Response of six major histocompatibility (B) complex recombinant haplotypes to Rous sarcomas.

Six B complex recombinants, BR1 (F24-G23), BR2 (F2-G23), BR3 (F2-G23), BR4 (F2-G23), BR5 (F21-G19), and BR6 (F21-G23), from the fourth backcross generation to highly inbred line UCD 003 (B17B17) were studied for their response to Rous sarcomas. Eight hatches were produced from heterozygous (BRnB17) parents. Chicks were wingweb inoculated with 50 pock-forming units of Rous sarcoma virus (RSV) at 6 wk of age. A tumor profile index (TPI), based on degree of tumor regression, was evaluated by analysis of variance. BR2, BR3, and BR4 are serologically similar F2-G23 recombinants. Haplotype B2, the origin of BF2, is a known tumor regressor, yet BR2BR2 chickens had a significantly lower TPI than BR3BR3 and BR4BR4 chickens. The TPI of BR2BR2 (F2-G23) chickens was also significantly lower than the TPI of chickens homozygous for BR1 (F24-G23) and BR5 (F21-G19). The BR6BR6 (F21-G23) chickens had significantly lower TPI than all homozygotes except BR2BR2 (F2-G23). Among heterozygous genotypes, BR2B17, BR5B17, and BR6B17 differed significantly from BR1B17, BR3B17, and BR4B17. These results suggest that serologically similar recombinants that contain (F2-G23) possess different genes affecting tumor regression. In addition, degrees of tumor regression in BR5 (F21-G19) and BR6 (F21-G23), both of which contain BF21, may be due to genetic differences within the B-F/B-L or B-G regions.