Cloning and characterization of ovine β2-microglobulin cDNAs

Beta-2-microglobulin (β2m) is the light chain of the major histocompatibility complex (MHC) class I cell surface heterodimer. β2m is well conserved across most species with few polymorphisms seen within species. The aims of this study were to clone and express ovine β2m and investigate if allelic variation of ovine β2m exists. Ovine β2m clones were isolated from five sheep of three breeds by reverse-transcription polymerase chain reaction (RT-PCR). Sequence analysis showed that four ovine β2m sequences were obtained. Within breeds and individual animals there was evidence of allelic variation of ovine β2m. An expression system was established to express one of the alleles with an ovine MHC class I cDNA clone in human embryo kidney cells (HEK293) and quail cells (QT35). Transfection experiments showed that ovine β2m was expressed and directed the expression of ovine MHC class I heavy chain to the cell surface of the transfected cells. Both bovine and human β2m supported ovine MHC class I heavy chain cell surface expression.