Related Experiment Video

Updated: Oct 14, 2025

Immunopeptidomics: Isolation of Mouse and Human MHC Class I- and II-Associated Peptides for Mass Spectrometry Analysis
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Immunopeptidomics: Isolation of Mouse and Human MHC Class I- and II-Associated Peptides for Mass Spectrometry Analysis

Published on: October 15, 2021

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

Wei Huang1, Kara L Dicks1, Keith T Ballingall2

  • 1Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.

Molecular Ecology
|November 8, 2021
PubMed

Insights

Major histocompatibility complex (MHC) class II variation in sheep is linked to immune responses, specifically immunoglobulin levels, but not to weight or parasite egg counts. This suggests MHC influences pathogen defense traits more directly than general fitness indicators.

Area of Science:

  • Immunogenetics
  • Evolutionary biology
  • Wildlife immunology

Background:

  • Pathogen-mediated selection (PMS) is a key hypothesis for maintaining high allelic diversity in Major Histocompatibility Complex (MHC) genes.
  • Examining associations between MHC variation and fitness indicators, such as immune responses and phenotypic traits, is crucial for demonstrating contemporary selection.
  • Individual fitness is challenging to measure directly, leading to the use of proxy traits like adaptive immunity measures.

Purpose of the Study:

  • To investigate the association between MHC class II variation and specific phenotypic traits in free-living sheep.
  • To determine if MHC variation correlates with traits directly related to pathogen defense (immunoglobulin levels, parasite egg counts) versus general fitness indicators (body weight).

Main Methods:

  • Phenotypic data, including body weight, strongyle fecal egg count, and plasma immunoglobulin (IgA, IgE, IgG) titers against Teladorsagia circumcincta, were collected from free-living sheep.
  • MHC class II variation was analyzed in relation to these five phenotypic traits.
  • Statistical associations between MHC class II genotypes and measured traits were assessed.

Main Results:

  • No significant associations were found between MHC class II variation and body weight or strongyle fecal egg count.
  • Significant associations were identified between MHC class II variation and plasma immunoglobulin levels (IgA, IgE, IgG).
  • These associations with immunoglobulin levels were further influenced by the isotype, age, and sex of the sheep.

Conclusions:

  • MHC class II variation is associated with immune response traits, particularly antibody production, in wild sheep populations.
  • The findings support the idea that MHC-phenotype associations are more readily detected for traits closely linked to pathogen defense than for integrative traits like body weight.
  • This study highlights the role of MHC variation in shaping adaptive immune responses to parasites in natural settings.
Keywords:
Soay sheepimmune responsemajor histocompatibility complexparasitephenotypic traitselection

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