Analysis of sheep T-cell receptor beta-chain heterogeneity.

We analyzed nucleotide and deduced amino acid sequence heterogeneity of sheep T-cell receptor beta-chain cDNAs isolated from an anchored-polymerase chain reaction library. Evaluation of 34 individual rearrangements has defined 18 new beta-chain variable region sequences which have been clustered into 13 families. Presumptive allelic polymorphisms of four of these variable regions have been defined, as well as ten distinct beta-chain joining region sequences. The present analysis indicates that sheep T-cell receptor beta-chains are composed of characteristic leader, variable, joining, and constant region sequences, and that imprecise joining and N-region addition contribute significantly to diversity in the third hypervariable region. Thus, it appears that sheep, like all other mammals studied to date, employ somatic rearrangement of multiple germline genes to create beta-chain heterogeneity. These findings have allowed us to estimate the diversity of the sheep T-cell receptor beta-chain variable region repertoire, and they provide information that will permit the evaluation of the role that specific T-cell populations play in naturally occurring and experimental diseases of sheep.