Activation of human platelets by the rabbit anticardiolipin antibodies.
Affinity purified anticardiolipin antibodies (ACLA) raised in rabbits showed cross-reactivities with various negatively charged phospholipids as shown by both the solid phase enzyme-linked immunosorbent assay (ELISA) and inhibition studies. In ELISA, ACLA showed strong cross-reactivity to both sphingomyelin (SM) and phosphatidylethanolamine (PE), but the inhibition studies showed that ACLA failed to bind the aqueous suspensions of SM, PE, and PE/PC (1:1). ACLA bound to resting gel-filtered human platelets (GFP) as shown by both inhibition study and flow cytofluorometric analysis. Western blotting procedure showed that ACLA strongly cross-reacted to an 80-Kd plasma membrane protein. ACLA activated platelet response in a concentration-dependent manner. At less than 10 micrograms/mL, ACLA induced both platelet shape change to spiculate irregular forms as shown by scanning electron microscopy and the phosphorylation of 20-Kd protein. ACLA at more than 10 micrograms/mL caused platelet aggregation and secretion. The aggregation was inhibited by EDTA; aspirin; antimycin A plus 2-deoxyglucose; PGE1; and the F(ab')2 fragment of ACLA. It was not inhibited by monoclonal antibody to Fc receptor (MoAb FcR2). The biochemical events of ACLA-induced platelet response involved the elevation of (1) thromboxane A2 formation, (2) cytosolic free calcium ion concentration ([Ca2+]i), and (3) 47-Kd protein phosphorylation. In addition, the subaggregatory concentration of ACLA showed synergistic platelet activation with that concentration of thrombin, collagen, and epinephrine. The study showed the mechanism involved in ACLA-induced platelet responses.
Lin
Y L
YL
Institute of Life Science, National Tsing Hua University, Hsinchu, Taiwan.
Wang
C T
CT
D000818:Animals; D017153:Antibodies, Anticardiolipin / Q000494:pharmacology*; D000936:Antigen-Antibody Complex; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D002118:Calcium / Q000097:blood; D003094:Collagen / Q000494:pharmacology; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D007136:Immunoglobulins / Q000302:isolation & purification; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D010743:Phospholipids / Q000494:pharmacology; D010750:Phosphoproteins / Q000097:blood; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects / Q000276:immunology*; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits / Q000276:immunology; D012701:Serotonin / Q000097:blood; D013917:Thrombin / Q000494:pharmacology; D013929:Thromboxane B2 / Q000097:blood
D017153:Antibodies, Anticardiolipin; D000936:Antigen-Antibody Complex; D007140:Immunoglobulin Fab Fragments; D007136:Immunoglobulins; D010743:Phospholipids; D010750:Phosphoproteins; D012701:Serotonin; D013929:Thromboxane B2; D003094:Collagen; D013917:Thrombin; D002118:Calcium; D004837:Epinephrine