Major histocompatibility complex variation and age-specific endoparasite load in subadult European rabbits

Abstract

Genes of the major histocompatibility complex (MHC) play a fundamental role in the vertebrate immune response and are amongst the most polymorphic genes in vertebrate genomes. It is generally agreed that the highly polymorphic nature of the MHC is maintained through host-parasite co-evolution. Two nonexclusive mechanisms of selection are supposed to act on MHC genes: superiority of MHC heterozygous individuals (overdominance) and an advantage for rare MHC alleles. However, the precise mechanisms and their relative importance are still unknown. Here, we examined MHC dependent parasite load in European rabbits (Oryctolagus cuniculus) from a distinct population with low MHC diversity (three alleles, six genotypes). Using a multivariate approach, we tested for associations of individual MHC class II DRB constitution and the rabbits' intestinal burden with nematodes and coccidia. Rabbits having a particular allele showed lower infestations with hepatic coccidia (E. stiedai). However, a comparison of all six genotypes in the population revealed that carriers of this allele only benefit when they are heterozygous, and furthermore, MHC heterozygosity in general did not affect individual parasite load. In conclusion, this study suggests an immunogenetic basis of European rabbit resistance to hepatic coccidiosis, which can strongly limit survival to maturity in this species. Our study gives a complex picture of MHC-parasite correlations, unveiling the limits of the classical hypotheses of how MHC polymorphism is maintained in natural systems.

Major Histocompatibility Complex, demographic, and environmental predictors of antibody presence in a free-ranging mammal

“…These results, combined with the fact that we detected significant associations between specific MHC alleles and seroprevalence, suggest that MHC II DRB variation in raccoons is under pathogen-driven selection. Disentangling the specific mechanisms by which selection acts is difficult since they are not exclusive (Oppelt et al, 2010;Spurgin and Richardson, 2010). Since we could not assign alleles to specific loci, we could not confidently test for heterozygote advantage.…”

Beyond splitting hares and rabbiting on about major histocompatibility complex complexity

“…The results from the studies of Smith et al (2010) and Oppelt et al (2010) reflect the reality that there is a consistent lack of consistency for evidence to support a particular mechanism driving MHC diversity. A lack of consensus across populations and taxa suggests that MHC diversity may be defined by an amalgam of effects, incorporating reproductive success, mating systems, antagonistic coevolution with parasites, fluctuating selection pressures, heterozygote advantage or copy number optimality, population demography and extrinsic environmental factors, all of which are likely to be context dependent.…”

“…1). Also in this issue, Oppelt et al (2010) demonstrate a role for MHC variation in determining levels of hepatic coccidian infection in the European rabbit Oryctolagus cuniculus (Fig. 2).…”

“…The paper by Oppelt et al (2010) is exemplary of this approach. In a semi-wild study system with only three MHC alleles and six MHC genotypes, they show that European rabbits with a certain MHC-DRB allele in the heterozygous state, but not homozygote state for that allele, or MHC-DRB heterozygotes per se, have reduced infections of hepatic coccidia, high infestations of which can be lethal to rabbits.…”

MHC-DRB1/DQB1 Gen Polimorfizmi ve Çin Merinos Koyununda Kistik Echinococcosise Dirençle İlişkisi

“…In 2001, it was proposed that MHC genes may be candidate genetic markers for disease resistance [1] . MHC genes play a central role in vertebrate immunity because they code for proteins that present peptides to T cells [2] . The immune response is triggered when MHC non-self-peptide complexes are recognized by T cells [3] .…”