Role of T cell receptor V beta genes in Theiler's virus-induced demyelination of mice.

Intracerebral infection of certain strains of mice with Theiler's virus results in chronic immune-mediated demyelination in spinal cord. We used mouse mutants with deletion of the V beta class of TCR genes to examine the role of TCR genes in this demyelinating disease which is similar to multiple sclerosis. Quantitative analysis of spinal cord lesions demonstrated a markedly increased number and extent of demyelinated lesions in persistently infected RIII S/J mice which have a massive deletion of the TCR V beta-chain (V beta 5.2, V beta 8.3, V beta 5.1, V beta 8.2, V beta 5.3, V beta 8.1, V beta 13, V beta 12, V beta 11, V beta 9, V beta 6, V beta 15, V beta 17) compared with B10.RIII mice which are of identical MHC haplotype (H-2r) but have normal complement of V beta TCR genes. In contrast, infection of C57L (H-2b) or C57BR (H-2k) mice which have deletion of the V beta TCR genes (V beta 5.2, V beta 8.3, V beta 5.1, V beta 8.2, V beta 5.3, V beta 8.1, V beta 13, V beta 12, V beta 11, and V beta 9) resulted in few demyelinating lesions. Genetic segregation analysis of (B10.RIII x RIII S/J) x RIII S/J backcrossed mice and (B10.RIII x RIII S/J) F2 mice demonstrated correlation of increased susceptibility to demyelination with deletion of TCR V beta genes. The increase in number of demyelinating lesions correlated with increase in number of virus-Ag+ cells in spinal cord. These experiments provide strong evidence that the structural diversity at the TCR beta-complex can influence susceptibility to virus-induced demyelination.     

Role of Mls-1 locus and clonal deletion of T cells in susceptibility to collagen-induced arthritis in mice

The role of T cell-mediated and humoral immunity to type II collagen has been well documented in collagen-induced arthritis (CIA). Previous work from our laboratory has indicated that genomic deletions of TCR V beta genes may play a role in CIA resistance in mice. This indicated a selectivity of TCR usage by autoreactive T cells in CIA in mice. Certain strains of mice, although having a normal genomic V beta TCR repertoire, can show clonal deletion of peripheral T cells that bear specific V beta gene products in their TCR. These clonally deleted T cells are reactive with self-Ag such as minor lymphocyte stimulation (Mls) Ag. An Mls-congenic strain, BALB.D2.Mlsa, which differs only at the Mls-1 a locus from BALB/c (Mls-1b), was used to examine the effect of clonal deletion of Mls-1a-reactive T cells in CIA. These two strains were crossed to three CIA-susceptible strains, B10.RIII (H-2r, Mls-1b), DBA/1 (H-2q, Mls-1a), and B10.Q (H-2q, Mls-1b), and the crosses were injected with type II collagen. A significantly decreased incidence of arthritis was observed in the (BALB.D2.Mlsa x B10.Q)F1 hybrids, compared with (BALB/c x B10.Q)F1 hybrids, upon immunization with chick type II collagen. The BALB.D2.Mlsa cross mice also had significantly lower levels of antimouse collagen antibodies. Flow cytometric analysis confirmed the clonal deletion of Mls-1a-reactive V beta 8.1, V beta 6, V beta 7, and V beta 9 subsets in the (BALB.D2.Mlsa x B10.Q)F1 hybrids. The study of H-2q/d mice in (BALB.D2.Mlsa x B10.Q) x B10.Q back-crosses demonstrated a significant correlation between CIA resistance and Mls-1a locus. On the other hand, B10.RIII crosses showed only a modest decrease in CIA incidence in the presence of Mls-1a. As expected, all the DBA/1 crosses had an equal incidence of CIA, which was somewhat less than that seen in DBA/1 mice themselves. These studies point out that the Mls-1a locus could play a role in decreasing CIA incidence by clonal deletion of T cells bearing specific V beta TCR, which may be involved in the pathogenesis of CIA. The influence of the clonal deletion of T cells on CIA, and hence the usage of specific V beta TCR by autoreactive anti-type II collagen T cells, however, depends not only on the source of the type II collagen and the MHC class II molecules involved but also on other background genes in mice.     

