RESPONSE OF 6 MAJOR HISTOCOMPATIBILITY (B) COMPLEX RECOMBINANT HAPLOTYPES TO ROUS SARCOMAS

Six B complex recombinants, B(R1) (F24-G23), B(R2) (F2-G23), B(R3) (F2 -G23), B(R4) (F2-G23), B(R5) (F21-G19), and B(R6) (F21-G23), from the fourth backcross generation to highly inbred line UCD 003 (B17B17) wer e studied for their response to Rous sarcomas. Eight hatches were prod uced from heterozygous (B(Rn)B17) parents. Chicks were wingweb inocula ted 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. B(R2), B(R3), and B(R4) are se rologically similar F2-G23 recombinants. Haplotype B2, the origin of B (F2), is a known tumor regressor, yet B(R2)B(R2) chickens had a signif icantly lower TPI than B(R3)B(R3) and B(R4)B(R4) chickens. The TPI of B(R2)B(R2) (F2-G23) chickens was also significantly lower than the TPI of chickens homozygous for B(R1) (F24-G23) and B(R5) (F21-G19). The B (R6)B(R6) (F21-G23) chickens had significantly lower TPI than all homo zygotes except B(R2)B(R2) (F2-G23). Among heterozygous genotypes, B(R2 )B17, B(R5)B17, and B(R6)B17 differed significantly from B(R1)B17, B(R 3)B17, and B(R4)B17. These results suggest that serologically similar recombinants that contain (F2-G23) possess different genes affecting t umor regression. In addition, degrees of tumor regression in B(R5) (F2 1-G19) and B(R6) (F21-G23), both of which contain B(F21), may be due t o genetic differences within the B-F/B-L or B-G regions.