Associations between MHC class II variation and phenotypic traits in a free‐living sheep population

Abstract

The immune system provides a variety of mechanisms to protect the host from infection by rapidly evolving and highly variable pathogens. The diversity of immune-related proteins and their associated genes are believed to have evolved in response to such pathogen diversity via the process of coevolution (Eizaguirre et al., 2012b;Pilosof et al., 2014). Among the proteins directly involved in the initiation of adaptive immunity, major histocompatibility complex (MHC) molecules, encoded by MHC class I and class II gene families, are the most variable and have been intensively researched in many species (Bernatchez & Landry, 2003;Edwards & Hedrick, 1998;Piertney & Oliver, 2006;Radwan et al., 2020). MHC genes encode heterodimeric MHC molecules which bind and present self-and pathogen-derived peptides to T cells to invoke and coordinate the adaptive immune response. Classical MHC class I genes

The genetics of immune and infection phenotypes in wild mice, Mus musculus domesticus

“…Interestingly, we found that the genotype of the MHC H2-Ab locus was associated with both IgG concentration and intestinal worm burden and there is the possibility that this is causal. Associations between MHC loci and antibody response in wild populations have been described in other mammals such as Soay sheep (Huang et al, 2022; but also see in other species reported in Gaigher et al, 2019). We also found associations between the MHC H2-Aa locus and various populations of DCs, CD4+ and CD8+ T cells, and MDSCs, as well as on ectoparasite burden.…”

“…Studies of polymorphisms in TLR and cytokine‐coding loci have also found associations with infection phenotypes. Most of these studies have studied the effects of polymorphism in immune‐related loci on infection phenotypes (especially of macroparasite burden), and so there remains major gaps in our understanding of effects on immune responses themselves (but see Charbonnel et al, 2010; Cutrera et al, 2011; Turner et al, 2011; Huang et al, 2022). Overall, polymorphism in rather few immune‐related loci has been studied in wild mammals, again in notable contrast to the very large number of loci studied in laboratory animals.…”

Twenty-year co-evolutionary arms race between meerkat MHC and Tuberculosis

“…Evidence of NFDS in natural study systems has been lacking because most studies so far reported shortterm snapshots of MHC-pathogen associations. The few studies that endeavored to track MHCpathogen associations over time showed either inconsistent results or were unable to document that alleles can lose or (re)gain resistance bene ts over time 17,34 . Three decades of tracking and monitoring meerkats since 1993 saw a rise in meerkat tuberculosis in the studied population 30 .…”

“…As stated earlier, bene ts of single alleles against speci c pathogens have been found repeatedly [44][45][46] . Aside from Soay sheep 34,40 , multi-year MHC studies that could tackle how important NFDS is in natural population, are rare. Frequency changes between generations, however, were shown in sticklebacks (Gasterosteus aculeatus) 11 , guppies (Poecilia reticulata) 13,14 , Scandinavian great reed warblers (Acrocephalus arundinaceus) 47 and Scottish populations of water voles (Arvicola terrestris) 18 , and form a prerequisite for NFDS arising from rare allele advantage.…”