Selection for antibody response against sheep red blood cells alters multiple chicken alloantigen allele frequencies.

Chicken erythrocyte alloantigens were first identified using specific antisera. Recent work has developed SNP assays to identify alloantigen genes and their chromosomal location. This study's objective was to identify alloantigen systems A, B, D, E, and I variation in two pairs of lines, with different parental breed origin after multiple generations of divergent selection for antibody response against sheep red blood cells (SRBC) using allele-specific SNP assays and to compare allele frequencies across selected lines. Cornell Randombred White Leghorn founders at Virginia Tech were selected for high (VA-HAS) or low antibody (VA-LAS) response to intravenous immunization of SRBC at each generation. One hundred randomly selected generation 48 progeny were examined from each line. A second set of lines were selected from a ISA Warren medium heavy brown layer population at Wageningen University (WUR) for high (WUR-HA) or low antibody (WUR-LA) titers following subcutaneous immunization with SRBC at each generation. A random-bred control line (WUR-CON) was maintained as well. Selection generation 32, including 136 WUR-HA, 124 WUR-LA and 64 WUR-CON chickens, were tested for alloantigen genotypes. Haplotype frequencies were determined and compared between pairs of lines, using the chisq.test function in R. Lines VA-HAS and VA-LAS had 2 to 5 alleles for each alloantigen with frequencies differing significantly between the lines for all five alloantigen systems. Alloantigen B (MHC) frequencies had striking divergence with each line being nearly homozygous for alternate alleles, as reported previously. Lines WUR-HA and WUR-LA had 3 to 6 alleles for each alloantigen. Alloantigen frequencies for systems A, B, D, and E but not I differed significantly between WUR-HA and WUR-LA. The WUR-HA and WUR-LA allele frequencies differed significantly from WUR-CON, except for the D system in WUR-LA chickens. Alloantigen frequency shifts in two different breeds under similar selection protocols for the specific antibody response against SRBC suggests that alloantigens other than the B system (MHC) are associated with specific antibody response.