A ROLE FOR THE CYTOPLASMIC TAIL OF THE BETA-CHAIN OF CD8 IN THYMIC SELECTION

The CD8 coreceptor plays a critical role in the recognition of foreign antigens by mature T cells and in the development of class I-restrict ed T cells. CD8 can be expressed on the surface of T cells as either a heterodimer composed of an alpha and beta chain, or as a homodimer co mposed of two alpha chains. In this report, we show that a CD8 beta tr ansgene that lacks a cytoplasmic domain can suppress expression of wil d-type endogenous CD8 beta and act as a dominant negative mutation. We show that this dominant negative CD8 beta transgene interferes with t he development of mature CD8 T cells to different extents depending on the individual class I-restricted TCR. These data suggest CD8 beta pl ays a role in thymic development, and that different class I-restricte d TCRs differ in their dependence on the cytoplasmic tail of CD8 beta.