MOLECULAR CHARACTERIZATION OF 3 MHC CLASS-II B-HAPLOTYPES IN THE RING-NECKED PHEASANT

We investigated the class II B genes in a free-ranging population of t he ring-necked pheasant Phasianus colchicus by a combination of restri ction fragment length polymorphism (RFLP), polymerase chain reaction ( PCR), and DNA sequencing. Special attention was paid to the variation in the second exon, which encodes the peptide-binding beta(i)-domain. The population was introduced, but it still exhibited major histocompa tibility complex polymorphism with at least three segregating class II B haplotypes and consequently six genotypes. We found two class LI B genes associated with each haplotype. The class II B genes of birds ha d until then only been molecularly characterized in the domestic chick en. The pheasant genes were highly variable, although one of the ampli fied sequences was found in two different haplotypes. Taken together, the most polymorphic positions (residues 37 and 38) were not identical in any of the predicted protein sequences, but all except one of the motifs had already been found in the domestic chicken. Structurally im portant features in mammalian class II B genes were generally conserve d also in the pheasant sequences, but the loss of a potential salt bri dge constituent (Arg(72)) in several sequences may suggest a slightly different structure of the adjacent parts of the peptide-binding groov e. The pheasant genes are most closely related to the so called B-LBII family in the chicken, indicating that this represents a major line o f development among avian class II B genes.