Analysis of sheep T-cell receptor beta-chain heterogeneity

We analyzed nucleotide and deduced amino acid sequence heterogeneity of she ep T-cell receptor beta-chain cDNAs isolated from an anchored-polymerase ch ain reaction library. Evaluation of 34 individual rearrangements has define d 18 new beta-chain variable region sequences which have been clustered int o 13 families. Presumptive allelic polymorphisms of four of these variable regions have been defined, as well as ten distinct beta-chain joining regio n sequences. The present analysis indicates that sheep T-cell receptor beta -chains are composed of characteristic leader, variable, joining, and const ant region sequences, and that imprecise joining and N-region addition cont ribute significantly to diversity in the third hypervariable region. Thus, it appears that sheep, like all other mammals studied to date, employ somat ic rearrangement of multiple germline genes to create beta-chain heterogene ity. These findings have allowed us to estimate the diversity of the sheep T-cell receptor beta-chain variable region repertoire, and they provide inf ormation that will permit the evaluation of the role that specific T-cell p opulations play in naturally occurring and experimental diseases of sheep.