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United States Department of Agriculture

Agricultural Research Service

Title: Analysis of Diversity in B-Fii and B-Fiv Chicken Class I Alleles

Authors
item Hunt, Henry
item Fulton, Janet - HY-LINE INTERNATIONAL

Submitted to: Journal of Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 21, 1997
Publication Date: N/A

Interpretive Summary: This paper identifies differences in the genetic code of regions which influence disease resistance in chickens. The genetic differences identified will be used by basic and applied (industry) scientists to design more precise approaches for the identification of disease resistant traits. This information will be used to develop molecular and serologic test kits for quicker, less expensive and more precise analysis of the genetic diversity in both commercial and experimental flocks. The pattern of genetic diversity identified will provide new insight and improved strategies to increase natural disease resistance in chickens.

Technical Abstract: Twenty-eight Mhc class I (F) cDNA sequences, isolated from 21 different lines of chickens, were analyzed at the molecular level. The 21 different chicken lines include different Mhc (B) congenic lines homozygous for Rfp-Y as well as lines fixed for the B complex but segregating for different Rfp-Y haplotypes. The F cDNA sequences isolated from these lines group into two nodes based on Pileup analysis. The two F nodes display 10 locus specific nucleotide position, however, both inter- and intra-locus recombination is also evident. The DNA sequence of both F nodes are polymorphic in different B congenic haplotypes fixed for Rfp-Y. Conversely, F cDNA isolated from chicken lines fixed for the B haplotype but segregating for different Rfp-Y haplotypes are not polymorphic. Based on this analysis, these two nodes have been assigned to the B-FII and B-FIV loci located in the B complex and do not appear to be expressed by F loci in the Rfp-Y complex. The B-FIV node is highly polymorphic in the exons 2 and 3 encoding the peptide binding site while B-FII is less polymorphic in this region. Previously identified serologic epitopes show the B-FII21 cDNA does not express a class I protein product. This suggests that B-FII represents a pseudogene with little or no antigen presenting function. The region encoding the B-FIV alpha 2 helix has an altered replacement to silent substitution ratio compared to mammalian class I. This altered ratio creates a relatively monomorphic helix with regard to amino acid residues predicted to interact with the T cell receptor. Co-evolution between the antigen presenting and T-cell receptor loci is discussed.

Last Modified: 7/22/2014
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