Natural suppressor cell inhibiting T killer responses against retroviruses: a model for self tolerance.

We previously reported the characterization of a spontaneous suppressor T cell population (NSC) present in naive mice and able to suppress the cytotoxic response (CTL) against tumor cells induced only by endogenous Gross virus (GLV). In this study we demonstrate the existence of such NSC inhibiting the CTL activity against tumor cells induced by the normally exogenous Moloney virus (M-MLV) in mice of the Mov-13 (V+) strain in which the M-MLV has been artificially endogenized and which express the virus during the embryonal life. These NSC are not found in other Mov strains in which the endogenized M-MLV is not expressed during fetal life. The implication of these data in the mechanism of self tolerance is discussed.