Glycophorin A on normal and leukemia cells detected by monoclonal antibodies, including a new monoclonal antibody reactive with glycophorins A and B.

A new hemagglutinating monoclonal antibody, MoAb31, detected glycophorins A and B in Western blots. Results with enzyme-modified erythrocytes indicated the MoAb31 determinants were sialic acid dependent, and resided on glycophorin A on the trypsin-resistant, ficin-sensitive segment, and on glycophorin B on the ficin-sensitive segment. Another new monoclonal antibody, MoAb36, detected the Wrb antigen, located on the non-glycosylated segment of glycophorin A near its insertion into the lipid bilayer. Immunofluorescent staining of normal hematopoietic and leukemia cells with these and other monoclonal antibodies to glycophorin A demonstrated glycophorin A on erythroid cells only. Cytofluorograph analysis showed the majority of cells of the erythroleukemia cell lines K562 and HEL expressed glycophorin A, as indicated by reactivity with the monoclonal glycophorin A antibodies R10, R18, 6A7 and 10F7. However, reactivity with monoclonal antibodies to glycosylated determinants (MoAb31 and R1.3) and to the non-glycosylated segment near the membrane insertion (MoAb36, and R7.1) was reduced or absent. Expression of "missing" glycophorin A antigens on K562 and HEL could not be induced using a variety of chemical and biologically active modifiers. We conclude that glycophorin A of erythroleukemia cell lines K562 and HEL differs from glycophorin A at the surface of normal, mature erythrocytes with respect to reactivity with monoclonal glycophorin A antibodies.