EVIDENCE FOR AT LEAST 3 TRANSCRIBED BOLA CLASS-I LOCI

Serological data identify a single major histocompatibility complex (M HC) class I locus in cattle. Molecular data, however, demonstrate the presence of at least two cattle MHC (BoLA) class I loci. To investigat e the number of transcribed BoLA class I genes, we amplified cattle cD NA by using a single MHC class I-specific primer that hybridized to a conserved region of exon 4 and a non-specific 3' primer. Six BoLA clas s I cDNAs have been cloned and sequenced from a Bos taurus bull hetero zygous for BoLA class I serological antigens, demonstrating the presen ce of a minimum of three loci. Sequence comparisons suggested that one of these cDNAs may be an unexpressed allele or the product of a noncl assical locus.