Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/1996
Publication Date: N/A
Interpretive Summary: In chickens one group of genes that is variable within and between individuals is termed the B complex of genes. Thus, an individual may have inherited two identical B genes (1/1), or two different B genes (1/2), from their parents. The different B genes in chickens are known to influence the rejection of skin grafts, e.g., 1/1 chickens may accept grafts from compatible 1/1 chickens, but will rapidly reject grafts from incompatible 1/2 or 2/2 chickens. The B group of genes is, therefore, called the major histocompatibility complex. The B group of genes is also known to determine resistance to some common chicken diseases, including Marek's disease. Recently, a second group of genes very similar to the B complex of genes was described in chickens of line crosses. These genes are termed the Rfp-Y complex, and are inherited independently from B complex genes. This study determines the types of Rfp-Y genes in two random breeding chicken lines, i.e. lines N and P, which are respectively selected for resistance or susceptibility to Marek's disease. An improved method for identification of Rfp-Y genes is described. Three Rfp-Y genes were demonstrated in each line. Three of the four Rfp-Y genes identified have not been described previously. This data demonstrates that variability for Rfp-Y genes exists within lines of chickens. It is concluded that variability for Rfp-Y genes may be beneficial for chickens, and that Rfp-Y genes, like the closely related B genes, may also be important in disease resistance.
Technical Abstract: Two strains of chickens selected for Marek's disease (MD) resistance were studied for the presence of the recently described Rfp-Y major histocompatibility complex (Mhc) haplotypes. MD 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-LbetaII and B-FIV. In addition, a Rfp-LbetaIII clone was developed that differentiated Rfp-Lbeta from B-Lbeta genes. Three Rfp-Y haplotypes, defined for both class I and class II Mhc 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**8 haplotype was most frequent (.70) in line N, but existed in low frequency (approximately .04) in line P, while the Rfp-Y**9 haplotype was most frequent in line P (.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.