Evidence for a role for T cell receptors (TCR) in the effector phase of acute bone marrow graft rejection. TCR V beta 5 transgenic mice lack effector cells able to cause graft rejection.

Lethally irradiated mice reject within 24 h certain marrow grafts, a phenomenon called either allogeneic or hybrid resistance. The cells responsible for this rejection (NK1+ CD3+ cells (TNK) express Ag of NK cells as well as the TCR-associated CD3 complex. This raises the question whether TCR participate in the function of these cells during graft rejection. By using flow cytometry it is shown that the majority of TNK cells expresses the TCR-alpha/beta chains and by using adoptive cell transfer assays evidence is presented that it is the TCR-alpha/beta expressing cells that cause rejection. To explore whether any particular TCR chains have to be expressed on these cells, C57L mice were assayed and found to be responders suggesting that the V beta chains deleted in these mice are not obligatory. However, introduction of a specific TCR V beta 5 chain into C57BL/6 mice as a transgene leads to inability to transfer resistance. TNK cells of V beta 5 transgenic mice express the introduced gene suggesting that it is the transgenic TCR that is responsible for the lack of function. In assessing T cell functions in V beta 5 transgenic mice it is shown that although these mice generate CTL specific for H-2d targets there is a deficiency to recognize H-2Dd, i.e., of determinants presumed to be recognized in the acute rejection mechanism. Thus TNK cells and CTL share the inability to recognize H-2Dd epitopes due to expression of the V beta 5 transgene. The notion that TCR on TNK cells play a role in the acute rejection process makes it necessary to postulate a receptor selection mechanism for these cells.     

The influence of self-MHC and non-MHC antigens on the selection of an antigen-specific T cell receptor repertoire

We have examined the influence of self-Ag on TCR expression and specificity in the immune response to the Ag pigeon cytochrome c. Previous work has shown that most Ek-restricted cytochrome c-specific T cells from B10 background mice express TCR alpha beta-heterodimers encoded by V beta 3 and V alpha 11 genes, but that T cells expressing V beta 3 proteins are eliminated due to self-tolerance in Mls-2a mouse strains. Thus, EK-restricted cytochrome c-specific T cells from Mls-2a mice fail to express any V beta 3. In the current study the influence of self-MHC and non-MHC Ag on TCR usage in the immune response to cytochrome c was further examined. First, it was demonstrated that the absence of V beta 3 expression in Mls-2a mice does not alter Ir gene function. Specifically, Mls-2a/Eb haplotype V beta 3- [C3H.SW x B10.A(5R)]F1 mice were high responders to cytochrome c despite the fact that previous structure function analyses have shown a very close correlation between Eb-restricted cytochrome c recognition and V beta 3 expression. This demonstration of the plasticity of TCR expression suggests that relatively few Ir gene defects result from tolerance induced by self-Ag. We also examined differences in V alpha 11 expression among cytochrome c-specific T cells from various H-2k haplotype mouse strains. In particular, the low level of expression of V alpha 11 in cytochrome c-specific T cells from C57BR (H-2k) mice was shown not to be due to self-tolerance. Rather, evidence for limited strain polymorphism of V alpha 11 genes, plus the fact that cytochrome c-specific T cells from F1 hybrids between H-2k, Mls-2b identical C57BR and B10.BR mice express high levels of V alpha 11, suggested the possibility that the variable V alpha 11 usage in the cytochrome c-specific responses of these two strains reflected differences in positive selection during ontogeny by non-MHC non-Mls self-Ag.     

The role of C5 and T-cell receptor Vb genes in susceptibility to collagen-induced arthritis

