Expression of a murine polyclonal T cell receptor marker correlates with the use of specific members of the V beta 8 gene segment subfamily

Alpha-galactosylceramide promotes killing of Listeria monocytogenes within the macrophage phagosome through invariant NKT-cell activation

alpha-Galactosylceramide (alpha-GalCer) has been exploited for the treatment of microbial infections. Although amelioration of infection by alpha-GalCer involves invariant natural killer T (iNKT)-cell activation, it remains to be determined whether macrophages (Mphi) participate in the control of microbial pathogens. In the present study, we examined the participation of Mphi in immune intervention in infection by alpha-GalCer using a murine model of listeriosis. Phagocytic and bactericidal activities of peritoneal Mphi from C57BL/6 mice, but not iNKT cell-deficient mice, were enhanced after intraperitoneal injection of alpha-GalCer despite the absence of iNKT cells in the peritoneal cavity. High levels of gamma interferon (IFN-gamma) and nitric oxide (NO) were detected in the peritoneal cavities of mice treated with alpha-GalCer and in culture supernatants of peritoneal Mphi from mice treated with alpha-GalCer, respectively. Although enhanced bactericidal activity of peritoneal Mphi by alpha-GalCer was abrogated by endogenous IFN-gamma neutralization, this was only marginally affected by NO inhibition. Similar results were obtained by using a listeriolysin O-deficient strain of Listeria monocytogenes. Moreover, respiratory burst in Mphi was increased after alpha-GalCer treatment. Our results suggest that amelioration of listeriosis by alpha-GalCer is, in part, caused by enhanced killing of L. monocytogenes within phagosomes of Mphi activated by IFN-gamma from iNKT cells residing in an organ(s) other than the peritoneal cavity.

Ly-49P activates NK-mediated lysis by recognizing H-2Dd

Little is known regarding the ligand specificity of Ly-49 activating receptor subfamily members expressed by NK cells. A new Ly-49 activating receptor related to Ly-49A in its extracellular domain, designated Ly-49P, was recently cloned from 129 strain mice. We independently cloned an apparent allele of Ly-49P expressed by nonobese diabetic and nonobese diabetes-resistant mouse strain NK cells. We found it to be reactive with the A1 Ab thought to recognize a polymorphic epitope expressed only by the Ly-49A inhibitory receptor of the C57BL/6 strain. Rat RNK-16 cells transfected with Ly-49P mediated reverse Ab-dependent cellular cytotoxicity of FcR-positive target cells, indicating that Ly-49P can activate NK-mediated lysis. We determined that RNK-16 lysis of Con A blasts induced by Ly-49P was MHC dependent, resulting in efficient lysis of H-2Dd-bearing targets. We found that the Dd alpha1/alpha2 domain is required for Ly-49P-mediated RNK-16 activation, as determined by exon shuffling and transfection. Thus, Ly-49P is the second activating Ly-49 receptor demonstrated to induce NK cytotoxicity by recognizing a class I MHC molecule.

Alanine scanning mutagenesis of an alphabeta T cell receptor: mapping the energy of antigen recognition

The T cell receptor (TCR) from the alloreactive T lymphocyte 2C recognizes a nonamer peptide QL9 complexed with the MHC class I molecule H2-Ld. Forty-two single-site alanine substitutions of the 2C TCR were analyzed for binding to QL9/Ld and anti-TCR antibodies. The results provided a detailed energy map of T cell antigen recognition and indicated that the pMHC and clonotypic antibody epitopes on the TCR were similar. Although residues in each Valpha and Vbeta CDR are important in binding pMHC, the most significant energy for the TCR/QL9/Ld interaction was contributed by CDRs 1 and 2 of both alpha and beta chains. The extent to which the individual energy contributions are directed at class I helices or peptide was also assessed.

Defective IgE production by SJL mice is linked to the absence of CD4+, NK1.1+ T cells that promptly produce interleukin 4

SJL mice produce little or no IgE in response to polyclonal stimulation with anti-IgD antibody and fail to express interleukin 4 (IL-4) mRNA in the spleen 5 days after injection of anti-IgD, in contrast to other mouse strains that produce substantial amounts of IgE and IL-4. Because IL-4 is critical in IgE production, the possibility that SJL mice are poor IgE producers because their naive T cells fail to differentiate into IL-4 producers must be seriously considered. IL-4 itself is the principal factor determining that naive T cells develop into IL-4 producers. A major source of IL-4 for such differentiation is a population of CD1-specific CD4+ T cells that express NK1.1. These cells produce IL-4 within 90 min of anti-CD3 injection. T cells from SJL mice fail to produce IL-4 in response to injection of anti-CD3. Similarly, SJL T cells and CD4+ thymocytes do not produce IL-4 in response to acute in vitro stimulation. SJL T cells show a marked deficiency in CD4+ cells that express the surface receptors associated with the NK1.1+ T-cell phenotype. This result indicates that the SJL defect in IgE and IL-4 production is associated with, and may be due to, the absence of the CD4+, NK1.1+ T-cell population.

The liver eliminates T cells undergoing antigen-triggered apoptosis in vivo

Deletion of mature peripheral T cells may result from TCR ligation by bacterial enterotoxins, endogenous provirus-encoded superantigens, and peptide antigens. But the ultimate fate of deleted T cells is not clear. Using a line of T cell receptor transgenic mice injected with antigenic peptide, we have documented that peripheral deletion is accompanied by the induction of abortive T cell activation followed by the disappearance of transgene-positive T cells. As these T cells disappear from the lymph nodes and spleen, they accumulate in the liver, where they undergo apoptosis. This is likely to be a general clearance pathway for T cells that are programmed to undergo apoptosis in vivo, and it may further explain the expansion of the intrahepatic T cell pool in mice with genetic defects in the T cell apoptosis mechanism, such as the lpr mutant.

A self-reactive class I-restricted T-cell response of H-2b mice to determinants of the V beta 8.2 domain of the T-cell receptor for antigen

We studied the induction of a self-reactive cytotoxic T lymphocyte (CTL) response to determinants of the variable V beta 8.2 region of the beta-chain of the T-cell receptor (TCR) for antigen in C57BL/6 (H-2b) mice. A CTL response was elicited in vivo by TCR peptide vaccination, and detected in vitro using syngeneic transfectants expressing a rearranged V beta 8.2+ TCR beta-chain. The first series of experiments used a 15-mer peptide representing residues 68-82 of the V beta 8.2 domain and containing Kb and Db allele-specific motifs. Immunization with this peptide stimulated an autoreactive CTL response that cross-reacted with V beta 8.2 epitopes presented by transfectants endogenously processing a V beta 8.2+ TCR beta-chain. These transfectants expressed a construct derived from a murine, rearranged V beta 8.2/D beta 2/J beta 2.3/C beta 2 TCR beta-chain cDNA. The V beta 8.2+ T-cell subset of peptide-primed mice was not deleted but its proliferative response to stimulation by the V beta 8.2-specific monoclonal antibody (mAb) F23.2 was suppressed. In a second series of experiments we immunized mice with a 23-mer peptide representing residues 41-63 of the V beta 8.2 domain that does not contain putative, allele-specific H-2b class I-restricted motifs. This TCR peptide vaccination stimulated a CD8+ CTL response reacting against syngeneic, peptide-pulsed targets but not cross-reacting against transfectants processing/presenting epitopes of the beta-chain. V beta 8.2+ T cells of these peptide-primed mice were not anergized. These data demonstrate that vaccination with an immunogenic peptide representing a naturally processed epitope of the V beta 8.2 domain of the TCR beta-chain induces a self-reactive CD8+ CTL specific for this V beta 8.2 epitope; and anergizes (but does not delete) V beta 8.2+ T cells.

