Evolution of the major histocompatibility complex: Molecular cloning of major histocompatibility complex class I from the amphibian Xenopus

Class I major histocopatibility complex (MHC) cDNA clones have been isolated from an expression library derived from mRNA of an MHC homozygous Xenopus laevis. The nucleotide and predicted amino acid sequences show definite similarity to MHC class I molecules of higher vertebrates. The immunoglobulin-likeα-3 domain is more similar to the immunoglobulin-like domains of mammalian class II β chains than to those of mammalian class I molecules, and a tree based on nucleotide sequences of representative MHC genes is presented