta families probed under such conditions, three (V beta 8, V beta 5 and V beta 11) are neutral. Their absence neither increases nor reduces the final incidence of successful transfers, indicating that these gene segments are not preferentially used. In contrast, the depletion of V beta 6-positive T cells results in a severe reduction of transfers, suggesting that V beta 6 gene is used with a relatively high frequency by diabetogenic CD4+ and/or CD8+ T cells. To define more precisely which subset uses V beta 6 gene preferentially, we have performed mixing experiments with deleted and intact subsets. The results, based on disease transfer and insulitis severity, indicate that the V beta 6 bias affects predominantly the CD4+ subset. Thus, at variance with several studies concluding that V gene usage in NOD mice is heterogeneous, our present data suggest that disease transferring T cells use a relatively restricted set of V beta genes.

Progression to diabetes in nonobese diabetic (NOD) mice with transgenic T cell receptors

The T cell receptor (TCR) requirements in the pathogenesis of insulin-dependent diabetes were examined with transgenic NOD mice bearing nondisease-related TCR alpha and beta chains. In both TCR beta and TCR alpha beta transgenic NOD mice the beta chain transgene was expressed by > 98% of peripheral T cells. The alpha chain transgene was also highly expressed. Insulitis developed in both sets of transgenic animals with most of the lymphocytes in the lesion expressing the transgenic beta chain and with depletion of the endogenous TCR V beta genes. Nonetheless, NOD animals transgenic for TCR beta and TCR alpha beta developed diabetes similar to controls. Thus, skewing the TCR repertoire did not diminish autoimmune susceptibility in NOD mice.

Influence of viral superantigens on V beta- and V alpha-specific positive and negative selection

In mice, V beta-specific negative selection is mediated by a number of superantigens encoded by various mouse mammary tumor viruses. We have identified Mtv-3, Mtv-27, Mtv-44, Mtv-8, Mtv-9, Mtv-11, and MMTV(D2.GD), and have confirmed Mtv-1. Although specificities of superantigens correlate well with sequences of their carboxy terminal regions, Mtv-44 appears to be an exception: the product is specific for V beta 3, V beta 6, V beta 8.1, and V beta 9. It remains to be determined whether Mtv-44 produces one or two different superantigens to exhibit this specificity. V beta 5+ T-cell deletion is induced by two groups of superantigens: V beta 3-specific superantigens encoded by Mtv-1, Mtv-3, Mtv-6, Mtv-13, Mtv-27, and Mtv-44, and V beta 11-specific superantigens encoded by Mtv-8, Mtv-9, and Mtv-11. Furthermore, these V beta 3-specific superantigens are also specific for V beta 17a(cz). In contrast, V beta-specific positive selection and V alpha-specific positive and negative selection do not seem to involve non-H-2 (super)antigens, although their involvement can not be excluded. In the near future, superantigens, powerful modulators of T-cell functions, will be exploited for clinical applications.

Major histocompatibility complex-specific recognition of Mls-1 is mediated by multiple elements of the T cell receptor

We have recently shown that recognition of the mouse mammary tumor virus 9-associated superantigen (vSAG-9) by murine V beta 17+ T cells is strongly influenced by the major histocompatibility complex (MHC) class II haplotype of the presenting cells, resulting in a form of MHC-restricted recognition. This finding was unexpected, because T cell recognition of another well-characterized retroviral superantigen, minor lymphocyte-stimulating antigen 1 (Mls-1), had been shown to be independent of the MHC haplotype of the presenting cell. To determine whether recognition of vSAG-9 and Mls-1 is fundamentally different, we undertook an extensive analysis of MHC haplotype influences on vSAG-9 and Mls-1 recognition by panels of T cell hybridomas. Our results show that, although most hybridomas recognized Mls-1 regardless of the MHC haplotype of the presenting cells, as previously described by others, some hybridomas exhibited unique patterns of MHC fine specificity. Thus, T cell recognition of vSAG-9 and Mls-1 is not fundamentally different, but the apparent differences can be explained in terms of frequency. The MHC fine specificity of individual Mls-1-reactive hybridomas was influenced by both V beta and non-V beta T cell receptor (TCR) elements. First, the influence of the V beta element was apparent from the observation that V beta 8.2+ hybridomas were significantly more MHC specific in their recognition of Mls-1 than V beta 8.1 hybridomas. Second, a role for the TCR alpha chain was implicated from the distinct patterns of fine specificity of Mls-1 reactivity among a panel of transgenic hybridomas that expressed an identical beta chain (V beta 8.1D beta 2J beta 2.3C beta 2). Sequence analysis revealed that junctional residues of the TCR alpha chain and/or V alpha/J alpha combinations influenced the MHC haplotype fine specificity for Mls-1. Third, D beta J beta influences were implicated, in that the transgenic hybridomas expressed distinctive patterns of Mls-1 fine specificity not represented among V beta 8.1+ nontransgenic hybridomas. The findings that T cell recognition of endogenous superantigen is MHC specific, and that this specificity correlates with non-V beta elements of the TCR, support the hypothesis that there is a direct interaction between the TCR and either polymorphic residues of the MHC class II molecule or haplotype-specific dominant peptides presented by class II.

