Glycophorins A (GPA) and B (GPB) are sialoglycoproteinswith a single pass membrane. Blood group M and Nspecificities are carried by GPA, whereas S and Uspecificities are accounted for by GPB. It has beenproposed that the broad mucin-like surface that GPA andGPB give the cells acts as a barrier to cell fusion, reducingthe amount of aggregation that occurs between red bloodcells in the bloodstream. Glycophorin The formation oferythroid cells and the diagnosis of erythroid leukaemiashave both been described by an antibody.