T‐Cell Receptor Alpha Haplotype influences Vα Epitope Expression on both Cortisone‐Resistant Thymocytes and Lymph Node T Cells

We have previously described a mouse strain congenic for the T-cell receptor alpha chain locus (Tcra). The strain, B10.D2.C-Tcraa/Bo, carries the Tcraa haplotype of BALB/c instead of the Tcrab haplotype normally found in B10.D2. By comparing B10.D2.C-Tcraa and B10.D2 mice, we now show that the Tcra haplotype influences the frequencies of V alpha 8 epitope expression on T cells detected by the novel B21.14 monoclonal antibody (MoAb). This finding agrees well with our previous observation that Tcra haplotype influences the frequencies of expression of two other V alpha 8 epitopes, detected by the KT50 and KT65 MoAbs. The specificities of the three V alpha 8-specific MoAbs were compared by scatter diagram analysis of staining frequencies obtained in individual mice. The B21.14 and KT50 MoAbs appear to have very similar specificities; these two MoAbs stain slightly more alpha beta T cells than the KT65 MoAb. Investigations with another novel MoAb, the V alpha 2-specific B20.1, revealed that the Tcra haplotype also influences the frequency of V alpha 2 epitope expression. The effect of the Tcra haplotype on V alpha 2 epitope expression was evident not only among lymph node T cells but also among mature, cortisone-resistant thymocytes. Thus, the influence of the Tcra haplotype is imprinted already in the thymus. The most likely explanations for Tcra haplotype dependency of V alpha epitope expression are differing numbers of V alpha-gene segment subfamily members and/or allelic polymorphism. The significance of Tcra haplotype-dependent V alpha epitope expression is discussed.