Enhanced syngeneic tumor destruction by in vivo inhibition of suppressor T cells using anti-I-J alloantiserum.

The cellular response to a methylcholanthrene-induced sarcoma S1509a has been investigated. Histologic analysis of the in vivo response to S1509a included a study of tumor development in nonimmune, tumor immune, or hyerimmune syngeneic mice, as well as in nonimmune animals treated with antiserum produced to interact solely with determinants encoded by the I-J subregion of the H-2 major histocompatibility complex. Tumors from immune or hyperimmune mice showed marked infiltration by mononuclear and, to a lesser extent, polymorphonuclear cells, with marked tumor cell necrosis. Anti-I-J treated mice displayed similar but quantitatively reduced leukocytic infiltrates and less evidence of tumor cell degeneration. Untreated nonimmune mice, on the other hand, revealed only mild leukocytic infiltration with little or no necrosis of the tumor. Thus, the administration of anti-I-J antiserum, which has been shown to diminish suppressor cell activity, is associated with increased leukocytic infiltration and enhanced syngeneic tumor destruction in vivo in the nonimmune host.