Linkage disequilibrium ofMHC genes in the chicken

Two loci of the chicken MHC (theB complex) are expressed in erythrocytes,B-F andB-G. The former is homologous to the murineK andD loci and is also expressed in all white blood cells, while the latter is apparently restricted to RBC and is of unknown relationship toH-2 andHLA loci. A recombinant between two congenic, MHC-different strains, CB and CC, has permitted the production of antisera specific for theB-F andB-G alleles of these two strains, and these and other antisera have been used for typing of outbred populations of various chicken breeds.The cross-reactions found with haplotypes other than the donors' are extensive, sometimes even extreme, but it is possible to narrow the specificity of the typing sera by appropriate absorptions. With absorbed sera we have found a linkage disequilibrium which is almost certainly even stronger than that reported in studies of mammalianMHC loci. We have also made observations which suggest that the gametic association of a given set ofB-F andB-G alleles is probably not merely a matter of random crossing-over events.