Collagen-induced arthritis (CIA) is a rodent arthritis model in which immunization with heterologous type II collagen induces an inflammatory polyarthritis. Susceptibility to the disease is mediated by major histocompatibility complex (MHC) genes as well as genes at other loci. Previous studies of the SWR/J mouse strain, which is resistant to CIA despite bearing the susceptible H-2 ^q haplotype, have suggested that this resistance is the result of a deletion of T-cell receptor (Tcr) Vb gene segments which is carried by this strain. Other studies have implicated a deficiency in complement component C5 as the cause for the resistance. In order to assess the relative importance of these two genes in susceptibility to CIA, and to provide an estimate of the number of independent genes involved in the disease, we analyzed 196 F₂ progeny of a (DBA/1 × SWR/J) cross for arthritis susceptibility, and expression of both C5 and Tcr genes. Thirty of the F₂ progeny developed arthritis. All of the arthritic mice had at least one copy of the wild-type C5 allele, while the Tcr-Vb haplotypes were distributed in Mendelian fashion. These results demonstrate that C5 sufficiency is an absolute requirement for CIA, but that Tcr-Vb genes located within the SWR deletion have little influence. Genetic analysis of the incidence rate suggests that there is polygenic control of susceptibility to CIA and that in addition to H-2, 5–6 other independent loci (including C5) may be involved.     

Extrathymic positive selection of gamma delta T cells. V gamma 4J gamma 1 rearrangements with "GxYS" junctions.

Neither function nor Ag recognition properties of gamma delta T cells are well understood yet. A TCR gamma-chain family, characterized by distinct N region sequences that converge in coding for a "GxYS" VJ junctional sequence, appears late in ontogeny among highly diversified V gamma 4J gamma 1C gamma 1 chains of C57BL/6 and BALB/c mice. The glycine and serine codons are of germline V gamma 4 and J gamma 1 origin, respectively, whereas the N region consists of a variable amino acid residue x, followed by an invariant tyrosine Y. The high expression of V gamma 4 xYJ gamma 1C gamma 1 in the lung of BALB/c mice compared to that of C57BL/6 is apparently due to a novel pattern of strain-dependent positive selection which, unlike for alpha beta TCR, operates extrathymically. This type of selection seems to be determined by strain specific polymorphic ligands encoded outside of the classical H-2 region.     

T-cell receptor Vbeta deletion and Valpha polymorphism are responsible for the resistance of SWR mouse to arthritis induction

 Collagen type II-induced arthritis (CIA) develops in susceptible mouse strains after intradermal injections of type II collagen (CII) in complete Freund's adjuvant (CFA). Susceptibility to CIA in mice is linked to genes of the major histocompatibility complex (MHC). Although the SWR mouse has a susceptible MHC haplotype (H2 ^q ), it is resistant to CIA. SWR exhibits at least two known immunological defects: (1) it contains a germline deletion of about 50% of T-cell receptor (TCR) Vβ-chain gene segments, and (2) SWR is deficient in complement component C5. It has been shown that T cells that express TCRVα11.1 and TCRVβ8.2 play a substantial role in the pathogenesis of arthritis in the DBA/1 mouse (H2 ^q ). We generated SWR transgenic (tg) mice to determine whether the expression of pathogenic Vα11.1 and/or Vβ8.2 transgenes would confer arthritis susceptibility. Arthritis was induced in the SWR TCRαβ tg mice, but not in SWR TCRβ tg mice. To address the role of Vα11.1 in arthritis susceptibility, we examined the allelic polymorphisms of the Tcra-V11-gene subfamily members between the arthritis susceptible DBA/1 mouse and the arthritis-resistant SWR mouse strain. The amino acid sequences of the Vα11.1 alleles differ at two positions (codons 18 and 68). Accordingly, these two amino acid changes are sufficient to allow the production of pathogenic T cells in SWR mice. This is the first demonstration of the association of a particular Tcra-V allele and arthritis susceptibility in mice. Received: 20 November 1998 / Revised: 15 February 1999     

Circulating immune complexes augment severity of antibody-mediated myasthenia gravis in hypogammaglobulinemic RIIIS/J mice

