Presence of P blood group antigens on human platelets

Except for ABH antigens, the presence of red cell (RBC) antigens on human platelets has been a source of disagreement among investigators. Because ABH antigens share precursor sequences with P-system saccharides, the authors examined human platelets for evidence of P blood group antigens. Anti-P was directly labeled with 125I and incubated with normal platelets in a one-stage radioimmunoassay (RIA). Alternatively, platelets from donors of known RBC phenotype were incubated with anti-P, anti-P1, or anti-Tja, washed, incubated with FITC-labeled goat anti-human immunoglobulin and evaluated by fluorescence flow cytometry. The results of these assays demonstrate that platelets express P blood group antigens in parallel to the donor's RBCs. The role of these antigens in platelet transfusion is not known.