T cell receptor (beta chain) transgenic mice have selective deficits in gamma delta T cell subpopulations

TCR-beta (T cell receptor-beta chain) transgenic mice have altered lymphocyte development. TCR-beta transgenic mice are hyporesponsive to alloantigens in vivo and are deficient in gamma delta T cells. In order to begin a study of the relationship between a deficiency of alloreactive gamma delta cells and the defective function of in vivo alloantigen recognition, we analysed the gamma delta T cell development in TCR-beta mice. The presence of the TCR-V beta 8.2 chain transgene is associated with inhibition of gamma chain gene rearrangement. In order to determine how the presence of the TCR-beta transgene affects gamma delta T cell development, gamma delta T cells were studied in the skin, intestine and spleen. TCR-beta mice have dramatically reduced numbers of gamma delta T cells in the spleen and moderately reduced numbers of gamma delta T cells among intestinal intraepithelial lymphocytes. In contrast, these mice have normal numbers of gamma delta dendritic epidermal cells (DEC). These selective deficits could be due to the developmental regulation of transgene transcription during fetal life. We examined transcription of the TCR-beta transgene in the fetal thymus and found that the TCR-beta transgene is first transcribed at high levels on day 16 of fetal life, after DEC have already migrated from the thymus to the epidermis. Furthermore, mRNA from the transgene was detected in DEC, ruling out the formal possibility that DEC bear a gamma delta receptor only because they are incapable of expressing the transgene.(ABSTRACT TRUNCATED AT 250 WORDS)

Vaccination with T cell receptor peptides primes anti-receptor cytotoxic T lymphocytes (CTL) and anergizes T cells specifically recognized by these CTL

We selected three peptides from the germ-line sequence of the V beta 8.2 and J beta 2.3 gene segments of the murine T cell receptor for antigen (TCR) which contained putative Kd- and Ld-restricted epitopes. Immunization of BALB/c (H-2d) mice with the V beta 8.2(67-90) 23-mer peptide 1 as well as the 15-mer V beta 8.2(95-108)-peptide 2 efficiently primed specific CD8+ cytotoxic T lymphocyte (CTL) responses in vivo against natural TCR-V beta 8.2 epitopes. V beta 8.2+ T cells were not deleted in TCR peptide-immunized mice because the fractions of V beta 8.2+ CD4+ and V beta 8.2+ CD8+ T cells in spleen and lymph nodes were not altered. The proliferative response of V beta 8.2+ T cells to stimulation by monoclonal antibody F23.2 was selectively suppressed (by 60-80%) in peptide-immunized BALB/c mice, indicating partial anergy of this T subset. Immunization of BALB/c mice with the J beta 2.3-derived peptide 3 stimulated a CD8+ CTL response against a class I-restricted epitope within this J beta segment that was also generated during natural "endogenous" processing of this self antigen. These data confirm the predictive value of major histocompatibility complex class I allele-specific motifs. The described experiments indicate that TCR peptide-primed CD8+ CTL recognize class I-restricted, natural V beta/J beta-TCR epitopes. Such anti-TCR CTL may, thus, operate in V beta-specific immunoregulation of the T cell system suppressing their functional reactivity without deleting them.

Specific prolongation of allograft survival by a T-cell-receptor-derived peptide

Allograft rejection results from the specific recognition by host CD8+ T cells of allogeneic major histocompatibility complex (MHC) molecules on the tissue graft. The specificity of this cellular response is determined by the molecular interaction of the T-cell receptor (TCR) on host T cells with the MHC molecule and its bound ligand on the grafted tissue. To better understand the precise manner by which the TCR interacts with the MHC-peptide complex and how to therapeutically intervene, we have studied the allogeneic response to the mouse class I MHC molecule Ld. In this report, the therapeutic potential of a synthetic peptide derived from the TCR V beta 8 variable region that predominates in responses to Ld was tested. This V beta 8-derived peptide was found to dramatically and specifically block the in vivo and in vitro allogeneic response to Ld. Furthermore, this specific blocking is not dependent upon the presence of V beta 8+ effector cells nor does the V beta 8 peptide bind to the Ld ligand binding cleft. We propose that this peptide functions as an antagonist, competing with the native TCR for recognition of the Ld molecule.

Constitutive tyrosine phosphorylation of the T-cell receptor (TCR) zeta subunit: regulation of TCR-associated protein tyrosine kinase activity by TCR zeta

The T-cell receptor (TCR) zeta subunit is an important component of the TCR complex, involved in signal transduction events following TCR engagement. In this study, we showed that the TCR zeta chain is constitutively tyrosine phosphorylated to similar extents in thymocytes and lymph node T cells. Approximately 35% of the tyrosine-phosphorylated TCR zeta (phospho zeta) precipitated from total cell lysates appeared to be surface associated. Furthermore, constitutive phosphorylation of TCR zeta in T cells occurred independently of antigen stimulation and did not require CD4 or CD8 coreceptor expression. In lymph node T cells that constitutively express tyrosine-phosphorylated TCR zeta, there was a direct correlation between surface TCR-associated protein tyrosine kinase (PTK) activity and expression of phospho zeta. TCR stimulation of these cells resulted in an increase in PTK activity that coprecipitated with the surface TCR complex and a corresponding increase in the levels of phospho zeta. TCR ligations also contributed to the detection of several additional phosphoproteins that coprecipitated with surface TCR complexes, including a 72-kDa tyrosine-phosphorylated protein. The presence of TCR-associated PTK activity also correlated with the binding of a 72-kDa protein, which became tyrosine phosphorylated in vitro kinase assays, to tyrosine phosphorylated TCR zeta. The cytoplasmic region of the TCR zeta chain was synthesized, tyrosine phosphorylated, and conjugated to Sepharose beads. Only tyrosine-phosphorylated, not nonphosphorylated, TCR zeta beads were capable of immunoprecipitating the 72-kDa protein from total cell lysates. This 72-kDa protein is likely the murine equivalent of human PTK ZAP-70, which has been shown to associate specifically with phospho zeta. These results suggest that TCR-associated PTK activity is regulated, at least in part, by the tyrosine phosphorylation status of TCR zeta.

