Mouse strain differences in subset distribution and T cell antigen receptor expression among CD4 − CD8 − thymocytes

Summary ‘Double negative’ (CD4 − CD8 − ) thymocytes from adult mice of different inbred strains were examined for surface expression of CD3 and of various forms of the T cell antigen receptor (TcR), as well as for the levels of subpopulations defined by the surface markers HSA (‘heat stable antigen’, recognized by M1/69, J11d and B2A2), CD5 (Ly 1) and Thy 1. Marked variations were found in the level of the double negative subsets which were surface TcR + , or which were HSA − CD5 + ; these generally varied together since most CD4 − CD8 − HSA − CD5 + thymocytes were TCR + . The level of the CD3‐TCR complex on the surface of those double negative thymocytes which were TcR + was as high as on mature T cells in some strains (CBA/Ca), but was much lower in other strains (C57BL/6J). In most mouse strains the CD4 − CD8 − HSA − CD5 + thymocytes expresed predominantly the αβ form of the TcR, with an exceptionally high (70%) usage of Vβ8 gene products. In strains which lacked Vβ8 expressing T cells due to a deletion of the Vβ8 gene region, reduced levels of αβTcR + cells were found within the CD4 − CD8 − thymocytes; the HSA − CD5 + subset was then only present at low levels (as in SJL/J and C57BR mice)or was present at a high level but expressed predominantly γδTcR (as in SWR mice). The results suggest that the accumulation of CD4 − CD8 − TcR + HSA − CD5 + thymocytes is a selective event, and that their developmental pathway is off the mainstream of T cell maturation in the thymus.