Genetic nature of regression of Rous sarcoma virus-induced tumors in crosses of regional poultry research laboratory lines 6 and 7

Regional Poultry Research Laboratory (RPRL) inbred lines 6(1), 6(3), and 7(2) and F1, F2, and reciprocal backcross progenies of these lines were used to investigate host-gene effects upon the regression of Rous sarcoma virus (RSV)-induced tumors. Lines 6(1) and 6(3) were susceptible to subgroup A and C lymphoid leukosis (LL) viruses and line 7(2) was resistant to subgroup A but was segregating for susceptibility to subgroup C LL virus. Viruses of RSV subgroups A and C were used. Lines 6(1), 6(3), and 7(2) were homozygous for shared blood group alleles B2, C5, L1 and r. The incidence of tumor regression was higher in line 6(3) than in 7(2), and in reciprocal F1 crosses of these lines was of the same order of magnitude as in line 6(3). Progeny from F1 generation parents mated to line 6(3) had a higher frequency of regression than offspring from F1 generation parents mated to line 7(2). The frequency of regression in F2 generation offspring was intermediate between the two backcrosses. The data suggest that either a locus (or loci) other than L and B has a role in Rous tumor regression in this species or the immune response region of the B blood group-major histocompatibility complex differs in the two lines even though the serological and/or graft vs. host regions have not been shown to differ.