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| Major histocompatibility complex class II antigens are important in vertebrate immune system. In the present study, the full length cDNA sequence of class II A gene was got by RACE-PCR from half-smooth tongue sole (Cynoglossus semilaevis), and its open reading frame (ORF) polymorphism was studied. The whole cDNA sequence was 992 bp in length, including the ORF of 717 bp. Twenty-five alleles were identified and clustered into two distinct groups for the specific nucleotides/ amino acids in specific positions, so they belonged to two class II A genes and dominated as Cyse-DAA and Cyse-DBA with 11 and 14 alleles respectively. Four Cyse-DAA alleles were observed in one individual, and three to five Cyse-DBA alleles in each of three detected individuals, which indicated that at least two loci existed in each gene. Moreover, in order to study the association of the alleles of A genes and resistance to infection, 200 individuals were intraperitoneally injected with Vibrio anguillarum and the first 20 dead individuals and 20 surviving ones were selected for genotypes of A genes. Fifty-six alleles were identified among the 40 individuals, 29 of which belonged to Cyse-DAA and 27 belonged to Cyse-DBA. Eighteen alleles were selected for the association study between alleles and resistance to infection. Though not significant, allele Cyse-DAA*0201, Cyse-DAA*1101, Cyse-DBA*0401, Cyse-DBA*1102, Cyse-DBA*1801 and Cyse-DBA*2201 appeared only in surviving individuals, while allele Cyse-DAA*0901, Cyse-DBA*1101 and Cyse-DBA*1401 occurred more frequently in dead individuals. This study confirmed the existence and polymorphism of two class II A genes and also the association between alleles of class II A genes and disease susceptibility/ resistance in half-smooth tongue sole. |
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| Keywords:Genetics; MHC II A; Cynoglossus semilaevis; Vibrio anguillarum |
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