Further studies on a specific platelet antibody found in Bernard-Soulier syndrome and its effects on normal platelet function.

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 IIa and the normal metabolism of arachidonic acid.