Molecular polymorphism and expression analysis of MHC class II B gene from red sea bream (Chrysophrys major)

MHC class 11 (major histocompatibility complex class 11) plays an important role in the immune response of vertebrates. Its function is to present antigenic peptides to the T-cell receptor. In order to study the function and molecular polymorphism of class 11 B gene in fish, we have isolated cDNAs encoding class 11 B from spleen cDNA library of red sea bream (Chrysophrys major) by using EST sequencing, and examined genomic organization, molecular polymorphism and expression of red sea bream class 11 B gene. As in other vertebrates, five exons and four introns were identified in red sea bream class 11 B gene. Seven class 11 B alleles were identified from seven individuals of red sea bream. The deduced amino acid sequence of red sea bream MHC class 11 B I(Chma-DAB*0101) had 87.1, 85.1, 87.1, 90.4, 87.1. 90.8% identity with those of red sea bream class 11 B 2, 3, 4,5, 6,7(Chma-DAB*0201-Chma-DAB*0701), respectively, and had 75.2,74.5,55.9,55.1,34.3 and 30.4% identity with those of striped sea bass, cichlid, rainbow trout, Atlantic salmon, mouse and human, respectively. Four different class 11 B alleles were observed in a single individual and two different 3' untranslated region (3' UTR) sequences from this individual may infer the existence of two loci at least. Semi-quantitative RT-PCR demonstrated that high expression was detected in liver, head kidney, kidney, intestine, gill, stomach, hear and spleen, low expression in muscle and blood. Challenue of red sea bream with the pathogenic bacteria, Vibrio anguillarum, resulted in a significant decrease in the expression of MHC class H B mRNA from 5 to 72 h after infection in liver, spleen, head kidney and intestine, followed by a recovery to normal level after 96 h, (c) 2005 Elsevier Ltd. All rights reserved.