Rous sarcoma regression in seven highly inbred lines of White Leghorns

Response to Rous sarcoma virus (RSV)-induced tumors was studied in Regional Poultry Research Laboratory (RPRL) lines 61, 63, 72, 100, 151, and 15I5 and in Reaseheath line C, all highly inbred White Leghorn stocks. Virus inoculations were made in chickens at 6 weeks of age. Tumors were scored subjectively for size on a regular basis and in some instances a tumor profile index (TPI) was assigned which characterized tumor development over a 10 week period for each chicken (TPI 1 = complete regression in 28 days; TPI 5 = terminal tumor). The frequency of tumor regression, terminal tumors, and metastases and mean TPI was examined. The incidence of tumor regression ranged from 92% in line 61 to 0 % in lines 151 and 15I5. The frequency of terminal tumors varied from 100% in line 151 to 2% in line61, while metastasis in chickens with terminal tumors differed from 92% in line 15I5 to 0% in line 61. Mean TPI ranged from 2.0 in line 61 to 4.6 in line 15I5 and 4.7 in line C. The erythrocyte alloantigen genotype at the B blood group locus, (part of the B complex, MHC) and 11 additional blood group loci were known for each of the lines. The data indicate that genetic differences in tumor regression may be pronounced between inbred lines which share similar, if not identical, B locus erythrocyte alloantigens and that other unknown genes are also involved.