Experimental autoimmune myasthenia gravis (EAMG) is severe in RIIIS/J mice, despite a significant B cell immunodeficiency and a massive TCR V beta gene deletion. Severity of EAMG in RIIIS/J mice is greater than MHC-identical (H-2(r)) B10.RIII mice, suggesting the influence of non-MHC genes as an EAMG-potentiating factor in this strain. To delineate the role of deleted TCR V beta genes in RIIIS/J mice, we obtained (RIIIS/J x B10.RIII)F(1) (V beta(b/c)) x RIIIS/J (V beta(c)) backcross mice using Mendelian genetic methods and immunized them with acetylcholine receptor. EAMG susceptibility was not elevated in mice with V beta(c) genotype having 70% V beta gene deletion. Next, we performed microarray analysis on 12,488 spleen cDNAs obtained from spleens of naive RIIIS/J and B10.RIII mice. In RIIIS/J mice, 263 cDNAs were overexpressed and 303 cDNAs were underexpressed greater than 2-fold, compared with B10.RIII mice. TCR gene expression was augmented, whereas NK receptor, C1q, and C3 gene expressions were diminished in RIIIS/J mice. RIIIS/J mice also had increased lymph node T cell counts, elevated serum anti-AChR Ab levels, and serum C3 and C1q-conjugated circulating immune complex levels. A direct correlation between increased serum C1q-conjugated circulating immune complex levels and disease severity was observed in RIIIS/J mice.     

Genetic analysis of diabetes in the nonobese diabetic mouse. I. MHC and T cell receptor beta gene expression

Backcross nonobese diabetic (NOD) ((NOD x SWr)F1 x NOD) mice (108 females and 105 males) were typed for MHC, TCR V beta, and monitored for 350 days for the onset of diabetes. The presence of "antipolar" antibodies in the sera and the occurrence of insulitis was examined in a proportion of these backcross mice. There was no difference in the incidence of diabetes in mice heterozygous for TCR V beta b/a vs those homozygous for TCR V beta b/b. Among the 17 diabetics (all female) detected in this backcross, 14/17 were H-2nod/nod but 3/17 were H-2nod/q. This supports a previous observation suggesting that the MHC-linked diabetogenic gene originally thought to be recessive may rather be dominant but have a low penetrance in the heterozygous state. Antipolar autoantibodies were found in both female and male backcross mice, and were similarly distributed in diabetic and nondiabetic mice. There appeared to be no correlation between the level of these auto-antibodies and development of diabetes. The incidence and severity of insulitis was linked to MHC but no influence of TCR genes on insulitis nor an association between insulitis and antipolar antibodies could be demonstrated in this study. Further analyses of H-2nod/nod intercross mice homozygous for TCR V beta a or TCR V beta b are currently underway.     

Similarity and difference in the mechanisms of neonatally induced tolerance and cyclophosphamide-induced tolerance in mice

The mechanisms of cyclophosphamide (CP)-induced tolerance were investigated by comparing with those of neonatally induced tolerance. When C3H/He Slc (C3H; H-2k, Mls-1b) mice were given i.v. either AKR/J Sea (AKR; H-2k, Mls-1a) or (AKR x C3H)F1 (AKC3F1; H-2k, Mls-1a/b) spleen cells and treated i.p. with CP 2 days later, a long-lasting skin allograft tolerance to AKR was induced in each case without any signs of graft-vs-host disease (GVHD). However, typical signs of GVHD were observed in the C3H mice neonatally tolerized with AKR spleen cells, but not in those tolerized with AKC3F1 spleen cells. The expression of TCR V beta 6, which is strongly correlated with the reactivity to Mls-1a Ag (of donor AKR origin), in the periphery was quite different between the two types of tolerant C3H mice. Namely, in the lymph nodes of the C3H mice tolerized with AKR spleen cells and CP, only CD4(+)-V beta 6+, but not CD8(+)-V beta 6+, T cells selectively disappeared, whereas both of them were abrogated in the lymph nodes of the C3H mice neonatally tolerized of AKR. By contrast, in the thymus of the two types of tolerant C3H mice, both CD4+CD8- and CD4-CD8+ single-positive thymocytes expressing TCR V beta 6 were clonally deleted, suggesting that the thymic involvement was the same in each type of tolerance. These results suggest that the preferential disappearance of the CD4(+)-V beta 6+ T cells (of host origin) and the effector T cells of GVHD (of donor origin) occurred only in the periphery of the C3H mice tolerized with AKR spleen cells plus CP and was attributable to the destruction of Ag-stimulated T cells by the CP treatment. In contrast, the intrathymic clonal deletion of immature V beta 6+ T cells was a common mechanism for both of the tolerance induction systems.     

Altered expression of self-reactive T cell receptor V beta regions in autoimmune mice.

