Characteristics of platelet aggregation induced by the monoclonal antibody ALB6 (acute lymphoblastic leukemia antigen p 24). Inhibition of aggregation by ALB6Fab.

The leukemia-associated cell surface antigen p 24 is found on normal platelets as well as on Bernard Soulier syndrome and thrombasthenia type I platelets. ALB6 IgG (a monoclonal antibody against p 24) induces the aggregation of platelets from normal donors but not from thrombasthenia. In contrast, ALB6 Fab inhibits platelet aggregation induced by collagen, ADP, thrombin, ionophore A 23187 and ALB6 IgG. The results suggest that ALB6 interferes with a mechanism common to all aggregation pathways; the possible mechanisms are discussed.