Study of Autoantibodies Against Platelet GP IIb/IIIa and GP Ib/IX in Childhood Chronic Idiopathic Thrombocytopenic Purpura

Woo, Chanwook; Lee, Junghwa; Lee, Kwangchul; Kim, Soonkyum

Abstract

PURPOSE: Chronic idiopathic thrombocytopenic purpura (CITP) is an autoimmune disease caused by autoantibodies reacting to certain antigens, and platelet glycoprotein (GP) IIb/IIIa and GP Ib/IX complexes are thought to be some of those antigens. However, the clinical significance of anti-GP autoantibodies in CITP patients is unknown. In this study, we investigated the clinical correlation between the presence of circulating autoantibodies against GP IIb/IIIa and GP Ib/IX, and disease activity. MEHTODS: From December 1997 to June 1998, 20 CITP patients were enrolled in this study. Autoantibodies against GP IIb/IIIa and GP Ib/IX in patient's sera during treatment were detected by immunoblotting, and their platelet counts at the initial evaluation and 6 month follow-up were compared according to the presence or the absence of antibodies.
RESULTS
Autoantibodies to GP antigens were found in 40% (8/20) of the patients. Seven patients were positive for GP IIb/IIIa; 4 for GP Ib/IX and 3 for both. GP autoantibody-positive patients had lower mean platelet counts than GP autoantibody-negative patients at initial evaluation (133,000/microliter vs 172,000/microliter, P>0.05) and at 6 month follow-up (154,000/microliter vs 192,000/microliter, P>0.05). Detection of GP autoantibodies related more with active disease than with remission at initial evaluation (45.5%(5/11) vs 33.3%(3/9), P>0.05) and at 6 month follow-up (50.0%(5/10) vs 30.0% (3/10), P>0.05). There was no detection of GP-specific antibodies in 3 splenectomized patients.
CONCLUSION
It is hard to conclude on our data alone that the presence of GP autoantibodies correlates with disease status in CITP, although it seems to associate with lower platelet counts.