Intrathymic tolerance results in elimination of T cells bearing self-reactive TCR V beta regions in mice expressing certain combinations of I-E and minor lymphocyte stimulatory (Mls) phenotypes. To determine if autoimmune strains of mice have a defect in intrathymic deletion of self-reactive TCR V beta regions, expression of V beta 3, V beta 6, V beta 8.1, and V beta 11 were examined in lpr/lpr and +/+ strains of mice; MRL/MpJ(H-2K, I-E+, Mlsb,), C57BL/6J(H-2b, I-E-, Mlsb,), C3H/HeJ(H-2k, I-E+, Mlsc), AKR/J(H-2k, I-E+, Mlsa); and in autoimmune NZB/N(H-2d, I-E+, Mlsa) and BXSB(H-2b, I-E-, Mlsb) mice. The results suggest that, during intrathymic development, self-reactive T cells are deleted in autoimmune strains of mice as found in normal control strains of mice. However, the TCR V beta repertoire is skewed in autoimmune strains compared to normal strains of mice. For example, MRL-lpr/lpr mice, but not other lpr/lpr strains, had increased expression of V beta 6 relative to expression in control MRL(-)+/+ mice, which is associated with collagen-induced arthritis. These data are consistent with a model of normal affinity for negative selection of self-reactive T cells in the thymus of autoimmune strains of mice followed by expansion of autoreactive T cell clones in the peripheral lymphoid organs. The peripheral lymphoid organs of lpr/lpr mice contain an expanded population of abnormal CD4-, CD8-, 6B2+ T cells. Elimination of self-reactive peripheral T cells suggests that these abnormal cells are derived from a CD4+ subpopulation in the thymus. Flow cytometry analysis of peripheral lymph node T cells from MRL-lpr/lpr mice reveal three populations of CD4+ T cells expressing low, intermediate and high intensity of B220 (6B2). This supports the hypothesis that in lpr/lpr mice, self-reactive CD4+ T cells are eliminated in the thymus, and that these cells lose expression of CD4 and acquire expression of 6B2 in the periphery.     

Predominant T cell receptor gene elements in TNP-specific cytotoxic T cells.

H-2b class I-restricted, TNP-specific CTL clones were obtained by limiting dilution cloning of either short term polyclonal CTL lines or spleen cells of TNP-immunized mice directly ex vivo. Sequence analyses of mRNA coding for TCR alpha- and beta-chains of 11 clones derived from CTL lines from individual C57BL/6 mice revealed that all of them expressed unique but clearly nonrandom receptor structures. Five alpha-chains (45%) employed V alpha 10 gene elements, and four of those (36%) were associated with J beta 2.6-expressing beta-chains. The alpha-chains from these four TCR, moreover, contained an acidic amino acid in position 93 of their N or J region-determined sequences. Clones isolated directly from spleen cells carried these types of receptors at lower frequency, 27% V alpha 10 and 19% J beta 2.6, indicating that bulk in vitro cultivation on Ag leads to selection for these particular receptors. However, even in TNP-specific CTL cloned directly ex vivo, V alpha 10 usage was increased about fivefold over that in Ag-independently activated T cells in H-2b mice (4 to 5%). The selection for V alpha 10/J beta 2.6-expressing cells was obtained repeatedly in other TNP-specific CTL lines from C57BL/6 mice but not in FITC-specific CTL from the same strain or in TNP-specific CTL lines from B10.BR (H-2k) or B10.D2 (H-2d) mice. We conclude from this (a) that the selection for V alpha 10/J beta 2.6+ T cells is driven by the complementarity of these receptors to a combination of TNP and MHC epitopes and (b) that predominant receptor structures reflect the existence of a surprisingly limited number of "T cell-relevant" hapten determinants on the surface of covalently TNP-modified cells.     

Preferential use of a T cell receptor V beta gene by acetylcholine receptor reactive T cells from myasthenia gravis-susceptible mice.

