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Increase of C3a is Associated with Hemorrhagic Propensity in Patients with Immune Thrombocytopenia by Jian Ge, Lihong Wang, Jing Li, Yan Hu, Qianfei Xu, Yang Chen, Ruiqin Hou, Min Ruan, Ruixiang Xia, Qingshu Zeng

Background: Complement activation is critically involved in multiple autoimmune diseases. Immune thrombocytopenia (ITP) is a hemorrhagic condition with enhanced platelet clearance caused by antiplatelet autoantibodies. However, the roles of complements C3a, C5a, and soluble C5b-9 (sC5b-9) in the hemorrhage of ITP remain unknown.
Methods: Plasma C3a, C5a, and sC5b-9 levels in ITP patients were measured by enzyme-linked immunosorbent assay (ELISA). Antiplatelet autoantibodies (anti-GPIIb/IIIa and anti-GPIbα) were evaluated by modified monoclonal antibody immobilization of platelet antigen (MAIPA) assay. The severity of bleeding was assessed using the validated bleeding score for each ITP patient at onset.
Results: Levels of C3a, C5a, and sC5b-9 were significantly increased in active ITP patients, compared with those in controls (p < 0.001). However, levels of C3a, C5a, and sC5b-9 were not changed by treatment of HD-DXM. In addition, the C3a levels were correlated with the increase in bleeding scores from the patients with ITP (p < 0.05, r = 0.256). In contrast, neither platelet counts nor antiplatelet autoantibodies (anti-GPIIb/IIIa and anti-GPIbα) showed any correlation with levels of C3a, C5a, and sC5b-9.
Conclusions: Levels of C3a, C5a, and sC5b-9 are increased in patients with ITP, suggesting a hyperactive complement system. Certain complement components, such as C3a, may contribute to hemorrhage of patients with ITP.

DOI: 10.7754/Clin.Lab.2016.161012