Constitutive tyrosine phosphorylation of the T-cell receptor (TCR) zeta subunit: regulation of TCR-associated protein tyrosine kinase activity by TCR zeta

The T-cell receptor (TCR) zeta subunit is an important component of the TCR complex, involved in signal transduction events following TCR engagement. In this study, we showed that the TCR zeta chain is constitutively tyrosine phosphorylated to similar extents in thymocytes and lymph node T cells. Approximately 35% of the tyrosine-phosphorylated TCR zeta (phospho zeta) precipitated from total cell lysates appeared to be surface associated. Furthermore, constitutive phosphorylation of TCR zeta in T cells occurred independently of antigen stimulation and did not require CD4 or CD8 coreceptor expression. In lymph node T cells that constitutively express tyrosine-phosphorylated TCR zeta, there was a direct correlation between surface TCR-associated protein tyrosine kinase (PTK) activity and expression of phospho zeta. TCR stimulation of these cells resulted in an increase in PTK activity that coprecipitated with the surface TCR complex and a corresponding increase in the levels of phospho zeta. TCR ligations also contributed to the detection of several additional phosphoproteins that coprecipitated with surface TCR complexes, including a 72-kDa tyrosine-phosphorylated protein. The presence of TCR-associated PTK activity also correlated with the binding of a 72-kDa protein, which became tyrosine phosphorylated in vitro kinase assays, to tyrosine phosphorylated TCR zeta. The cytoplasmic region of the TCR zeta chain was synthesized, tyrosine phosphorylated, and conjugated to Sepharose beads. Only tyrosine-phosphorylated, not nonphosphorylated, TCR zeta beads were capable of immunoprecipitating the 72-kDa protein from total cell lysates. This 72-kDa protein is likely the murine equivalent of human PTK ZAP-70, which has been shown to associate specifically with phospho zeta. These results suggest that TCR-associated PTK activity is regulated, at least in part, by the tyrosine phosphorylation status of TCR zeta.

Irreversible suppression of CD8 expression in CD4-CD8+ thymocytes upon in vitro stimulation

CD8 (Ly-2) expression was suppressed in purified murine CD4-CD8+ thymocytes at the mRNA level upon continuous stimulation with PMA and ionomycin in the presence of rIL-2. The level of CD8 expression on CD4-CD8+ thymocytes was reduced gradually during the culture and a majority of them turned into CD4-CD8- cells after 48 hr. This suppression was not transient, since CD8 expression was not recovered on these cells in additional 48 hr of culture without PMA and ionomycin. The suppression was dependent on the concentrations of PMA and ionomycin, and inhibited by adding an immunosuppressant, CsA to the culture. Treatment with either PMA or ionomycin alone did not induce suppression of CD8. Crosslinking of CD3-epsilon chains also induced suppression of CD8 for a part of CD4-CD8+ thymocytes. Interestingly, CD8 expression was hardly suppressed in CD4-CD8+ peripheral T lymphocytes, suggesting that the mechanisms of suppression of CD8 is developmentally regulated. We propose that the suppression of CD8 expression at CD4-CD8+ stage involves an additional mechanism of negative selection of thymic T cells.

A bacterially expressed single-chain Fv construct from the 2B4 T-cell receptor

A single-chain Fv construct of the 2B4 T-cell receptor has been made and expressed in Escherichia coli as bacterial inclusion bodies. After solubilization in 6 M guanidine hydrochloride and formation of mixed disulfides with glutathione, the protein was refolded by diluting out the denaturant and allowing intramolecular disulfide bridges to form by disulfide exchange. Approximately 65-100 mg of refolded protein was obtained from 1 liter of bacterial culture, an appreciable fraction of which was monomeric in nondenaturing solvents. This protein bound to three monoclonal antibodies specific for allotypic or idiotypic determinants on the native 2B4 variable region but did not bind several other anti-T-cell-receptor monoclonal antibodies that lacked such specificity. These experiments show that T-cell-receptor variable regions, like the V regions of antibodies, can form a well-behaved single-chain Fv molecule and provide large amounts of recombinant single-chain Fv T-cell receptor that can be used to study T-cell function.

Disruption of CD8-dependent negative and positive selection of thymocytes is correlated with a decreased association between CD8 and the protein tyrosine kinase, p56lck

The CD4 and CD8 coreceptor molecules on immature thymocytes participate in T cell repertoire selection. To examine more definitively the role of CD4 and CD8 in the negative and positive selection of immature thymocytes, we generated transgenic mice with elevated surface CD4 expression and mated them with mice expressing a transgenic T cell receptor. Augmented CD4 expression was found to markedly alter CD8-dependent negative and positive selection of T cells specific for the male (H-Y) antigen presented by H-2Db major histocompatibility complex class I molecules. Moreover, the cytoplasmic tail of CD4 was essential for effecting these alterations, since the overexpression of tailless CD4 molecules failed to influence the outcome of CD8-dependent selection. The inhibition of positive and negative selection in double-transgenic mice expressing the full-length CD4 molecule was associated with a decreased interaction between the protein tyrosine kinase p56lck and CD8. These results strongly implicate p56lck in T cell repertoire selection.

Genetic dissection of T cell receptor V beta gene requirements for spontaneous murine diabetes

It has been demonstrated, in certain autoimmune disease models, that pathogenic T cells express antigen receptors of limited diversity. It has been suggested that the T cells responsible for the pathogenesis of type I diabetes mellitus might similarly demonstrate restricted T cell receptor (TCR) usage. Recently, attempts have been made to identify the V beta subset(s) that initiates and/or perpetuates the antiislet response in a mouse model of spontaneous autoimmune diabetes (non-obese diabetic [NOD] mice). In studies reported here, we have bred NOD mice to a mouse strain that congenitally lacks approximately one-half of the conventional TCR V beta alleles. Included in this deletion are TCR V beta gene products previously implicated as being involved in the pathogenesis of NOD disease. By studying second backcross-intercross animals, we were able to demonstrate that this deletion of TCR V beta gene segments did not prevent the development of insulitis or diabetes.

Peripheral selection of the T cell repertoire

T lymphocytes undergo selection events not only in the thymus, but also after they leave the thymus and reside in the periphery. Peripheral selection was found to be dependent on T cell receptor (TCR)-ligand interactions but to differ from thymic selection with regard to specificity and mechanism. Unlike thymic selection, peripheral selection required binding of antigen to the TCR, and it induced expansion of T cell clones. Tolerance to self antigens that are restricted to the periphery occurred through the elimination of self-reactive T cells and by the clonal anergy, which was associated with down-regulation of the alpha beta TCR and CD8.

