Immunopurification of the blood group RhD protein from human erythrocyte membranes

Rh proteins are membrane proteins encoded by genes at the blood group RH locus. They are of paramount importance in transfusion medicine, but their function is still unknown. Biochemical and biophysical studies of these proteins are scarce since only minute amounts of the very hydrophobic Rh proteins, can be purified from human erythrocytes. Recently, a human monoclonal antibody (LOR-15C9) was described as having the unique property to recognize the Rh30 protein carrying the major blood group D specificity (RhD protein), either in a membrane detergent extract or when blotted on a membrane. In this report, we describe one-step purification of the RhD protein from detergent extracts of red cell membranes, based on immunoaffinity chromatography carried out with immobilized LOR-15C9 IgG. The technique yielded RhD protein with high purity which was devoid of other associated proteins (RhAG, CD47, LW and GPB) that comprise the Rh complex in the erythrocyte membrane. By contrast immunoprecipitation performed with the same antibody led to co-isolation of both RhD and RhAG.