ISOLATION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II BETA-SEQUENCE FROM LAKE-TANA PARREL (BARBUS-INTERMEDIUS COMPLEX)

Ther are at least fourteen different morphotypes of large barbel (Barb us intermedius spp.) in Lake Tana (Ethiopia). This diversity might be the result of a major adaptive radiation in the last 2.5 million years . The major histocompatibility complex (MHC) contains loci encoding pr oducts involved in antigen presentation that are instrumental in the s pecific activation of the cognate immune system and are the most polym orphic known in warm blooded vertebrates. In humans, the MHC class II genes can have up to 40 alleles. The polymorphic nature of these allel es allows them to be used for phylogenetic analyses. Polymerase chain reaction primers specific for the MHC class II gene, McdCyca-DAB, from the common carp (Cyrpinus carpio) have been used to amplify the first intron and second exon of this gene from Barbus DNA, The second exon encodes the peptide binding region - the region that shows the highest polymorphism between alleles. Intron sequences obtained from three mo rphotypes within the lake (''acute'', ''intermedius'' and ''lip''), as well as one Portuguese Barbus bocagei individual, have been used in p hylogenetic analyses. The Barbus sequences group together on a branch separate from the Cyca sequences. Further analyses of sequences obtain ed from different morphotypes might aid in determining the relationshi p between these morphotypes.