Normal aggregations of glycoprotein IV (CD36)-deficient platelets from seven healthy Japanese donors.

Since glycoprotein IV (GPIV) has been shown to play an important role in the interaction of platelets with collagen and thrombospondin, the aggregation and secretion of GPIV-deficient platelets were examined. Using a binding assay with monoclonal 125I-OKM5 antibody against CD36 antigen and crossed immunoelectrophoresis of the solubilized platelets against anti-GPIV antibody, the platelets from seven (4.1%) out of 170 healthy Japanese donors were found to be deficient in GPIV. The GPIV-deficient platelets showed normal aggregations in response to collagen as well as ADP, epinephrine, arachidonic acid and thrombin in comparison with GPIV-positive platelets. Polyclonal anti-GPIV antibody aggregated GPIV-positive platelets but not the GPIV-negative ones. The F(ab')2 fragments of the anti-GPIV antibody competitively inhibited the anti-GPIV-induced aggregation, but did not affect the collagen-induced aggregation of GPIV-positive platelets. These results suggest that the deficiency of GPIV does not affect platelet aggregability.