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Quantitative disease resistance: to better understand parasite-mediated selection on major histocompatibility complex.

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Author

Summary, in English

We outline a descriptive framework of how candidate alleles of the immune system associate with infectious diseases in natural populations of animals. Three kinds of alleles can be separated when both prevalence of infection and infection intensity are measured-qualitative disease resistance, quantitative disease resistance and susceptibility alleles. Our descriptive framework demonstrates why alleles for quantitative resistance and susceptibility cannot be separated based on prevalence data alone, but are distinguishable on infection intensity. We then present a case study to evaluate a previous finding of a positive association between prevalence of a severe avian malaria infection (GRW2, Plasmodium ashfordi) and a major histocompatibility complex (MHC) class I allele (B4b) in great reed warblers Acrocephalus arundinaceus. Using the same dataset, we find that individuals with allele B4b have lower GRW2 infection intensities than individuals without this allele. Therefore, allele B4b provides quantitative resistance rather than increasing susceptibility to infection. This implies that birds carrying B4b can mount an immune response that suppresses the acute-phase GRW2 infection, while birds without this allele cannot and may die. We argue that it is important to determine whether MHC alleles related to infections are advantageous (quantitative and qualitative resistance) or disadvantageous (susceptibility) to obtain a more complete picture of pathogen-mediated balancing selection.

Publishing year

2012

Language

English

Pages

577-584

Publication/Series

Proceedings of the Royal Society B: Biological Sciences

Volume

279

Document type

Journal article

Publisher

Royal Society Publishing

Topic

  • Biological Sciences

Status

Published

Project

  • Avian MHC genes

Research group

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Other

  • ISSN: 1471-2954