The Gerbich blood group system consists of 11 antigens carried on a single pass type I membrane glycoprotein with called glycophorin C (GPC) and/or glycophorin D (GPD). GPC consists of 128 amino acids and GPD, the shorter isoform, has 107 amino acids. The glycoproteins are encoded by GYPC, or GE if analysis is to predict a blood group antigen.