Impact of major histocompatibility complex class II polymorphisms on Iberian red deer parasitism and life history traits.

ABSTRACT

Host genetic diversity plays an important role in buffering populations against pathogens. We characterized the allelic diversity at the second exon of the b (DRB-2) chain of the major histocompatibility complex class II (MHC-II) locus in a population of Iberian red deer (Cervus elaphus hispanicus) and its impact on parasitism by macroparasites, on a microparasite causing tuberculosis, and on relevant life history traits (spleen size and body condition). No DRB-2 haplotype conferred general resistance or susceptibility against all parasites. However, specific significant correlations were found between some DRB-2 haplotypes and specific parasites. We also detected associations between DRB-2 haplotypes and body condition and spleen size after controlling for body size, sex and age. Our results evidenced a functional significance of MHC-II genes in the defence of Iberian red deer against parasites. These results also support a role of MHC-II as a fitness-enhancing genetic element which can be mediated by parasite effects on life traits with a genetic basis. We conclude that MHC immunogenetic studies may assess management decisions in Iberian red deer because (i) loss of genetic diversity may lead to increased disease occurrence, and (ii) MHC genes are ecologically relevant since they underlie host infection rates and life history traits.