B-complex recombinants and sarcoma regression: role of B-L/B-F region genes.

The anti-sarcoma response of three B complex recombinant haplotypes BR1(F24-G23), BR2(F2-G23), and BR3(F2-G23) was investigated. In a preliminary experiment, one male heterozygous for the BR1 recombinant haplotype and another heterozygous for the BR2 recombinant haplotype were each mated to females, some of which carried the respective recombinant. The anti-sarcoma response of progeny carrying the BR1 recombinant differed significantly from that of progeny carrying the BR2 recombinant. Subsequently, each of the three recombinant haplotypes was placed on each of four B haplotype complex backgrounds, and compared to B-G and B-L/B-F region controls on the same background haplotype. For each recombinant, significant differences in tumor growth were found between the recombinant and B-L/B-F control chickens on either one, two, or three of the four genetic backgrounds tested. For each recombinant, no differences were found between chickens carrying the recombinant and B-G region controls, which is further evidence that the gene(s) controlling Rous sarcoma growth lies in or near the B-L/B-F chromosomal region. Moreover, although the BR2 and BR3 recombinants appear to be identical serologically, they differed significantly in tumor growth suggesting that the two haplotypes are genetically different.