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

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

Mutations in the major histocompatibility complex class I antigen-presenting groove affect both negative and positive selection of T cells

In several transgenic mouse models T cell development was shown to be controlled by the binding of the alpha/beta T cell receptor (TcR) to ligands in the thymus. In transgenic mice expressing a male-specific TcR alpha/beta, the presence of the restricting D major histocompatibility complex (MHC) molecule plus the male specific peptide deleted thymocytes at an early stage of development. On the other hand, maturation of T cells required an interaction of the TcR with the thymic D MHC molecules in the absence of specific peptides. This could imply that negative and positive selection of this receptor are affected differently by mutations in the HY peptide-binding groove of the D MHC molecule. Such mutants have been isolated and were shown to affect the response to HY antigen in that both the bm14 (residue Glu70----Asp) and the bm13 (residue Leu114----Glu, Phe116----Tyr and Glu119----Asp) strains do not normally mount cytotoxic responses to male cells. Here we show that these mutations affect antigenicity of male cells, as well as negative and positive selection of T cells in TcR alpha/beta transgenic mice.

Preferential usage of the V beta 8 gene family by CD4-CD8-T cell lines derived from spleen

Receptors encoded by the V beta 8 gene family and identified by the F23.1 antibody are commonly expressed amongst the CD4-CD8-T cell lines isolated from spleen cells infected in vitro with the RadLV retrovirus. All but one out of 12 cell lines showed between 50 and 85% F23.1+ cells in the uncloned cell population which is noticably higher than the approximately 13% level amongst the Ig- normal spleen cell population. There was a high frequency (approximately 50%) of F23.1+ clones from five of these cell lines. The frequency of F23.1 binding cells in the Ig-, CD4/CD8-depleted spleen population is only 0.2%, which gives a precursor frequency in spleen of less than 0.002%. This reflects selective isolation of CD4-CD8- alpha beta+ cells which express V beta 8 gene products by this culture scheme. The requirement for RadLV in induction of these cell lines has been established, suggesting that this retrovirus may selectively stimulate CD4-CD8-F23.1+ T cells. These cells may represent an autoimmune subset present in peripheral lymphoid tissue.

Characterization of V beta-bearing cells in athymic (nu/nu) mice suggests an extrathymic pathway for T cell differentiation

In the present article, the expression of the T cell receptor (TcR) beta chain and other T cell molecules was evaluated in surface immunoglobulin-negative spleen cell populations of young and old BALB/c and C57BL/6 nude mice, using a panel of monoclonal antibodies. The results obtained show that in young nude mice, most Thy-1high cells do not express other T cell markers. These mice have, however, a sizable population of Thy-1low cells with the same phenotype of alpha/beta+, CD4-CD8- thymocytes or MRL/lpr peripheral T cells, expressing predominantly genes of the V beta 8 family. The evolution of alpha/beta+ cells in aging nudes is strongly suggestive of an extrathymic pathway of differentiation of these cells since (a) the acquisition of high density TcR and CD3, as well as Thy-1 or CD4CD8 antigens at the cell surface of nude V beta+ T cells is not simultaneous; (b) alpha/beta+ cells in nude mice co-express other T cell markers at random and, even in old mice, they never completely resemble to the predominant high Thy-1+ CD3+ TcR alpha/beta+, CD4+CD8+ cells of euthymic controls; and (c) BALB/c nude T cells express V beta 11 genes, that are deleted in euthymic BALB/c mice. This latter finding may also indicate differences in the mechanisms of selection of T cells specificities in the thymus vs. the peripheral pools.

Immunohistology of T cell differentiation in the thymus of H-Y-specific T cell receptor alpha/beta transgenic mice

We examined the immunohistological aspects of the H-Y specific T cell receptor (TcR) alpha/beta transgene expression in the thymus of male and female transgenic (Tg) mice. Virtually all thymocytes expressed the beta transgene in both the male and female thymus. Expression of accessory molecules (co-receptors) in Tg mice deviated from control mice. In the male Tg thymus, CD8 expression was either low or absent on both cortical and medullary thymocytes. In contrast, in the thymus of female mice, CD8+ cells were found both in the cortex and in the medulla. The majority of medullary thymocytes was bright CD8+. This is in clear contrast to the CD8 distribution in control B6 mice, where only a few percent of medullary cells are CD8+. Similarly, the proportion of cells expressing CD4 antigens was reduced in the cortex and medulla of the thymus from male Tg mice, as compared to the thymus of female Tg mice and B6 control mice. Comparative analysis of the stromal cell types of the thymic microenvironments in the three groups of mice revealed that the cortical thymic microenvironment of male Tg mice differed, compared to that of female Tg mice. In particular, the deep cortex showed a closely packed meshwork of epithelial reticular cells. Moreover, H-2Db molecules (which are the restricting elements for the Tg TcR alpha/beta) were abnormally expressed in the thymic cortex of male mice. The cortical microenvironment in female mice, on the other hand, appeared normal. Together, the data indicate that TcR alpha/beta transgene expression in male mice leads to an aberrant co-receptor expression in both cortical and medullary lymphoid cells as well as an abnormal composition of the cortical microenvironment. Both phenomena may be the consequence of "negative selection" of developing H-Y-specific T cells, as it occurs only in the male Tg thymus. The absence of the H-Y antigen, but presence of the restricting element H-2Db in the thymic cortex of female mice, leads to accumulation of CD8+ in the medulla, a phenomenon interpreted as "positive selection".

Influence of non-major histocompatibility complex differences on the severity of lymphocytic choriomeningitis

The role of the non-major histocompatibility complex (MHC) genetic background in the development of lymphocytic choriomeningitis (LCM) was examined for a range of mouse strains of the H-2k haplotype. The onset of meningitis relative to the time of injection of LCM virus was delayed and the maximal level of cellular extravasation into cerebrospinal fluid was lower in C3H/HeJ and CBA/H compared with AKR/J, B10.Br and BALB/c.H-2k mice. Adoptive transfer experiments indicated that the C3H mice are genuine low responders, but immune spleen cells from the CBA/H were as potent on a cell-for-cell basis as those from the AKR/J. Further analysis with CBA/H, AKR/J and (CBA/H x AKR/J)F1 mice showed that the pattern of high response for the AKR/J was dominant, with the differential kinetics of the development of meningitis correlating with the cellularity of the cervical lymph nodes. Thus, the generation of the LCM inflammatory process is not dictated solely by the MHC phenotype.

