MHC-DRB evolution provides insight into parasite resistance in white-tailed deer

摘要

The major histocompatibility complex (MHC) is a gene complex closely linked to the vertebrate immune system due to its importance in antigen recognition and immune response to pathogens. As a result, the MHC has been considered a basis for genetic quality because of the devastating impact that parasites and disease can have on fitness. To improve our understanding of the MHC and parasite resistance in free-ranging species, we gathered data on genetics and parasite loads of white-tailed deer (Odocoileus virginianus) to determine whether the DRB region of the MHC contains alleles that are associated with abundance, intensity, and prevalence of parasites. Mean abundance and intensity of abomasal nematodes were strongly associated with phylogenetic groupings of Odvi-DRB alleles. Infection of ectoparasitic ticks was strongly associated with Odvi-DRB alleles but had a positive association with alleles from a different evolutionary lineage than abomasal nematodes. Our data suggest that allelic composition of the Mhc-DRB of white-tailed deer in southeastern Oklahoma might represent a genetic trade-off. Deer with alleles from the same Mhc-DRB evolutionary clade had strong resistance to one class of parasite, either abomasal nematodes or ectoparasitic ticks, whereas deer with alleles from both lineages tended to have moderate resistance to both pathogens, although weaker.