Segregation of chicken MHC-Y haplotypes in high and low antibody selected lines provides evidence that MHC-Y contributes to the genetics of immune responses

Abstract

Abstract MHC-Y is a second genomic region in chickens containing genes encoding highly polymorphic MHC class I molecules. MHC-Y class I molecules have a distinctive surface distribution of polymorphic residues. The function of MHC-Y class I molecules is unknown. To begin to determine whether genetic differences at MHC-Y influence immune responses, we have defined the MHC-Y haplotypes segregating in the Virginia Tech high antibody (HAS) and low antibody (LAS) lines. HAS and LAS have been selected for 45 generations for high and low antibody responses to sheep red blood cells, respectively. The HAS and LAS lines are known from previous studies to differ at a number of loci that influence immune responses, including the classical MHC-B region. We MHC-Y typed the HAS and LAS lines at the 44th and 45th generation using a microsatellite sequence found immediately upstream of the MHC-Y class I gene start sites. Typing revealed the presence of five MHC-Y haplotypes overall. Two haplotypes were found only in the HAS line. The frequency of one haplotype was 60%. In LAS, three other haplotypes were common. The separation of different MHC-Y haplotypes in the HAS and LAS lines suggests that MHC-Y locus is another polymorphic genomic region changing in response to selection for high and low antibody phenotypes. This finding is among the first linking MHC-Y genetics to immune responses in chickens. Supported in part by USDA NIFA Grant 2016-10247.