The production of human monoclonal antiplatelet auto‐antibodies derived from human lymphocytes of normal origin: reactivity to DNA, anionic phospholipids and platelet proteins

Human hybridoma monoclonal antiplatelet antibodies were produced using tonsillar lymphocytes from a nonthrombocytopenic male fused to the lymphoblastoid cell line GM 4672. Twenty of 472 (4%) IgM producing hybridomas had antiplatelet reactivity as detected by ELISA. Thirteen of these antiplatelet antibody producing hybridomas with clonality ensured by limiting dilution were tested for antigenic specificity. Two different and mutually exclusive groups of antiplatelet antibodies were identified. The first group of antiplatelet antibodies (four clones) showed reactivity that was limited to DNA and anionic phospholipids. Antibodies from the second group (seven clones) showed reactivity by immunoblotting to a variety of platelet proteins including platelet glycoprotein IIb. These antibodies did not bind DNA nor anionic phospholipids. These studies indicate that lymphocytes of normal human origin have the genetic potential to produce antiplatelet autoantibodies. These antiplatelet antibodies segregate on the basis of their target antigens into two major groups, which mimic the target antigens held responsible for antiplatelet autoantibodies in disease. These include glycoproteins (typical of chronic idiopathic thrombocytopenic purpura) and DNA and/or anionic phospholipids (typical of the lupus anticoagulant syndrome).