The major histocompatibility class II alpha chain in salmonid fishes

In this study the characterisation of the Atlantic salmon (MhcSasa-DAA) and rainbow trout (MhcOnmy-DAA) class II alpha chain cDNA sequences is present ed. The DAA sequences from these two salmonid species showed a high degree of similarity, although the Ommy-DAA*03 cDNA sequence differed in the cytop lasmic region. Interestingly, the Onmy-DAA*02 sequence has lost tho second cysteine in the alpha-1 domain. However, another cysteine is present in thi s sequence 7 positions downstream of the cysteine which is substituted for a leucine. Despite a thorough search, only a single locus of expressed clas s II alpha chain sequences was identified in both salmonid species. Amplifi cation by PCR and sequencing of the alpha-1 domain from genomic DNA of thre e Atlantic salmon, identified four different variants assumed to have deriv ed from this single locus. Two of these variants originated from one indivi dual and are likely functional alleles, (C) 2000 Elsevier Science Ltd. All rights reserved.