Specificity of autoantibodies in autoimmune thrombocytopenia

Abstract

In 42 patients with autoimmune thrombocytopenia (AITP) and a positive direct platelet suspension immunofluorescence test (PSIFT), the antigenic specificity of the autoantibodies was studied. Because the autoantibodies were often not detectable in the serum and additional HLA antibodies may disturb the reaction pattern with the platelet panel, we used eluates prepared from the patients' platelets for this study. Thirty-five patients had antibodies equally reactive with normal platelets, irrespective of their antigenic make-up, but not with the platelets from two Glanzmann's disease patients. Absorption and elution experiments in two patients showed that his was probably not due to the presence of a combination of anti-Zwa and anti-Zwb antibodies. Thus, the majority of autoantibodies against platelets seems to be directed against antigenic determinants not present on Glanzmann's disease platelets, but perhaps located on the platelet-membrane glycoproteins IIb and/or IIIa. In ten patients, antibodies of no, or still unknown, specificity were detected. Three of these had additional antibodies not reactive with the platelets of the two Glanzmann patients.

The pathogenesis of immune thrombocytopaenic purpura

“…The specificity of the antiplatelet antibodies to individual platelet glycoproteins (GP), such as GPIIb/IIIa, was demonstrated by van Leeuwen et al (1982) using the platelet immunofluorescent test (PIFT). In 32 of 42 cases, platelet IgG eluated from patients with ITP bound to normal platelets but not to platelets from patients with Glanzmann's thrombasthenia, who lack platelet GPIIb/IIIa.…”

Acquired thrombasthenia due to GPIIbIIIa platelet autoantibodies in a 4‐yr‐old child

“…In the case described here, there was no clinical or radiological evidence of malignancy, an autoantibody screen was negative; the remainder of the blood count, lymphocyte subset analysis, serum immunoglobulin and complement levels were within the normal range. In autoimmune thrombocytopenia (AITP), platelet associated immunoglobulin is frequently directed against GPIIbIIIa or other major platelet membrane GPs (4). The autoantibodies involved in AITP are generally IgG (5), predominantly IgG1 ± IgG3 (6).…”

Rare complication of treated immune thrombocytopenia

“…GPIIb/IIIa is the most densely expressed glycoprotein on the platelet surface and serves as the receptor for fibrinogen, making it one of the key players in platelet aggregation . Autoantibodies directed against GPIIb/IIIa in ITP patients were first described by van Leeuwen et al ., and the first case of AGT was described by Greaves et al Patients with AGT can have bleeding despite normal platelet counts or may present with bleeding which is disproportionate to the platelet count . It is seen in association with autoimmune disorders, lymphoproliferative disorders or use of certain medications .…”