We have examined the T cell receptor (TcR) expression of clones specific for epitopes of mycobacterial 65-kDa heat-shock protein (hsp65) in the context of two different HLA molecules, and used this system as a model to assess the selection of T cells responsive to this antigen in vivo. DR3-restricted clones were raised from both the synovial fluid (SF) and peripheral blood (PB) of a patient with reactive arthritis in three separate cloning events. Five of five SF-derived clones tested expressed either V beta 5.2 or a closely related beta chain, V beta 5.6. The alpha chains expressed by V beta 5.2+ and V beta 5.6+ clones were from different families, V alpha 2.4 and V alpha 23.2, respectively. Nine of ten clones derived from two cloning procedures on PB taken 3 years later also expressed either V beta 5.2 or V beta 5.6. This suggests that the TcR repertoire for recognizing this major histocompatibility complex/peptide complex is relatively restricted and favors the use of V beta 5. Conservation of the beta chain third complementarity-determining region (CDR3) sequence was not evident, however. Sequencing alpha and beta chains of representative V beta 5.2+ and V beta 5.6+ PB-derived clones revealed TcR which were identical to those utilized by the SF-derived clones, showing that the repertoire for recognition of this antigen is stable over time. Similar studies of TcR expression were carried out on hsp65-specific, DP4-restricted clones derived from the SF of a patient with rheumatoid arthritis by two independent cloning procedures. There was conservation of alpha chain usage, since all clones expressed a member of the V alpha 1 family, but again CDR3 sequence conservation was not apparent. beta chain usage was not restricted since different clones expressed V beta 6.7, V beta 22.3 and V beta 12. Subtle differences in epitope specificity were detected for two clones with differing TcR. Once more, T cell clones with identical alpha and beta TcR chains were obtained from the separate cloning procedures, suggesting oligoclonalty of T cells with this defined specificity in the patient's SF.

The variation of the alpha beta T cell receptor (TCR) results mainly from rearrangements of germ-line V, D and J elements combined with the processes of N- and P-region addition. In addition to this extensive diversity, diallelic polymorphism is also recognized in V regions of beta loci. Four such polymorphisms have previously been defined, but the full extent of such variation has not yet been established. To investigate allelic polymorphism, we used a strategy based V locus-specific polymerase chain reaction and single-strand conformation polymorphisms. Studying the two V beta 2 loci and the V alpha 8.1 locus, we found that all exhibited a coding polymorphism. One of the V beta 2 loci proved to be the first multiallele segment to be recognized, with three common variants. The second V beta 2 locus, for which none of the two alleles has been identified in cDNA, appeared in fact to be a V beta orphon, in abnormal location on the chromosome 9. A yeast artificial chromosome containing part of the TCRB locus allowed us to place the first V beta 2 segment on the known map to define haplotypes with two other polymorphic segments: V beta 1 and V beta 6.7. Multiple distinct haplotypes result from combinations between these polymorphic loci, showing that V beta regions are highly variable between individuals. Two alleles exist at the V alpha 8.1 segment and both are expressed. This represents the first example of a frequent coding polymorphism for TCRA gene. The distribution of allele frequencies for these segments suggest the action of balancing selection. These data add a further dimension to TCR polymorphism and suggest new candidates to explore TCR-encoded susceptibility to autoimmune diseases.

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