Determinants on T Cell Factors Coded

Thymus-derived(T) lymphocytes have been shown to display antigen specificity. The antigen-recognition units on T lymphocytes, in contrast to those on B lymphocytes, do not appear to be of the conventional immunoglobul in (Ig) type. Recent studies from various laboratories (1-5) have demonstrated that the antigen-specific T cell factors derived from helper or suppressor T cells possess the ant igen-binding moiety and the products of genes in the I region of the H-2 complex, whereas no Ig constant determinant has been defined. Antibodies against the variable (V) region of the Ig heavy chain (Igh) a or against idiotypes on the antibodies, however, have been shown to react with isolated T cell receptors for antigens as well as with antigenspecific helper and suppressor T cell factors (6-12). It is therefore suggested that the antigen-binding structure on T cell antigen-recognition units shares the V region markers with the conventional Ig on B cells. In this sense, the antigen-recognition units on T cells appear to possess a constant portion, as do Ig. However, the constant region determinants on T cell receptors or on antigen-specific T cell factors have so far not been defined. I f T cells utilize gene pools similar or identical to those coding for the V region of Igh (Igh-V), it is possible that the constant region determinants of the antigenrecognition units on T cells, distinct from those of B cell Igh (Igh-C), are also encoded by genes linked to the Igh locus. In this respect, the immunizat ion of mice with T cells from Igh allotype congenic mice would be able to provide antibodies specific for new allotypic determinants on the constant region of the antigen-recognition units of T cells. Based on these assumptions, Owen et al. (13-15) have, in fact, been successful in obtaining antisera reactive to the allotypic determinants on suppressor T cells of Igh-1 a mice (Tsu a) encoded by genes adjacent to the Igh constant-region genes, Igh-C, on the side toward the prealbumin gene, Pre-1. The Tsu a has been found to be expressed on Lyt-2 + suppressor T cells. Furthermore, the anti-Tsu a antisera stimulate suppressor T cells of mice that have an appropriate Igh allotype and block the binding