Expression and sequences of T cell receptor beta-chain variable genes in the enlarged lymph nodes of C57BL/6-lpr/lpr mice

An autosomal recessive gene, lpr, is responsible for lymphoproliferation and autoimmunity of lpr-mice, in which background genes are also known to influence the development of autoimmune disease. To define the differences in abnormally proliferating T cells between C57BL/6-lpr/lpr and MRL/Mp-lpr/lpr mice, and to try and understand the influence of background in the differing expression of autoimmune disease in both strains, we analysed the sequences of T cell antigen receptor V beta genes expressed in the cells from the enlarged lymph nodes of C57BL/6-lpr/lpr mice. Eleven beta cDNAs out of the 38 C beta-specific cDNAs contained sequences with open reading frames from the beginning of the variable region to the expected termination codons at the end of the constant regions. Notably, 36% of the functional beta-chain mRNAs expressed V beta 8.3 genes, whereas V beta 8.1 and V beta 8.2 genes were not found. These results are consistent with a relatively lower frequency of the V beta 8.1 or V beta 8.2 expressing cells in the hypertrophic lymph nodes of C57BL/6-lpr/lpr mice, detected by KJ16-133 monoclonal antibody. Interestingly, other V beta genes expressed in these mice were completely distinct from those in MRL/Mp-lpr/lpr mice as described by Singer et al. (1986). The different distribution of V beta genes expressed in C57BL/6-lpr/lpr from that in MRL/Mp-lpr/lpr mice might be related to the differences in the genetic background and the expression of lpr gene-associated autoimmunity.

Antigen-specific helper function of cell-free T cell products bearing TCR V beta 8 determinants

Although the T cell receptor (TCR) alpha beta heterodimer and its encoding genes have been characterized, a cell-free form of this receptor, which is needed for the study of functional or ligand-binding properties of the receptor, has not previously been isolated. When the cell-free supernatant products of activated cloned T helper (TH) cells were found to mediate helper activity with antigen specificity identical to that of intact T cells, experiments were carried out to determine whether this functional activity was mediated by a cell-free form of TCR-related material. A disulfide-linked dimer indistinguishable from the T cell surface alpha beta heterodimer was precipitated from cell-free supernatants of cloned TH cells with F23.1, a monoclonal antibody specific for a TCR V beta 8 determinant. Moreover, when cell-free TH products were bound to and eluted from immobilized F23.1, these affinity-purified materials had antigen-specific and major histocompatibility complex-restricted helper activity that synergized with recombinant lymphokines in the generation of B cell antibody responses. These findings suggest that the factor isolated from T cell supernatants is a cell-free form of the TCR alpha beta dimer.

Activation of gamma delta T cells in the primary immune response to Mycobacterium tuberculosis

Although the immunologic role of T cells bearing the conventional alpha beta T cell receptor (TCR) has been well characterized, little is known about the function of the population of T cells bearing the gamma delta TCR. Therefore, the role of gamma delta T cells in the immune response to Mycobacterium tuberculosis (MT) was investigated. The number of TCR gamma delta cells in the draining lymph nodes of mice immunized with MT was greatly increased in comparison with the number of TCR alpha beta cells. Three biochemically distinct gamma delta TCRs were detected. Analyses of cell cycle, of interleukin-2 receptor expression, and of interleukin-2 responsiveness showed that a large proportion of the gamma delta T cells were activated in vivo. TCR gamma delta cells responded to solubilized MT antigens in vitro but, in contrast to MT-specific alpha beta T cells, the response of gamma delta T cells to MT did not require major histocompatability complex class II recognition. These results provide an example of antigen-specific activation of gamma delta T cells in vivo and indicate that gamma delta T cells may have a distinct role in generating a primary immune response to certain microorganisms.

Relative V beta transcript levels in thymus and peripheral lymphoid tissues from various mouse strains. Inverse correlation of I-E and Mls expression with relative abundance of several V beta transcripts in peripheral lymphoid tissues

We have measured the relative levels of transcripts for 15 of the 22 known V beta gene segments. The level of transcripts for the highest and lowest expressed V beta gene segment differed by greater than 20-fold in the thymus and an even larger difference was observed in the periphery. The levels of expressions were unrelated to the order of the V beta genes on the chromosome. For most of the V beta gene segments, the relative transcript levels were the same in the thymus and periphery, suggesting that thymic selection in general does not act solely upon the V beta gene segment. One V beta gene segment in the BALB and B10 mice strains was an exception to this rule. V beta 5.2 expression in the periphery of BALB and B10 mice inversely correlated with the expression of the MHC class II molecule I-E. Five V beta gene segments had reduced transcript levels in the periphery of Mls-1a mice compared with their thymic levels or to the levels found in Mls-1b mice. The peripheral level of V beta 3 transcripts vary with MHC and Mls-2 haplotypes. The observation that certain V beta transcript levels are reduced in the periphery when compared with the thymus favors the hypothesis that self tolerance at the T cell level results in the elimination of self-reactive T cells, rather than paralysis by a block at some post-transcriptional step. Finally, the wide variability of V beta gene segment expression in the thymus suggests mechanisms exist to import an early bias to the repertoire. Whether this bias results from differential V beta segment rearrangement rates, differential V beta expression rates, or events occurring after TCR-alpha/beta expression on immature/nonmature thymocyte cell surfaces is yet to be determined.

TCR3: a third T-cell receptor in the chicken

Avian homologues of mammalian gamma delta and alpha beta T-cell antigen receptors, TCR1 and TCR2, have been identified with monoclonal antibodies. These TCR isotypes are associated with the avian CD3 proteins on the T-cell surface. During chick development, T-cell subpopulations bearing CD3/TCR1 or CD3/TCR2 receptor complexes are generated sequentially in the thymus and seeded to the periphery in the same order. In this study, we used two-color immunofluorescence to identify the subsequent development of a third subpopulation of T cells, provisionally named TCR3. These CD3+ cells, which expressed neither TCR1 nor TCR2, were first detected in the blood 1 week after hatching and increased numerically as a function of age to account for approximately 15% of the circulating T-cell pool in adults. Most (greater than 80%) of the TCR3 cells expressed the CD4 accessory molecule. The relative incidence of the TCR3 subpopulation increased dramatically as a consequence of embryonic treatment with anti-TCR2 antibody and thymectomy after hatching. Two disulfide-linked polypeptides, of Mr 48,000 and 40,000, were associated with the CD3 complex on the TCR3 cells. Examination of the TCR protein backbones and peptide mapping of the TCR chains after partial proteolysis indicated that the TCR3 heterodimer differs from both TCR1 and TCR2. These results suggest the existence of a third class of T-cell receptors in birds.

Identification of T-cell receptor V beta deletion mutant mouse strain AU/ssJ (H-2q) which is resistant to collagen-induced arthritis

Our laboratory is involved in investigating the role of T-cell receptor (Tcr) in collagen-induced arthritis (CIA). During these studies we found AU/ssJ (H-2q) mice to be resistant to CIA like SWR (H-2q), as compared with other H-2q strains with wild-type Tcr like DBA/1 and B10.Q. Upon screening with monoclonal antibodies F23.1 and KJ23a, AU/ssJ was found to be F23.1 negative (V beta 8 Tcr negative) and KJ23a positive (V beta 17a Tcr positive). Southern blot analysis on liver DNA using specific Tcr-V beta probes confirmed the deletion of V beta 8 gene family and also showed that AU/ssJ mice have deletions of V beta 9, V beta 13, V beta 12, and V beta 11 genes of Tcr. Further, these mice show a restriction fragment length polymorphism pattern with V beta 10, V beta 6, and V beta 17 probes similar to SWR mice as compared with B10 mice. Since SWR and AU/ssJ are from different backgrounds, these studies indicate that specific variable region beta chain genes of Tcr are crucial for susceptibility to CIA in mice. Furthermore, these studies identify an additional inbred strain which has also deleted 50% of its Tcr-V beta genes.

