A Possible T Cell Receptor Allotype

We have described a mouse T cell alloantigen, Tsud, 1 which may be an allotypic or idiotypic determinant on a T cell receptor (1-3). Tsu d is associated with the T cell receptor for idiotype, apparent ly on suppressor T cells or their precursors (2). The determinant is defined by antisera made in B A L B / c mice against T cell blasts from allotype congenic C.AL-20 mice and can be detected by immunofluorescent staining on suhpopulat ions o f splenic Lyt-2 + T cells, concanaval in A blasts, and mature thymocytes. It cannot be detected on Lyt-1 + T cells, prethymocytes, or B cells (1). Antiserum against Tsu d induces the product ion of T suppressor cells for the ant ibody responses to various T dependent antigens (3). The expression of Tsu d is controlled by a gene closely linked to the immunoglobul in heavy chain gene cluster, Igh. Only strains possessing the Igh a or lgh e heavy chain haplotypes, such as A K R , A L / N , A, and NZB, express Tsu d, and the linkage suggested by this association is confirmed by the appearance o f T s u d in the allotype congenic strain C.AL-20 (I), as well as by the findings reported here. T he allotype linkage o f T s u d and its association with the T cell receptor suggested that Tsu d might be an allotypic or idiotypic determinant of an immunoglobul in heavy chain that forms part of the T cell receptor. Several other studies have reported heavy chain determinants associated with T cell receptors. There are reports of ant ibody idiotype and specific heavy chain idiotype markers associated with T cell receptors (4-6), and more recently a heavy chain variableregion (Vh) 2 framework determinant has been found on T cells (7). These and other studies have failed to demonstrate immunoglobul in light chain markers or heavy chain constant-region allotypes on T cells, suggesting that a T cell receptor may consist of a heavy chain variable region expressed with a T cell-specific constant region either alone or in combina t ion with a protein other than immunoglobul in light chain. The Tsu d determinant could then be a V h idiotype or framework marker.