Surprisingly uneven distribution of the T cell receptor V beta repertoire in wild mice

Towards an integrated view of thymopoiesis

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

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

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

Allelic variations of human TCR V gene products

A central problem confronting the immune system is how to discriminate among vast numbers of antigens. Novel genetic ploys that aid the discriminative process, including complex gene rearrangements (in antibody and T-cell receptor (TCR) genes) and extensive allelic polymorphism (in major histocompatibility complex (MHC) genes), have been described. Recent evidence has suggested a further level of diversity; TCR V gene allelic variation. In this article David Posnett summarizes evidence in favour of this possibility and speculates on the possible functional consequences of TCR allelism.

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

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

Autoimmune diseases: the failure of self tolerance

The ability to discriminate between self and nonself antigens is vital to the functioning of the immune system as a specific defense against invading microorganisms. Failure of the immune system to "tolerate" self tissues can result in pathological autoimmune states leading to debilitating illness and sometimes death. The induction of autoimmunity involves genetic and environmental factors that have focused the attention of researchers on the trimolecular complex formed by major histocompatibility complex molecules, antigen, and T cell receptors. Detailed molecular characterization of these components points to potential strategies for disease intervention.

The staphylococcal enterotoxins and their relatives

Staphylococcal enterotoxins and a group of related proteins made by Streptococci cause food poisoning and shock in man and animals. These proteins share an ability to bind to human and mouse major histocompatibility complex proteins. The complex ligand so formed has specificity for a particular part of T cell receptors, V beta, and by engaging V beta can stimulate many T cells. It is likely that some or all of the pathological effects of these toxins are caused by their ability to activate quickly so many T cells. It is also possible that encounters with such toxins have caused mice, at least, to evolve mechanisms for varying their T cell V beta repertoires, such that they are less susceptible to attack by the toxins.

Polymorphism of Tcrb and Tcrg genes in Biozzi mice: segregation analysis of a new Tcrg haplotype with antibody responsiveness

Tcrb and Tcrg gene polymorphism was investigated in high (H) and low (L) responder Biozzi mice from selection I, II, and GS by Southern blot analysis with appropriate V and C probes. No polymorphism of the Tcrb haplotype was detected between H and L mice in all selections which were all found to be of the BALB/c type. The H-I and H-II g genotype was of BALB/c and DBA/2 type, respectively. In contrast, a new Tcrg haplotype shared by L-I and L-II mice was identified and characterized by C gamma 1, 2, 3, C gamma 4, V gamma 1, 2, 3, V gamma 5, and V gamma 6 restriction fragment length polymorphisms (RFLPs). Tcrg genotypes were not fixed in the GS selection and two additional new haplotypes were identified in two L-GS mice. An attempt was made to correlate the L-I g genotype with the low responder status by analyzing g haplotypes among highest and lowest responder (H-I X L-I)F2 hybrids immunized with sheep red blood cells (SRBC). No correlation was found in this segregation study, whereas a highly significant one was established with the H-2 haplotype, a locus already known to participate in the genetic control of H-I/L-I difference. The lack of correlation between SRBC response and the Tcrg genotype was consistent with the heterogenous g haplotypes found in mice of the GS selection. Together, the present results suggest that H and L mice have the same Tcrab potential repertoire and that T-cell receptor (Tcr) genes cannot be considered as immune response genes in this model. Our results also indicate that the F2 segregation analysis, given a polymorphic gene, is suitable for an investigation of its immune response functions.