Binds to heparan sulfate proteoglycans on the surface of fibroblast (NIH-3T3) cells. Heterodimer with B2M (beta-2-microglobulin). Ubiquitously expressed in neonatal and adult tissues. N-glycosylated. Belongs to the MHC class I family. Lacks key residues involved in peptide docking and also does not require TAP (transporter involved in antigen processing) for cell surface expression, suggesting that this is a non-classical MHC class I protein which does not play a role in antigen presentation.