Regulation of allogeneic responses by expression of CD8 alpha chain on stimulator cells.

By antisense-mediated inhibition of CD8 expression in T cell clones and expression of CD8 in non-T cell lines, we have produced several sets of CD8+/CD8- paired cell lines. These cellular reagents have allowed us to assess the effect of CD8 surface expression on the immunogenic potential of stimulator cells. We found that the presence of CD8 on stimulator cells markedly decreased their capacity to stimulate proliferative responses or to induce the generation of cytotoxic activity. The CD8 alpha chain, in the absence of the beta chain, was sufficient to mediate this inhibitory effect. Our findings support the notion that CD8 functions as an immunoregulatory ligand and that auxiliary cell surface molecules on stimulator cells can have profound effects on the immunogenic capabilities of these cells.