'Hybrid resistance' against parental tumors: One or several genetic patterns?

A spectrum of lymphomas, sarcomas, and carcinomas were tested for F(1) hybrid resistance after s.c. inoculation of small numbers of cells into syngeneic and F(1) hybrid mice. Significant F(1) resistance was demonstrated against all tumors tested except one. Backcross and/or congenic inoculation tests showed significantH-2 linkage of hybrid resistance against all lymphomas and leukemias tested. There was no linkage betweenH-2 and hybrid resistance within the more limited group of carcinomas and sarcomas. DifferentH-2-linked resistance genes were shown to act against different lymphomas, including some that were induced by the same agent. Some lymphomas induced by different agents in the same strain were also found to differ in their sensitivity to the sameH-2-linked resistance factor. These data suggest the existence of a polymorphic system, probably pseudoallelic, rather than simply allelic in nature.