A monoclonal antibody (LK-4) which differentiates PLA1 from PLA2 platelet extracts but not intact platelets

Abstract A unique murine monoclonal antibody (LK-4) is described which differentiates PLA 1 /PLA 1 platelet extracts from PLA 2 /PLA 2 and PLA 1 /PLA 2 platelet extracts on solid phase ELISA and immunoblot at the 100kD GPIIIa location, but not on intact platelets. LK-4 reacts equally with intact PLA 1 /PLA 2 and PLA 2 /PLA 2 platelets. Adsorbtion of LK-4 with PLA 1 /PLA 1 platelets results in loss of reactivity for intact platelets as well as platelet extracts on ELISA or immunoblot. LK-4 inhibits platelet aggregation induced by ADP, epinephrine, collagen and thrombin, suggesting reactivity at or near the fibrinogen binding site on GPIIIa. It is suggested the LK-4 reacts with a conformation-induced common epitope for PLA 1 and PLA 2 on GPIIIa, with loss of this conformation for PLA 2 GPIIIa following solubilization with Triton X-100.