Characterization of experimental allergic encephalomyelitis-susceptible, Biozzi AB/H (H-2dq1) mice which express H-2Anod: analysis of T-cell receptor expression and the detection of a deletion ligand encoded by Mtv-7

Biozzi (H-2dq1) AB/H mice are marked not only by their high titre antibody responses following immunization with protein antigens but are also susceptible to experimental allergic encephalomyelitis (EAE) induction. The T-cell receptor (TcR) repertoire in this recently characterized strain was analysed. Biozzi AB/H mice were found to express the Thy-1a, Ly-1b, Ly-2b and Ly-5b alleles. Serological typing of the TcR-V beta + peripheral T cells suggested that the AB/H mice belong to the TcR-V beta b haplotype and express a deletion ligand for TcR-V beta 6+ and TcR-V beta 8.1+ T cells. This was confirmed by Southern blot analysis which revealed the presence of Mtv-17, Mtv-23, Mtv-31 (Y chromosome) and notably Mtv-7. Therefore the AB/H mice are Mls-1a. Despite the depletion/absence of the majority of TcR-V beta families in EAE-resistant (BALB/c) x EAE-susceptible (AB/H) F1 mice it was possible to induce EAE in these F1 animals. This suggests either that the deleted TcR-V beta-bearing T cells were not the principal encephalitogenic cells or that the TcR-V beta usage is sufficiently heterogeneous to accommodate such deletion events, in spinal cord-induced EAE.

CD8 T cells can protect against an intracellular bacterium in an interferon gamma-independent fashion

Specific T-cell immunity to Listeria monocytogenes is thought to occur through the action of lymphokines which activate phagocytes to ingest and kill microorganisms. Interferon gamma (IFN-gamma) has been shown to be an effective mediator of this type of macrophage activation in vivo and in vitro. The monoclonal antibody H22.1 efficiently neutralizes endogenous IFN-gamma, exacerbates disease in a mouse model of L. monocytogenes infection, and inhibits the in vivo protective activity of a Listeria antigen-specific CD4 T-cell line. In contrast, in vivo protection by Listeria-immune CD8 T cells is not inhibited by the neutralizing anti-IFN-gamma monoclonal antibody. These results suggest that CD8 T cells can protect against an intracellular pathogen in an IFN-gamma-independent manner.

Development of T cell receptor alpha beta-bearing T cells in the submersion organ culture of murine fetal thymus at high oxygen concentration

Organ culture (OC) of murine fetal thymuses on a membrane filter floating on the medium has been used as an important strategy in studies of the mechanism of T cell development. On the other hand, the submersion organ culture (S-OC) system, in which fetal thymus lobes are submerged in the culture medium, is not popularly used because the growth of T cells is much lower than that in OC at the air-medium border (AMB-OC). In the present work, we tried to culture the fetal thymuses in the S-OC system at 5% CO2 and various concentrations of O2. We found that in the environment containing 5% O2, gamma delta T cells were selectively generated, though the cell recovery was less than one-tenth of that seen in AMB-OC. Generation of gamma delta T cells was hardly affected by increasing the O2 concentration. In marked contrast, the development of alpha beta T cells was highly dependent upon the O2 concentration. In the S-OC at more than 60% O2, differentiation and growth of T cells, as determined in terms of recovered cell number, CD4 vs. CD8 profile and predominance of alpha beta lineage, were comparable to those observed in AMB-OC. It was further shown that clonal deletion of V beta 6+ T cells occurred in high O2 S-OC of CBA/J (Mls-1a) but not C3H/HeJ (Mls-1b) mice, the extent of the deletion being low but comparable with that seen in AMB-OC. These results indicated that the fetal thymus microenvironment was potentially capable of supporting the development of both gamma delta and alpha beta T cells, and that skewing to one of these lineages was determined by an additional factor(s) such as the concentration of O2 dissolved in the medium.

