Identification of Rfp-Y (Mhc-like) haplotypes in chickens of Cornell lines N and P

Two strains of chickens selected for differential Marek's disease (MD) resistance or susceptibility were studied for the presence of the recently described Rfp-Y major histocompatibility complex (Mhc-like) haplotypes, Mn resistant chickens from line N were fixed for the classical Mhc B-21 haplotype, whereas MD susceptible line P chickens were fixed for the B-19 haplotype, the Rfp-Y haplotypes were identified by restriction fragment polymorphism (RFP) analysis using enzymes and Mhc probes for B-G, B-L beta II, and B-FIV, In addition an Rfp-L beta III clone was developed that differentiated Rfp-Lp from B-LP genes, Three Rfp-Y haplotypes, defined for both class I and class II Mhc-like loci, were identified in line N (Rfp-Y-5, Rfp-Y-7, and Rfp-Y-8) and in line P (Rfp-Y-5, Rfp-Y-8, and Rfp-Y-9), respectively. The Rfp-Y-7, Rfp-Y-8, and Rfp-Y-9 haplotypes have not been described previously. The Rfp-Y-5 haplotype was most frequent (0.70) in line N, but existed in low frequency (approximately 0.04) in line P; the Rfp-Y-9 haplotype was most frequent in line P (0.63), but was absent in line N, The Rfp-Y haplotypes segregated in a Mendelian fashion in each line based on analysis of progeny from Rfp-Y heterozygous matings, The frequency of recombination between the Rfp-Y F and L loci was estimated to be less than 0.25%.