Experimental autoimmune myasthenia gravis (EAMG) is an important model for testing current concepts in autoimmunity and novel immunotherapies for autoimmune diseases. The EAMG autoantigen, acethylcholine receptor (AChR), is structurally and immunologically complex, a potential obstacle to the application of therapeutic strategies aimed at oligoclonal T cell populations. Inasmuch as we had previously shown that the clonal heterogeneity of T cell epitope recognition in EAMG was unexpectedly limited, we examined TCR V beta expression. AChR primed lymph node T cells and established AChR reactive T cell clones from EAMG-susceptible C57BL/6 (B6; H-2b, Mls-1b) mice showed preferential utilization of the TCR V beta 6 segment of the TCR. After in vivo priming and in vitro restimulation for 7 days with AChR or a synthetic peptide bearing an immunodominant epitope, V beta 6 expressing lymph node cells (LNC) were expanded several-fold, accounting for up to 75% of recovered viable CD4+ cells. The LNC of B6.C-H-2bm12 (bm12; H-2bm12, Mls-1b) mice, which proliferated in response to AChR but not to the B6 immunodominant peptide, failed to expand V beta 6+ cells. Inasmuch as nonimmune bm12 and B6 animals had similar numbers of V beta 6+ LNC (4-5%), this suggested that structural requirements for TCR recognition of Ag/MHC complexes dictated V beta usage. Results concerning peptide reactivity and V beta 6 expression among T cells from (B6 x bm12)F1 animals also suggested that structure-function relationships, rather than negative selection or tolerance, accounted for the strain differences between B6 and bm12. To examine the potential effects of thymic negative selection of V beta 6+ cells on the T cell response to AChR, CB6F1 (H-2bxd, Mls-1b; V beta 6-expressing) and B6D2F1 (H-2bxd, Mls-1axb; V beta 6-deleting) strains were analyzed for AChR and peptide reactivity and V beta 6 expression. Both F1 strains responded well to AChR but the response of B6D2F1 mice to peptide was significantly reduced compared to CB6F1. Short and long term cultures of peptide-reactive B6D2F1 LNC showed no expansion of residual V beta 6+ cells, although similar cultures of CB6F1 LNC were composed of more than 60% V beta 6+ cells. The results from the F1 strains further indicated that the T cell repertoire for peptide was highly constrained and that non-V beta 6 expressing cells could only partially overcome Mls-mediated negative selection of V beta 6+ TCR capable of recognizing peptide.(ABSTRACT TRUNCATED AT 400 WORDS)     

Thymic deletion of V beta 11+, V beta 5+ T cells in H-2E negative, HLA-DQ beta+ single transgenic mice

DQw6b transgenic mice have been generated by microinjecting a linearized cosmid clone containing 34-kb DQb genomic DNA, isolated from HLA-homozygous B cell line AKIBA (DR2, Dw12, DQw6), into embryos of (CBA x B10.M)F2 or (SWR x SJL)F2. Among 85 mice screened, eight mice were transgene-positive. The transgene in seven of eight founders was germline-transmitted. FACS analysis and immunohistochemical studies with DQ beta-specific mAb demonstrated that DQ beta molecules in association with mouse A alpha f molecules are expressed on peripheral mononuclear cells, spleen cells, and in thymic medulla. More interestingly, V beta 11-, V beta 5.1-, and V beta 5.2-bearing T cells, but not V beta 8.2-bearing T cells, were clonally deleted in the H-2E-negative but DQ beta+ progeny of two selected founders (260-23 and 258-10). The deletion was found to take place intrathymically during the transition stage from immature to mature thymocyte development. We postulate that although human DQ genes are more homologous to mouse H-2A genes, A alpha f/DQ beta hybrid molecules may possess the same self-peptide- (or superantigen)-presenting epitope as E alpha/E beta molecules critical for deletion of V beta 11-, V beta 5.1-, and V beta 5.2-bearing T cells in thymus. Our results also confirm the previous findings that accessory molecules on thymocytes such as CD4 may be involved in thymic selection, and further suggest that an interaction of mousE CD4 and mouse A alpha chain is required for the clonal deletion.     

