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Experimental evidence for major histocompatibility complex-allele-specific resistance to a bacterial infection

Author

Summary, in English

The extreme polymorphism found at some major histocompatibility complex (MHC) loci is believed to be maintained by balancing selection caused by infectious pathogens. Experimental support for this is inconclusive. We have studied the interaction between certain MHC alleles and the bacterium Aeromonas salmonicida, which causes the severe disease furunculosis, in Atlantic salmon (Salmo salar L.). We designed full-sibling broods consisting of combinations of homozygote and heterozygote genotypes with respect to resistance or susceptibility alleles. The juveniles were experimentally infected with A. salmonicida and their individual survival was monitored. By comparing full siblings carrying different MHC genotypes the effects on survival due to other segregating genes were minimized. We show that a pathogen has the potential to cause very intense selection pressure on particular MHC alleles; the relative fitness difference between individuals carrying different MHC alleles was as high as 0.5. A co-dominant pattern of disease resistance/susceptibility was found, indicative of qualitative difference in the immune response between individuals carrying the high- and low-resistance alleles. Rather unexpectedly, survival was not higher among heterozygous individuals as compared with homozygous ones.

Publishing year

2002

Language

English

Pages

2029-2033

Publication/Series

Royal Society of London. Proceedings B. Biological Sciences

Volume

269

Issue

1504

Document type

Journal article

Publisher

Royal Society Publishing

Topic

  • Ecology
  • Biological Sciences

Status

Published

Research group

  • Molecular Ecology and Evolution Lab

ISBN/ISSN/Other

  • ISSN: 1471-2954