Immunoglobulin isotypes in Atlantic salmon, Salmo salar
1Department of Biology (BIO), High Technology Center, University of Bergen, Bergen N-5020, Norway. ivar.hordvik@bio.uib.no.
Biomolecules
|March 4, 2015
Summary
Atlantic salmon possess unique immunoglobulin (Ig) heavy chain gene complexes due to genome duplication. This study details the IgM, IgD, and IgT isotypes, highlighting IgM variants and IgT
Area of Science:
- Immunology
- Genomics
- Aquatic Animal Health
Background:
- Salmonid fish, including Atlantic salmon (Salmo salar), have three major immunoglobulin (Ig) isotypes: IgM, IgD, and IgT, defined by their heavy chains.
- Whole genome duplication in salmonids resulted in two highly similar Ig heavy chain gene complexes (A and B) in Atlantic salmon.
- These complexes contain multiple genes for IgM, IgD, and IgT, including pseudogenes.
Purpose of the Study:
- To characterize the immunoglobulin heavy chain gene complexes in Atlantic salmon.
- To investigate the distinct sub-populations of serum IgM (IgM-A and IgM-B) and their properties.
- To elucidate the specialized role of IgT in mucosal immunity and compare its serum concentration with IgM.
Main Methods:
- Analysis of immunoglobulin heavy chain gene complexes (A and B) in Atlantic salmon.
- Characterization of the structural differences between IgM-A and IgM-B variants.
- Quantification of IgT and IgM levels in serum and comparison of their concentrations.
Main Results:
- Atlantic salmon possess two distinct IgM sub-variants, IgM-A and IgM-B, arising from different μ genes.
- IgM-B exhibits an additional cysteine residue and increased disulfide cross-linking compared to IgM-A.
- The typical serum ratio of IgM-B to IgM-A is 60:40, with variations observed; IgT is significantly less abundant in serum than IgM and specialized for mucosal immunity.
Conclusions:
- The dual Ig heavy chain gene complexes in Atlantic salmon contribute to the diversity of their immunoglobulin repertoire.
- Distinct IgM variants likely play specialized roles in the immune response.
- IgT is confirmed as a key player in mucosal immunity in salmonids, with low serum prevalence.
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