T cell tolerance to self antigens in New Zealand hybrid mice with lupus-like disease

We determined if self-reactive T cells are able to escape thymic tolerance in autoimmune New Zealand mice. T cells utilizing V beta 17a and V beta 11 encoded receptors have been shown to be clonally eliminated in nonautoimmune mice expressing I-E because of their potential self-reactivity. Similarly, V beta 8.1+ and V beta 6+ T cells are tolerized in the thymus of nonautoimmune mice that express Mls-1a. These T cell subsets were quantitated in the lymph nodes and spleens of (NZB x NZW)F1 and (NZB x SWR)F1 mice. In young mice from both autoimmune strains, deletion was similar to that observed in control animals matched for I-Ed and Mls-1a expression. Furthermore, older female autoimmune mice with elevated levels of IgG antinuclear antibodies and severe lupus-like renal disease did not demonstrate evidence of a global tolerance defect. We also found that the levels of residual V beta 17a+ cells in MHC-matched control F1 strains were further reduced by up to 80% in autoimmune (NZB x SWR)F1 mice. The greater in vivo elimination corresponded to an enhanced ability of NZB spleen cells, compared with other H-2d spleen cells, to stimulate V beta 17a+ hybridomas in vitro. The increased stimulation in culture could not be attributed to quantitative differences in I-E Ag expression. The results suggest that autoreactive T cells have been eliminated in these autoimmune mice by normal mechanisms of self-tolerance. Furthermore, the data demonstrate the existence of an NZB minor locus not present in other H-2d strains that influences T cell repertoire and enhances stimulation of T cells potentially reactive to self class II MHC Ag.     

Evidence that Mls-2 antigens which delete V beta 3+ T cells are controlled by multiple genes

V beta 3+ T cells are eliminated in Mls-2a mice carrying some, but not all, H-2 types. Analysis of AKXD and BXD recombinant inbred strains showed that Mls-2a (formerly Mlsc) was not the product of a single gene and suggested that at least two non-H-2 genes control V beta 3 levels. Studies of the progeny of a B10.BR x (C3H/HeJ x B10.BR)F1 backcross confirmed the existence of two V beta 3+ T cell deleting genes: one unlinked and one linked to Ly-7, which we propose be called Mls-2 and Mls-3, respectively. Mls-2a induces partial deletion of V beta 3+ T cells with a bias toward deleting CD4+ cells. It stimulates V beta 3+ hybrids and may be linked to Mtv-13 on chromosome 4. A third non-H-2 gene is implicated in enhancing the presentation of Mls-2a. Mls-3a causes elimination of all V beta 3+ T cells in H-2k and H-2d mice but poorly stimulates V beta 3+ hybrids.     

Radiation leukemia virus-induced thymic lymphomas express a restricted repertoire of T-cell receptor V beta gene products.

We have investigated the phenotypic changes that take place during the process of neoplastic transformation in the thymocytes of C57BL/Ka mice infected by the radiation leukemia virus (RadLV). By the combined use of antibodies against the envelope glycoprotein gp70 of RadLV, the transformation-associated cell surface marker 1C11, and the CD3-T-cell receptor (TCR) complex, we found that in the RadLV-infected thymus, the earliest expression of viral gp70 is in 1C11hi cells; a small but significant percentage of these cells also express CD3. A first wave of viral replication, manifested by the expression of high levels of gp70 in thymocytes (over 70% positive), reaches a peak at 2 weeks; during this period, no significant changes are observed in the expression of 1C11 or CD3. The population of gp70+ cells is drastically reduced at 3 to 4 weeks after infection. However, a second cohort of gp70+ cells appears after 4 weeks, and these cells express high levels of 1C11 and TCR determinants as well. RadLV-induced lymphomas differ from normal thymocytes in their CD4 CD8 phenotype, with domination by one or more subsets. Characterization of TCR gene rearrangements in RadLV-induced lymphomas shows that most of these tumors are clonal or oligoclonal with respect to the J beta 2 TCR gene, while the J beta 1 TCR gene is rearranged in a minority (4 of 11) of lymphomas. TCR V beta repertoire analysis of 12 tumors reveals that 6 (50%) express exclusively the V beta 6 gene product, 2 (17%) are V beta 5+, and 1 (8%) each are V beta 8+ and V beta 9+. In normal C57BL/Ka mice, V beta 6 is expressed on 12%, V beta 5 is expressed on 9%, V beta 8 is expressed on 22%, and V beta 9 is expressed on 4% of TCRhi thymocytes. Thus, it appears that RadLV-induced thymic lymphomas are not randomly selected with respect to expressed TCR V beta type.     

