Search

Tsud (ref. 1) is an alloantigen on mouse suppressor T cells, coded for by a gene downstream from the immunoglobulin locus on chromosome 122. We now report a second T-cell alloantigen, Tindd, which is closely linked to Tsud. Both antigens may be products of a family of genes coding for conserved, non-antigen binding site regions of T-cell receptors. Tindd is defined by a monoclonal BALB/c (Igh-1a) anti-C.AL-20 (Igh-1d) antibody and is expressed preferentially on Lyt 1+2−3− peripheral lymphoid cells, whereas Tsud is expressed on Lyt 1−2+3+ suppressor cells. The interpretation that these determinants represent antigen binding molecules is in part based on the antibody-mediated induction of cell function. In vivo treatment of C.AL-20 animals with anti-Tsud antiserum at day 4 suppresses the primary immune response to sheep red blood cells (SRBCs)3–5. Pretreatment with limiting dilutions of anti-Tindd antibody induces cyclic waves of either suppression or enhancement of the plaque-forming cell response. The genes coding for these determinants have now been mapped in inbred congeneic mice having recombination events in or near the immunoglobulin locus. Monoclonal anti-Tindd antibodies precipitate a group of polypeptides of molecular weights (MWs) 62,000, 45,000 and 17,000 from 35S-methionine-labelled spleen cells activated with concanavalin A (Con A) whereas the polypeptides associated with the Tsud specificity have MWs 69,000, 45,000 and 25,000. The differences in molecular weights and contrast in the Lyt phenotype of cells expressing these antigens suggest they are separate molecules and may imply discrete isotypes of T-cell receptor.