Metastasis of Rous sarcoma tumors in chickens is influenced by the major histocompatibility (B) complex and sex

Six-week-old second generation progeny from the cross of inbred Lines 6(1) and 15(1), segregating into three major histocompatibility (B) complex groups (B2/B2, B2/B5, and B5/B5), were inoculated subcutaneously in the wingweb with one of three pseudotypes of Rous sarcoma virus. Chickens that died during a 10-week period after inoculation were necropsied and scrutinized for gross metastasis and histological sections of at least one lesion per affected organ examined for Rous sarcoma-transformed cells. By definition, a metastatic tumor was one located in an organ or tissue other than the primary inoculation site and having the histological appearance of a Rous sarcoma. Sarcomas developed in 1144 chickens, 390 of which died with tumor. For B2/B2, compared to B5/B5 hosts, mortality was 8 vs. 93%, median days to death were 45 vs. 31, and metastatic frequency was significantly lower, 32 vs. 58%. Disseminated lesions were significantly less frequent in females than males and grew preferentially in the heart and pericardial sac. Because the frequency of metastasis was significantly lower in B2/B2 than in B5/B5 chickens, a gene(s) within, or closely linked to, the B complex sharply retards the spread of Rous sarcoma virus-induced tumors.