Calpain may produce a Ca(2+)-independent form of kinase C in long-term potentiation

Both an enhancement of Ca(2+)-independent kinase activity in the supernatant fraction and enhanced breakdown of type beta kinase C (PKC-beta) were observed in the hippocampus after induction of tetanus-induced long-term potentiation (LTP) in the hippocampal CA1 region of rat. The enhanced activity was inhibited by the PKC-specific inhibitor, PKC19-36. Both phenomena were also observed simultaneously in the in vitro model system in which hippocampal homogenate was treated with CaCl2, and both enhancements were inhibited by the addition of calpain inhibitors, leupeptin and benzyloxycarbonyl-Leu-Met-H. The results suggest that Ca(2+)-independent kinase activity enhanced in the supernatant fraction during LTP derives from the catalytic fragment of PKC-beta released by calpain.

Selective activation of murine V beta 8.2 bearing T cells by Pseudomonas exotoxin A

We have determined that Pseudomonas aeruginosa exotoxin A (PE) can selectively stimulate the proliferation of V beta bearing T lymphocytes. Murine thymocytes were fractionated by selective agglutination with peanut agglutinin (PNA) and the PNA- thymocytes, which represent mature thymocytes, were shown to be responsive to PE stimulation. In addition, mature peripheral T lymphocytes (nylon wool nonadherent splenocytes) were also observed to respond to PE stimulation. Both CD4+ and CD8+ splenic T lymphocyte populations proliferated in response to PE. Flow microfluorimetry analysis of PNA- thymocytes stimulated with PE indicated that V beta 8.2 bearing T cells were preferentially expanded. Thus, our data indicate that PE represents a microbial super antigen which stimulates murine thymocytes which bear the V beta 8.2 element of the T cell receptor.

Macrophages, T cell receptor usage, and endothelial cell activation in the pancreas at the onset of insulin-dependent diabetes mellitus

Current knowledge of the phenotype of mononuclear cells accumulating in pancreatic islets in insulin-dependent diabetes (IDDM) and factors determining their homing into the pancreas is limited. Therefore, a pancreas obtained at the onset of IDDM was studied in detail. Cryostat sections were stained for mononuclear cell types, T cell receptor subtypes, and adhesion molecules of vascular endothelium and studied by immunofluorescence microscopy, and peripheral blood mononuclear cells were phenotyped using flow cytometry. Monocytes/macrophages (lysozyme- or CD 14-reactive cells) were identified among other mononuclear cell types in islet infiltrates. V beta 8-positive T cells were overrepresented, but T cells with other V beta s studied (V beta 5, V beta 5.1, V beta 6, V beta 12) were also found. The vascular endothelium of the islets and many small vessels nearby islets strongly expressed intercellular adhesion molecule-1, whereas vascular cell adhesion molecule-1 and E-selectin were totally absent. We conclude: (a) that increased expression of intercellular adhesion molecule-1 on vascular endothelium may increase endothelial adhesion of mononuclear cells and enhance their accumulation in the pancreas during diabetic insulitis; (b) that T cells with certain T cell receptors can be enriched in infiltrated pancreatic islets; and (c) that macrophages and antigen-specific CD 8-positive T cells are involved in pancreatic beta cell destruction at the onset of IDDM.

CD4 expression is differentially required for deletion of MLS-1a-reactive T cells

Clonal deletion of thymocytes expressing potentially self-reactive T cell receptors (TCRs) occurs during thymocyte ontogeny. Mice deficient for CD4 expression provide a unique model system to study the contribution of the CD4 molecule in negative selection of T cells reactive against the major histocompatibility complex class II-associated retroviral self-superantigen, Mls-1a. In the presence of Mls-1a determinants, mature CD8+ T cells expressing V beta 6, 8.1, and 9 were deleted in CD4-deficient mice, thus demonstrating that TCR affinity for Mls-1a is sufficient for deletion and that a signal through CD4 was not required. However, in instances where the TCR affinity for Mls-1a is low, as in the case of V beta 7+ T cells, CD4 expression was required for clonal deletion. These results demonstrate that for Mls-1a-mediated clonal deletion of T cells, the requirement for the accessory or coreceptor function of CD4 depends on the affinity of the TCR.