T-CELL RECEPTOR ALPHA-HAPLOTYPE INFLUENCES V-ALPHA EPITOPE EXPRESSIONON BOTH CORTISONE-RESISTANT THYMOCYTES AND LYMPH-NODE T-CELLS

We have previously described a mouse strain congenic for the T-cell re ceptor alpha chain locus (Tcra). The strain, B10.D2.C-Tcra(a)/Bo, carr ies the Tcra(a) haplotype of BALB/c instead of the Tcra(b) haplotype n ormally found in B10.D2. By comparing B10.D2.C-Tcra(a) and B10.D2 mice , we now show that the Tcra haplotype influences the frequencies of Va lpha8 epitope expression on T cells detected by the novel B21.14 monoc lonal antibody (MoAb). This finding agrees well with our previous obse rvation that Tcra haplotype influences the frequencies of expression o f two other Valpha8 epitopes, detected by the KT50 and KT65 MoAbs. The specificities of the three Valpha8-specific MoAbs were compared by sc atter diagram analysis of staining frequencies obtained in individual mice. The B21.14 and KT50 MoAbs appear to have very similar specificit ies; these two MoAbs stain slightly more alphabeta T cells than the KT 65 MoAb. Investigations with another novel MoAb, the Valpha2-specific B20.1, revealed that the Tcra haplotype also influences the frequency of Valpha2 epitope expression. The effect of the Tcra haplotype on Val pha2 epitope expression was evident not only among lymph node T cells but also among mature, cortisone-resistant thymocytes. Thus, the influ ence of the Tcra haplotype is imprinted already in the thymus. The mos t likely explanations for Tcra haplotype dependency of Valpha epitope expression are differing numbers of Valpha-gene segment subfamily memb ers and/or allelic polymorphism. The significance of Tcra haplotype-de pendent Valpha epitope expression is discussed.