Evidence for an expression of blood group A antigen on platelet glycoproteins IV and V

Blood group ABO antigens are known to be carried by several platelet glycoproteins (GP), e.g. GPIb, GPIIa, GPIIb, GPIIIa and PECAM. Beside these proteins, we recently observed that blood group A antigen was also expressed on some other uncharacterized platelet proteins (70-90 kDa) having electrophoretic mobilities closely resembling those of GPIV and GPV. These findings prompted us further to characterize these latter ABO-expressing platelet proteins. By antigen capture ELISA, wherein the monoclonal antibodies (mAbs) CLB-IVC7 and CLB-SW16 were used to hold the corresponding antigens GPIV and GPV, human anti-A specifically bound to these proteins derived from Al-platelets; neither GPIV nor GPV derived from A(2)-, B- or O-platelets bound anti-A. In a Western blot assay using immunoprecipitated GPIV and GPV as antigens, mAb anti-A immunostained GPIV and GPV precipitated from A(1), but not from A(2) and O platelets. These results conclusively demonstrate that blood group A antigen is expressed on platelet GPIV and GPV.