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Polymorphism of chicken CD8-alpha, but not CD8-beta
M Luhtala1, C A Tregaskes, J R Young
1Turku Immunology Centre and Department of Medical Microbiology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
Immunogenetics
|September 1, 1997
Summary
Chicken CD8A gene variations drive structural differences, impacting antibody binding. This CD8A polymorphism, unlike CD8B, suggests unique evolutionary paths for these immune genes in chickens.
Area of Science:
- Immunogenetics
- Molecular Biology
- Avian Immunology
Background:
- Chicken CD8 is a crucial T-cell co-receptor.
- Polymorphism in immune genes can influence disease resistance.
- Understanding CD8 structure is key to avian immune responses.
Purpose of the Study:
- To elucidate the structural basis of CD8 polymorphism in chickens.
- To identify specific genetic changes in CD8A and CD8B genes.
- To determine the functional impact of CD8A variations on antibody binding.
Main Methods:
- Comparative nucleotide sequencing of CD8A and CD8B cDNA from three chicken strains.
- Site-directed mutagenesis and cDNA expression in COS cells.
- Monoclonal antibody binding assays.
Main Results:
- Fourteen nucleotide differences in CD8A cDNA led to eight amino acid substitutions in the extracellular domain.
- CD8B showed minimal variation with two amino acid and four silent mutations.
- CD8A substitutions, particularly in the IgV-like and MHC binding regions, determined monoclonal antibody binding specificity.
- No CD8A polymorphism has been reported in other species.
Conclusions:
- Chicken CD8A polymorphism is extensive and structurally significant.
- Amino acid changes in CD8A are solely responsible for differential antibody binding.
- CD8A and CD8B likely evolved under distinct selective pressures in chickens.