Unraveling the evolution of the Atlantic cod's (Gadus morhua L.) alternative immune strategy

PLoS One. 2013 Sep 3;8(9):e74004. doi: 10.1371/journal.pone.0074004. eCollection 2013.


Genes encoding the major histocompatibility complex (MHC) have been thought to play a vital role in the adaptive immune system in all vertebrates. The discovery that Atlantic cod (Gadus morhua) has lost important components of the MHC II pathway, accompanied by an unusually high number of MHC I genes, shed new light on the evolution and plasticity of the immune system of teleosts as well as in higher vertebrates. The overall aim of this study was to further investigate the highly expanded repertoire of MHC I genes using a cDNA approach to obtain sequence information of both the binding domains and the sorting signaling potential in the cytoplasmic tail. Here we report a novel combination of two endosomal sorting motifs, one tyrosine-based associated with exogenous peptide presentation by cross-presenting MHCI molecules, and one dileucine-based associated with normal MHC II functionality. The two signal motifs were identified in the cytoplasmic tail in a subset of the genes. This indicates that these genes have evolved MHC II-like functionality, allowing a more versatile use of MHC I through cross-presentation. Such an alternative immune strategy may have arisen through adaptive radiation and acquisition of new gene function as a response to changes in the habitat of its ancestral lineage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biological Evolution*
  • DNA Primers
  • Gadiformes / genetics
  • Gadiformes / immunology*
  • Histocompatibility Antigens Class I / chemistry
  • Histocompatibility Antigens Class I / classification
  • Histocompatibility Antigens Class I / genetics*
  • Histocompatibility Antigens Class II / chemistry
  • Histocompatibility Antigens Class II / classification
  • Histocompatibility Antigens Class II / genetics*
  • Molecular Sequence Data
  • Phylogeny
  • Polymerase Chain Reaction
  • Sequence Homology, Amino Acid


  • DNA Primers
  • Histocompatibility Antigens Class I
  • Histocompatibility Antigens Class II

Grant support

Supported by Norwegian Research Council grant# 187940/S10 and University of Oslo, EMBIO. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.