MHC and non-MHC genetic influences on Rous sarcoma metastasis in chickens

The B5/B5 genotype, in Leghorns, was associated with a high degree of metastasis of Rous sarcoma virus-induced tumors, but in combination with a Leghorn-New Hampshire background markedly less metastasis occurred. Initially, four mating types were used: B5/B5 X B5/B5 chickens from the F5 generation of the cross of Leghorn lines 6(1) and 15(1), B24/B24 X B24/B24 chickens from line UNH 105 (New Hampshires), and reciprocal crosses of B5/B5 X B24/B24 chickens. Subsequently, F2 generation progeny of the cross of B5/B5 and B24/B24 breeders, as well as B24/B24 line UNH 105 and B5/B5 (6(1) X 15(1))F2 chickens, were used. Six-week-old chickens were inoculated in the wingweb with Rous sarcoma virus. Chickens dying during a 10-week period after inoculation were necropsied and suspect metastatic lesions examined histologically. Among 234 terminal chickens from the initial four mating types the incidence of metastasis associated with B5/B5 Leghorns (66%) was substantially higher than for B24/B24 New Hampshires (12%) and B5/B24 progeny of reciprocal Leghorn-New Hampshire crosses (19 and 24%). Subsequently, among 524 terminal hosts in the Leghorn-New Hampshire F2 population, B genotype significantly influenced tumor dissemination. However, among 52 concurrently challenged B5/B5 hosts from the (6(1) X 15(1))F2 population the incidence of metastasis (60%) was significantly higher than among 122 B5/B5 hosts from the Leghorn-New Hampshire F2 population (31%), indicating a non-major histocompatibility complex genetic effect on metastasis.