We evaluated the presence of anti-glycoprotein (GP) Ib antibodies in the plasma from chronic idiopathic thrombocytopenic purpura (ITP) using micro-enzyme-linked immunosorbent assay (micro-ELISA). Microtiter wells coated with monoclonal anti-GP Ib antibody, OP-72, were incubated with platelet lysate and washed to purify and immobilize GP Ib. The well-bound GP Ib was incubated with patient or control plasma and antibodies bound to the well were quantitated with alkaline phosphatase conjugated anti-human IgG.
Three of the 87 patients with chronic ITP and one of the 17 patients with SLE had anti-GP Ib antibodies in their plasma. However, none of 12 patients with aplastic anemia had anti-GP Ib antibodies. Reactivity of the antibodies in the three ITP plasmas against GP Ib was also demonstrable by immunoblot procedure. Furthermore, the antibody from one patient reacted with patient's own platelet GP Ib. These data indicated that some patients with ITP have autoantibodies against GP Ib.
