Properties of the blood group LW glycoprotein and preliminary comparison with Rh proteins

The major component immunoprecipitated from human red cell membranes by murine monoclonal antibodies (BS46 and BS56) against the LW blood group antigens is a 42,000 mol. wt glycoprotein. Upon digestion by an N-glycanase the LW component migrated as a 25,000 mol. wt component on SDS gels, whereas treatment by an O-glycanase led only to a small size reduction (2000). These data suggest that the LW glycoprotein might carry approximately eight to nine N-linked sugar chains and only a few (one or two) O -linked oligosaccharide chains. A minor component of 31,000 mol. wt was also identified in the LW immunoprecipitate. Preliminary analyses by two-dimensional peptide mapping indicate that the 31,000 mol. wt polypeptide is identical to authentic Rh proteins, therefore raising the possibility that the Rh and LW antigens are associated in the membrane as a functional complex called Rh cluster. Since the W-deglycosylated form of the LW and RhD proteins have different sizes (25,000 vs 31,000–32,000 respectively) and since their externally 125I-labelled domains have different two-dimensional peptide maps, it is concluded that LW is probably not a simple glycosylated form of the Rh proteins.