The BM12 mutation and autoantibodies to dsDNA in NZB.H-2bm12 mice

Molecular and genetic tools have been used to shed light on the genes that contribute to susceptibility to murine lupus and the mechanisms that lead to immunopathology. The MHC genes and their products have been consistently shown to contribute toward the development of disease. To understand the contribution of MHC-class II genes, our laboratory had derived two inbred strains of mice, NZB.H-2bm12 and NZB.H-2b. These new colonies of mice were studied and compared in the 10th generation backcross; inbreeding was serially followed by H-2 typing, responses to beef/porcine insulin, and the presence of the B6 Ig allotype, IgG2ab. Of great interest is the finding that NZB.H-2bm12, in contrast to NZB.H-2b or NZB (H-2d), mice develop high titer autoantibodies to dsDNA. This result is unique because NZB (H-2d) mice, unliked NZB x NZW (NZB/W F1) or NZB x SWR (SNF1) hybrids do not develop autoantibodies to dsDNA, even after immunization. NZB mice, in contrast, are characterized only by autoantibodies to ssDNA. Our observation is also striking because the gene conversion that resulted in the I-A beta bm12 mutation occurred at amino acid residues 68, 71, and 72 of I-E beta b. Recently the contribution of NZW to accelerated autoimmunity in the NZB x NZW F1 hybrid has also been linked to H-2 and a single amino acid change at amino acid 72 of I-E beta. Thus, amino acid residue 72 may be a hot spot for disorders of immune regulation when superimposed on the appropriate genetic background. NZB mice expressing the I-Abm12 mutation will allow specific dissection of the requirements for autoantibody production to dsDNA uncomplicated by heterozygosity.     

Virus-specific CD8+ T-cell responses in mice transgenic for a T-cell receptor beta chain selected at random.

The consequences of severely limiting the T-cell receptor (TCR) repertoire available for the response to intranasal infection with an influenza A virus or with Sendai virus have been analyzed by using H-2k mice (TG8.1) transgenic for a TCR beta-chain gene (V beta 8.1D beta 2J beta 2.3C beta 2). Analyzing the prevalence of V beta 8.1+ CD8+ T cells in lymph node cultures from nontransgenic (non-TG) H-2k controls primed with either virus and then stimulated in vitro with the homologous virus or with anti-CD3 epsilon showed that this TCR is not normally selected from the CD8+ T-cell repertoire during these infections. However, the TG8.1 mice cleared both viruses and generated virus-specific effector cytotoxic T lymphocytes (CTL) and memory CTL precursors, though the responses were delayed compared with the non-TG controls. Depletion of the CD4+ T-cell subset had little effect on the course of influenza virus infection but substantially slowed the development of the Sendai virus-specific CTL response and virus elimination in both the TG8.1 and non-TG mice, indicating that CD4+ helpers are promoting the CD8+ T-cell response in the Sendai virus model. Even so, restricting the available T-cell repertoire to lymphocytes expressing a single TCR beta chain still allows sufficient TCR diversity for CD8+ T cells (acting in the presence or absence of the CD4+ subset) to limit infection with an influenza A virus and a parainfluenza type 1 virus.     

T cell tolerance to Mlsa encoded antigens in T cell receptor V beta 8.1 chain transgenic mice.

To study T cell tolerance, transgenic mice were generated that expressed the Mlsa-reactive T cell receptor (TCR) beta chain V beta 8.1 (cDNA) under the control of the H-2Kb promoter/immunoglobulin heavy chain enhancer on approximately 90% of peripheral T cells. In transgenic mice bearing Mlsa, thymocytes expressing the TCR at a high density were deleted and the percentage of Thy 1.2+ lymph node cells was reduced. The CD4/CD8 ratio of mature T cells was reversed in Mlsa and Mlsb transgenic mice independent of the H-2. RNA analysis and immunofluorescence with TCR V beta-specific antibodies revealed that expression of endogenous TCR beta genes was suppressed. Both Mlsa and Mlsb TCR beta chain transgenic mice mounted a T-cell-dependent IgG response against viral antigens, whereas the capacity to generate alloreactive and virus-specific cytotoxic T cells was impaired in TCR beta chain transgenic Mlsa, but not in transgenic Mlsb mice.