Deletion of autospecific T cells in T cell receptor (TCR) transgenic mice spares cells with normal TCR levels and low levels of CD8 molecules

Transgenic mice that carry on a large fraction of their T cells an alpha/beta T cell receptor that recognizes the male antigen in the context of H-2Db molecules were constructed. An mAb specific for the transgenic receptor was developed and used to analyze T cell subsets in male transgenic H-2b mice. The vast majority of immature CD4+8+ T cells that express the transgenic TCR were deleted in the male transgenic mouse. Nevertheless, the majority of T cells spared by this deletion process expressed a high level of the transgenic TCR. These T cells, however, had an abnormal CD4/CD8 phenotype in that they expressed either no CD8 molecules or only low levels.

T-cell receptor-specific monoclonal antibodies against a V beta 11-positive mouse T-cell clone

Two monoclonal antibodies specific for the mouse T-cell receptor (Tcr) have been established by immunization with a V beta 11+ T-cell clone, clone C6. One is a rat antibody, KT11 (IgG2b, k), specific for the V beta chain of C6, V beta 11. This was demonstrated by the fact that the strain distribution pattern of KT11+ cells was similar to that of V beta 5, 8, 9, 11, 12, and 13 and that the gene that encodes the molecule detected by KT11 was closely linked to V beta 8 in (B10 X SJL)F1 X SJL backcross mice. Furthermore, V beta of C6 has been cloned from a lambda gt10 cDNA library and was demonstrated to be identical to the V beta 11 published sequences. All strains of mice that do not express major histocompatibility complex class II E molecules had higher numbers of KT11+ cells than E+ strains. The KT11+ population in A strain mice and its H-2 congenic strains, however, was not affected by the presence or absence of E molecules. The other is a mouse antibody, KTL2 (IgM), specific for the idiotope of the Tcr expressed on the clone C6. Both antibodies were mitogenic and induced cytotoxicity. Expression of epitopes detected by KT11 or KTL2 was down-modulated by a T3 epsilon-specific antibody 145-2C11.

Thymic selection process induced by hybrid antibodies

Thymus-derived (T) lymphocytes using the alpha beta T-cell antigen receptor (TCR) recognize fragmented antigen in conjunction with surface molecules encoded by genes of the major histocompatibility complex (MHC). Peripheral T lymphocytes preferentially see antigen presented by self rather than by foreign MHC molecules, and autoreactive T lymphocytes are deleted. Thus, the peripheral T-lymphocyte repertoire is skewed towards recognition of antigen in the context of self-MHC and towards tolerance to self-antigens. During T-lymphocyte development in the thymus, this repertoire is formed by the interaction of TCR with MHC molecules resulting in positive and negative selection phenomena. Hybrid antibodies (HAbs) that carry binding sites to the TCR and to a surface marker on another cell can engage all T lymphocytes regardless of their specificity. It should be possible to mimic selection processes in normal animals with HAb that specifically link members of a TCR family to MHC molecules on the thymic stroma. We have probed T-lymphocyte development with HAbs linking V beta 8-positive TCR to either class I or class II MHC products in thymic organ culture. Thymocytes exposed to either HAb in an early stage of maturation respond with a significant increase in the frequency of V beta 8-carrying cells. At a later stage of development V beta 8-positive thymocytes are depleted. These results illustrate the succession of positive and negative selection in the developing thymus of normal mice.

Demethylated CD8 gene in CD4+ T cells suggests that CD4+ cells develop from CD8+ precursors

Mature T cells and medullary thymocytes bear either the CD4 or CD8 differentiation antigen. Precursor cells in the thymus express neither CD4 nor CD8 (CD4-8-), but most cortical thymocytes are CD4+8+. Whether CD4+ and CD8+ mature T cells arise directly from CD4-8- precursors or from a CD4+8+ intermediate remains unresolved. In this study, methylation of the CD8 gene in murine T cells and thymocytes was examined. There was progressive demethylation of the CD8 gene in the thymus during the transition from CD4-8- to CD4+8+. A similar pattern of demethylation of the CD8 gene was seen in CD4+ mature T cells, suggesting previous expression of CD8 in the CD4+ lineage.

Deletion of self-reactive T cells before entry into the thymus medulla

The thymus is important in the differentiation of bone marrow-derived precursor cells into functional T cells; humoral factors, as well as physical interactions with nurse cells, dendritic cells and epithelial cells, are thought to be instrumental in this process. Thymic lymphocytes mature during their migration from the cortical to the medullary region of the thymus, when they undergo phenotypic changes that include the acquisitions of T-cell antigen receptors, hormone receptors and differentiation antigens. Cortical T cells are thus mostly CD4+CD8+, whereas medullary T cells are either CD4+CD8- or CD4-CD8+. During this period T cells are subjected to two types of repertoire selection: all T cells recognizing self-MHC with low affinity may be preferentially amplified (positive selection), and in a second step T cells with high-affinity receptors for self-MHC determinants plus self antigens are eliminated (negative selection). We have described two monoclonal antibodies specific for the V beta 6 gene segment of the alpha/beta heterodimeric T-cell antigen receptor and have shown that most CD4+/V beta 6+ T cell recognize the Mlsa antigenic determinant but not Mlsb; similar results have been reported for V beta 8.1 and Mlsa. In both situations, tolerance to Mlsa correlated in an MHC-dependent fashion with absence of V beta 6 or V beta 8.1 T-cell antigen receptor expressing T cells in the periphery. We show here by immunostaining of thymus cryosections and cytofluorometric analysis that V beta 6-expressing cortical T cells are present at high density in both Mlsa and Mlsb mice, but do not enter the medullary region of Mlsa animals.

Positive and negative selection of an antigen receptor on T cells in transgenic mice

The T-cell repertoire found in the periphery is thought to be shaped by two developmental events in the thymus that involve the antigen receptors of T lymphocytes. First, interactions between T cells and major histocompatibility complex (MHC) molecules select a T-cell repertoire skewed towards recognition of antigens in the context of self-MHC molecules. In addition, T cells that react strongly to self-MHC molecules are eliminated by a process called self-tolerance. We have recently described transgenic mice expressing the alpha beta T-cell receptor from the cytotoxic T lymphocyte 2C (ref. 11). The clone 2C was derived from a BALB.B (H-2b) anti-BALB/c (H-2d) mixed lymphocyte culture and is specific for the Ld class I MHC antigen. In transgenic H-2b mice, a large fraction of T cells in the periphery expressed the 2C T-cell receptor. These T cells were predominantly CD4-CD8+ and were able to specifically lyse target cells bearing Ld. We now report that in the periphery of transgenic mice expressing Ld, functional T cells bearing the 2C T-cell receptor were deleted. This elimination of autoreactive T cells appears to take place at or before the CD4+CD8+ stage in thymocyte development. In addition, we report that in H-2s mice, a non-autoreactive target haplotype, large numbers of CD8+ T cells bearing the 2C T-cell receptor were not found, providing strong evidence for the positive selection of the 2C T-cell receptor specificity by H-2b molecules.

