Further Studies on a Specific Platelet Antibody Found in Bernard‐Soulier Syndrome and its Effects on Normal Platelet Function

Summary. An IgG antiplatelet antibody found in a multitransfused patient with Bernard‐Soulier syndrome (BSS), reacted with a normal platelet surface antigen of 150 000 daltons which was similar to the glycoprotein missing from BSS platelets. The BSS platelet antibody (BSS‐Pab) aggregated all control platelets which then released ADP and 5‐HT and synthesized thromboxane. When mixed with the antibody, BSS platelets did not aggregate, did not release ADP and 5‐HT and failed to synthesize thromboxane. The BSS‐Pab was not inactivated by incubation with BSS platelet stroma. While the antibody did not aggregate thrombasthenic platelets, its aggregating activity was lost after incubation with their stroma. The BSS‐Pab did not provoke ADP or 5‐HT release or thromboxane synthesis in thrombasthenic platelets or in the platelets of a patient with platelet cyclooxygenase deficiency or in normal platelets treated with indomethacin. The aggregating, release and synthetic responses of platelets after binding of BSS‐Pab to its membrane antigen (probably glycoprotein I) requires the presence of glycoprotein IIb and/or IIIa and the normal metabolism of arachidonic acid.