ENDOGENOUS SUPERANTIGEN EXPRESSION IS CONTROLLED BY MOUSE MAMMARY-TUMOR PROVIRAL LOCI

Superantigens are defined by their ability to stimulate T cells based predominantly on their V-beta expression and ability to delete T cells in the thymus when expressed endogenously. We show here that the expression of one endogenous superantigen, Etc-1, is controlled by the expression of the open reading frame region of the 3' long terminal repeat of the mouse mammary tumor proviral gene, Mtv-9. We show that Mtv-8 controls a superantigen with similar specificity, and that both Mtv-8 and Mtv-9 stimulate some V-beta-17+ T cells. A third provirus, Mtv-6, controls a superantigen with specificity for V-beta-3. Data presented raise the possibility that endogenous superantigens may compete for class II molecules in a single B cell.