Two monoclonal rat antibodies with specificity for the beta-chain variable region V beta 6 of the murine T-cell receptor

Two rat monoclonal antibodies (mAbs), 44-22-1 and 46-6B5, which recognize an alloreactive cytotoxic clone, 3F9, have been further tested on a panel of T hybridomas and cytotoxic T-cell clones for binding and functional activities. The mAbs recognized only those cells sharing the expression of the T-cell receptor beta-chain variable region gene V beta 6 with 3F9. All V beta 6+ cells were activated by these mAbs under cross-linking conditions and their antigen-specific activation was blocked by soluble mAb. Furthermore, depletion of 46-6B5+ normal lymph node T cells eliminated all cells expressing the epitope recognized by 44-22-1 and V beta 6 mRNA.

Selective expression of an antigen receptor on CD8-bearing T lymphocytes in transgenic mice

The major problem in the study of T-cell development is that of tracking thymocytes of a given specificity. Recent studies have exploited natural correlations between the expression of a particular V beta gene segment and T-cell receptor (TCR) specificity. We and others (refs 5, 6 and M. Davis, personal communication) have taken an alternative approach. We have generated transgenic mice expressing the alpha beta antigen receptor from the cytotoxic T-lymphocyte clone 2C (ref. 7). In transgenic mice of the same haplotype as the 2C clone, the 2C TCR was expressed on 20-95% of peripheral T cells. Very few of these T cells carried the CD4 antigen; the vast majority were CD4-CD8+ and were able to lyse targets with the same specificity as the original 2C clone. These results indicate that the alpha beta heterodimer transfers specificity to recipient cells as expected from earlier studies, and that receptor specificity in T-cell repertoire selection is determined by both alpha beta heterodimer and CD4 or CD8 accessory molecules.

Intrathymic deletion of self-reactive cells prevented by neonatal anti-CD4 antibody treatment

T-cell differentiation in the thymus involves the coordinate expression of genes encoding the alpha and beta chains of the major histocompatibility complex-restricted heterodimeric antigen receptor (TCR) complex, as well as other functionally important molecules such as CD4 and CD8. The repertoire of TCR expressed by T cells is generally thought to be influenced by positive and/or negative selection events occurring when TCRs on developing T cells interact with self-antigens and major histocompatibility complex components. Using a model system in which specific antigen-reactive cells can be monitored by virtue of their preferential expression of certain TCR beta-chain variable (V beta) domains, it has been shown that self-reactive T cells are clonally deleted during development. We report here that clonal deletion of V+ beta 6 cells in Mlsa mice can be prevented by in vivo neonatal administration of monoclonal antibodies directed against CD4. Furthermore, as anti-CD4 monoclonal antibody treatment resulted in the reappearance of V+ beta 6 cells in the mature CD8+ T-cell subset, it is likely that clonal deletion acts on the CD4+CD8+ thymocyte subset and that this subset is an intermediate stage in the differentiation pathway of both CD4+ and CD8+ T-cell lineages.

Multiple discrete encephalitogenic epitopes of the autoantigen myelin basic protein include a determinant for I-E class II-restricted T cells

Immunization with the autoantigen myelin basic protein (MBP) causes experimental allergic encephalomyelitis (EAE). Initial investigations indicated that encephalitogenic murine determinants of MBP were located only within MBP 1-37 and MBP 89-169. Encephalitogenic T cell epitopes within these fragments have been identified. Each epitope is recognized by T cells in association with separate allelic I-A molecules. A hybrid I-E-restricted T cell clone that recognizes intact mouse (self) MBP has been examined. The epitope recognized by this clone includes MBP residues 35-47. When tested in vivo, p35-47 causes EAE. T cell recognition of p35-47 occurs only in association with I-E molecules. These results provide the first clear example that antigen-specific T cells restricted by I-E class II molecules participate in murine autoimmune disease. Furthermore, it is clear that there are multiple (at least three) discrete encephalitogenic T cell epitopes of this autoantigen, each recognized in association with separate allelic class II molecules. These results may be relevant to human autoimmune diseases whose susceptibility is associated with more than one HLA-D molecule.

The V beta 8 gene family is preferentially used by 'naturally' activated T cells

Receptors encoded by the V beta 8 gene family detected by the monoclonal antibody F23.1 are expressed among 'naturally' activated T cells in normal spleen at frequencies significantly higher than in the total CD4+ and CD8+ cell populations. The positive selection of these clones into 'natural' T-cell activity could be the reason for the high frequencies of cells expressing V beta 8 genes. This phenotype is strain-dependent.

Development of autoreactive L3T4+ T cells from double-negative (L3T4-/Ly-2-) Thy-1+ spleen cells of normal mice

Thy-1+/L3T4-/Ly-2- spleen cells were purified from normal C57BL/6 (B6) and C,B-17 mice. Cells within this subset expressed the T cell receptor (TcR) for antigen: the majority of cells in this subset were CD3+; a fraction of the cells was stained with the monoclonal antibody (mAb) F23.1; and the TcR molecule was immunoprecipitable with mAb F23.1 from cells within this subset. In limiting dilution analyses, about 1/30 cells within this subset were growth inducible in vitro by stimulation with phorbol myristate acetate (PMA) plus ionomycin; conditioned media containing interleukin (IL) 1, IL2, IL3 or IL4 activity neither triggered nor promoted in vitro growth of these cells. The in vitro generated T cells displayed the Thy-1+/L3T4+/Ly-2- surface phenotype and were self-reactive, i.e., proliferated preferentially in response to syngeneic stimulator cells, and secreted IL2 and IL3 only in response to syngeneic but not allogeneic stimulator cells. The proliferative response of these cells to syngeneic stimulator cells was blocked by anti-self Ia mAb. This autoreactive helper T cell subset was not inducible in purified Thy-1+ spleen cell subsets from athymic nude mice or scid mice. Autoreactive helper T cells did not express detectable levels of the IL2 receptor (IL2R), and their proliferative response was not blocked by anti-IL2R mAb. From PMA plus ionomycin-stimulated double-negative Thy-1+ spleen cells, 14 T cell clones were established in long-term culture which displayed the CD3+CD4+CD8- surface phenotype and were self-reactive.

