Characterization of a monoclonal antibody which is an activator of rabbit platelets.
A monoclonal antibody (MAb) raised against rabbit platelet membranes was shown to be a strong agonist to induce platelet aggregation and secretion. This MAb, designated 19CB-1, was identified as an IgM and purified to near homogeneity by ammonium sulfate precipitation and Q-sepharose column chromatography. Aggregation induced by 19CB-1 was only slightly affected in the presence of creatine phosphate/creatine phosphokinase and aspirin, indicating that it was not mediated through the cyclooxygenase pathway and the release of ADP. 19CB-1 Fab fragments did not induce platelet aggregation. However, 19CB-1-induced aggregation was inhibited by these Fab fragments. 19CB-1 also elicited a rise in cytoplasmic calcium concentration in fura-2 loaded platelets. In the absence of external calcium, a substantial calcium signal remained to be observed, suggesting the release of calcium from intracellular stores in response to 19CB-1. This MAb reacted primarily with a polypeptide of Mr = 57,000, as revealed by immunoblotting. These results suggest that the 57 kDa antigen is one of the platelet surface proteins directly involved in the activation of rabbit platelets.
Chau
L Y
LY
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, China.
Lin
J R
JR
D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D000954:Antigens, Surface / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D015151:Immunoblotting; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D015539:Platelet Activation; D010974:Platelet Aggregation; D011817:Rabbits
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D007140:Immunoglobulin Fab Fragments; D000244:Adenosine Diphosphate; D002118:Calcium