PCR-RFLP analysis of β1 domain of MHC class II β region in Aseel and immunodivergent chicken lines

BL-βII region of chicken MHC was analyzed in Aseel (Peela) a native breed of chicken with much less history of selection for economic traits and high yielding white plumaged Synthetic Broiler Dam Line (SDL), divergently selected for response to sheep RBCs (SRBC). Response to SRBC (0.5% suspension, i/v) was estimated by HA test after 5 days post immunization and high (HSRBC) and low (LSRBC) responding lines to SRBC were generated. DNA was isolated from extreme responders of divergent lines after second generation (F2) of selection as well as randomly chosen individuals of Aseel. BL-βII region was amplified as 277 bp using specific primers. PCR products were purified and digested with Taq I enzyme. Subsequent to polyacrylamide gel electrophoresis and silver staining a total of two genotypes i.e. AA and AC were observed in SDL birds with genotypes frequencies of AA genotype as 0.9 and 0.3 in HSRBC and LSRBC, lines respectively. Corresponding values for AC genotype were 0.1 and 0.7. However, individuals from Aseel breed exhibited monomorphic pattern with genotype AA at frequency 1.0. The polymorphism between immuno-divergent broiler lines suggested that selection for SRBC response has influenced the genotype frequency of BL-βII region between the lines. Aseel (peela) breed is known for fighting abilities and has much higher genetic resistance to diseases as compared to high yielding stocks. Monomorphic pattern in Aseel (peela) could be due to fixation of naturally selected genotype -AA. Higher frequency of genotype AA in HSRBC line of SDL and Aseel (peela) indicated that genotype AA might be associated with selective advantage with humoral immune response trait. Taq I PCR-RFLP analysis of BL-βII region may be used as a tool to evaluate MHC polymorphism in chickens.