The specificity of the interaction between the agretope of an antigen and an Ia-molecule can depend on the T cell clonotype

A series of T cell clones was developed from (B10 x B10.BR)F1 mice immunized with the isolated A chain of pig insulin. The T cell clones show considerable diversity as defined by their distinct reactivities to pig, beef, sheep and horse insulins in combination with the same syngeneic Ab alpha Ak beta molecules. These species variants of insulin differ from each other only in amino acid residues in position A8, A9 or A10 within the so-called A chain loop and responsiveness of mice to these variants is under Ir gene control. A detailed analysis of the stimulatory capacity of various insulin/Ia combinations including inhibition experiments with anti-Ia- and -L3T4 antibodies led to the following interpretation: the amino acid residues A8-A10 are involved in the interaction of the insulin A chain with the Ia molecules. This region can, therefore, be regarded as part of the agretope. Structural variations within this region can modify the stimulatory potency of the insulin variants. However, whether a particular amino acid substitution results in an enhancement or a reduction of the response depends on the fine specificity of the T cell clone involved. Thus, an interaction of Ia molecules with antigen cannot solely account for the functional specificity of an agretope, rather this also depends on the structure of the particular T cell receptor that participates in recognition.

Expression of the gamma-delta T-cell receptor on intestinal CD8+ intraepithelial lymphocytes

The vast majority of mature T lymphocytes in the peripheral blood and lymphoid organs use the CD3-associated alpha, beta T-cell receptor (TCR) heterodimer for antigen recognition. A second class of TCRs consists of disulphide-linked gamma and delta proteins that are also CD3-associated. A subset of early CD3+ fetal and adult CD4- 8- thymocytes express gamma, delta TCRs before alpha, beta TCRs are detectable. In addition, a minor (1-5%) subpopulation of peripheral T lymphocytes, and some spleen cells from nude mice express gamma, delta TCRs. Notably, dendritic epidermal cells have also been shown to express gamma, delta TCRs. All of these populations lack CD4 and CD8 molecules. We now report that most mature T cells residing in the murine intestinal epithelium express CD3-associated TCRs composed of gamma-chains disulphide-linked to a protein resembling the delta-chain. The striking feature of these intraepithelial lymphocytes (IEL) was that they were exclusively CD4-8+. In addition, approximately half of CD3-bearing IEL lacked detectable Thy-1 on the cell surface, which is unprecedented for murine T cells. In contrast to other CD8+ peripheral T cells, freshly isolated IEL could be induced to display cytolytic activity by engaging the CD3 molecule, indicating that activation had occurred in vivo. Thus, CD8+ IEL are a phenotypically diverse and anatomically restricted population of lymphocytes that use gamma-chain containing heterodimers for antigen recognition.

Predominant expression of a T cell receptor V beta gene subfamily in autoimmune encephalomyelitis

TCR beta chain gene expression of individual T cell clones that share the same MHC class II restriction and similar fine specificity for the encephalitogenic NH2 terminus of the autoantigen myelin basic protein (MBP) has been examined. TCR V beta expression was examined by FACS analysis with mAbs specific for the V beta 8 subfamily of TCR beta chain genes. 14 of 18 (78%) NH2-terminal MBP-specific clones examined express a member of the TCR V beta 8 subfamily. Southern analysis was used to identify which member(s) of the TCR V beta 8 subfamily is expressed by these clones. Each of four clones examined uses V beta 8.2, though two different V beta 8.2-J beta 2 combinations were identified. Our findings indicate that there is restricted TCR V beta usage in the autoimmune T cell response to the dominant encephalitogenic NH2-terminal epitope of the MBP. The use of an mAb to the antigen-specific TCR in the prevention of T cell-mediated autoimmune disease has been investigated. Our results demonstrate that in vivo administration of a TCR V beta 8-specific mAb prevents induction of autoimmune encephalomyelitis.

In transgenic mice the introduced functional T cell receptor beta gene prevents expression of endogenous beta genes

Transgenic mice were constructed with a functional T cell receptor beta gene. Transcription of the introduced gene is largely confined to T cells, but low levels of transcripts are also seen in B cells and in other tissues. Serological analyses show that most, if not all, of the T lymphocytes express the transgenic beta chain on the cell surface and lack beta chains encoded by endogenous beta genes. Molecular genetic analyses of uncloned and cloned T lymphocytes demonstrate that rearrangement of endogenous beta genes is incomplete. Partial D beta 1-J beta 1 rearrangements are found preferentially, while complete VDJ rearrangements are not seen. These findings show that expression of the transgene regulates the rearrangement of endogenous beta genes. Although the alpha beta T cell receptors of the transgenic mice are homogeneous with respect to the beta chain, they are fully functional, at least in a variety of allogeneic responses.

T-cell receptor V beta use predicts reactivity and tolerance to Mlsa-encoded antigens

T lymphocytes reactive with the product of the Mlsa-allele of the minor lymphocyte stimulating (Mls) locus use a predominant T-cell receptor beta-chain variable gene segment (V beta 6). Such V beta 6-bearing T cells are selectively eliminated in the thymus of Mlsa-bearing mice, consistent with a model in which tolerance to self antigens is achieved by clonal deletion.

Self-tolerance eliminates T cells specific for Mls-modified products of the major histocompatibility complex

In mice the product of the Mlsa locus is an unusual antigen capable of interaction with certain products of the major histocompatibility locus (MHC) to form a ligand for a large portion of the T-cell alpha/beta receptor repertoire, including nearly all receptors that use V beta 8.1. The presence of Mlsa/MHC during T-cell development results in the deletion of T cells that express V beta 8.1, documenting the importance of clonal deletion in establishing tolerance to self antigens.

Possible role of V beta T cell receptor genes in susceptibility to collagen-induced arthritis in mice

Arthritis was induced by immunization of type II collagen in adjuvant in mice from H-2q-bearing crosses between SWR (H-2q/q) and B10 (H-2b/b mice), two strains known to be resistant to collagen-induced arthritis (CIA). The resistance of B10 is known to be due to its MHC haplotype, but it was postulated that the resistance of SWR mice which expresses the susceptible MHC haplotype could be due to the deletion of close to 50% of the V beta genes of the T cell receptor (TCR) in them. 17% of the F1 hybrids, 33% of the SWR backcrosses, 68% of the B10 backcrosses, and 52% of the F2 hybrids developed arthritis on follow-up to 5 mo after primary immunization with collagen. There was no significant difference in anti-type II collagen antibody titers between the arthritic and nonarthritic mice in each of these crosses. The segregation of the TCR genes with arthritis was determined in the F2 population by typing with F23.1 mAb that reacts with T cells using V beta 8 subfamily genes in their TCRs. SWR mice are F23.1- as V beta 8 genes are deleted in them. All six of arthritic mice homozygous for H-2q, and thus with an H-2 haplotype similar to SWR mice, expressed the F23.1 marker. These studies indicate that for complete susceptibility to collagen-induced arthritis, not only is a susceptible MHC haplotype (H-2q) important, but possibly also the presence of a subset of T cells using certain specific V beta genes in their TCRs. Other background genes may, however, modulate the severity of arthritis.