22953 Platelet Autoantibody, Cell Bound (CBPAN)

Platelet antibodies may be allo- or autoantibodies and may be directed to a wide range of antigenic "targets" on platelet cytoplasmic membranes. Alloantibodies are involved in clinical conditions such as platelet refractoriness, neonatal alloimmune thrombocytopenia, and posttransfusion purpura. In contrast, platelet autoantibodies are involved in idiopathic (autoimmune) thrombocytopenic purpura, the thrombocytopenia associated with systemic lupus erythematosus, and with the thrombocytopenia associated with sepsis (usually bacterial, occasionally fungal). Sometimes platelet autoantibodies can be detected in the patient's serum, but extensive data demonstrate that direct detection of immunologically bound immunoglobulin (usually IgG) is considerably more sensitive for autoantibody detection. The method consists of an elution step followed by solid-phase enzyme-linked immunoassay, which not only concentrates the cell-bound antibodies, but identifies the target glycoproteins against which they are directed. In most studies of autoimmune thrombocytopenia, the majority (approximately 80%) of detected autoantibodies were directed to the platelet glycoprotein IIb/IIIa and, more rarely, to other glycoproteins such as Ib/IX (approximately 11%) or Ia/IIa.

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