Genetic role of rat macrophage cytotoxicity against tumor.

Macrophages from the Lewis (Le) rat strain are significantly more cytotoxic to a Moloney sarcoma tumor both in vivo and in vitro, than are macrophages from the Brown Norway (BN) strain. Activity of macrophages from (Le x BN)F1 rats that are histocompatible with the Moloney sarcoma tumor is directed toward tumor and/or virus-associated antigens and is expressed as a dominant genetic trait. Experiments with backcross rats suggest that the genetic factors are unrelated to the major histocompatibility locus (AgB) of the rats. BN microphages, although not active against tumor and/or viral antigens, can become cytotoxic to cells displaying Le alloantigens.