Heterodimer with B2M. Detected in skin, esophagus, tongue, skin, muscle, uterus, ovary, testis and epididymis. In neonatal animals, highly expressed in skin. Belongs to the MHC class I family. Lacks key residues involved in peptide docking, suggesting that this is a non-classical MHC class I protein which does not play a role in antigen presentation.