Clinical Significance and Detection of Antibodies Against Platelet GP Ib/I X and Gp II b/IIIa in Childhood Chronic Idiopathic Thrombocytopenic Purpura

Kim, Kir Young; Park, Sae Myung; Yang, Chang Hyun; Lyu, Chuhl Joo; Cho, Hyun Sang; Oh, Seung Hwan; Kim, Hyun Ok

Abstract

BACKGROUND: Chronic idiopathic thrombocytopenic purpura is an autoimmune disorder caused by sequestration of antibody-sensitized platelets in the reticuloendothelial system. However, uncertainty as to the specificity, frequency and clinical significance of such antibodies still remains. So, we tried to further clarify the above uncertainty in childhood chronic idiopathic thrombocytopenic purpura.
METHODS
We analyzed sera from 29 patients. Twenty six patients were chronic ITP who were admitted or followed up to the Department of Pediatrics, Severance Hospital, Yonsei University Medical College from August 1996 to March 1997 by employing a modified antigen-capture ELISA(MACE), flow cytometry and electrophoresis(SDS-PAGE) and immuno-blotting(IB) assays. Three patients with ITP less than 6 months after onset of ITP were included to know the possibility to differrentiate between acute ITP and chronic ITP in this study.
RESULTS
1) Glycoprotein(GP)-specific antibodies were found in 28% (8/29) of patients, with 2 patients having antibodies directed solely to Gp II b/III a, no patients holding antibodies specific only for GPI b/I X and 6 possessing antibodies against both anti-GP I b/I X and Gp II b/III a antigen. 2) The detection rate of GP-specific antibodies of flow cytometry was about 10%. The positivity of anti-GPI b/I X antibodies by MACE and immunoblotting was 14% (4/29), respectively, the positivity of anti-Gp II b/III a antibodies by MACE and immunoblotting was, 21 % (6/29) respectively. The concordance rate between two assays(MACE and IB) was 79% (23/29). None of the three methods was good enough to stand alone. 3) Serum antibodies were not more frequently detected in active(p=1.0) or non-splenectomized(p=.54) chronic ITP patients. 4) No association was found between antibody specificity(anti-GPI b/I X, anti-Gp II b/ III a) and platelet counts(p : .87).
CONCLUSION
We conclude that in korean childhood chronic ITP, antibodies against both anti-GPI b/I X and Gp II b/III a antigen were predominant antibody. But, the longterm follow-up in more cases is needed to further clarify the clinical significance of antral-platelet antibody in chronic ITP should be assessed.