Recognition of the human antibody-mediated platelet destruction in adult ITP patients by C-reactive protein.

Immune thrombocytopenia purpura (ITP) is characterized by destruction of circulating platelets and the presence of antiplatelet IgG antibodies, which opsonize platelets for splenic clearance resulting in low levels of circulating platelets, and the disease severity can be predicted neither by antibody isotype nor by titer, indicating that other factors also play a role. Although the main cause of ITP remains unclear, but its relationship with some infection was demonstrated, including viral or bacterial infections. C-reactive protein (CRP), a member of the pentraxin family, is a major acute-phase protein in humans and is a clinical marker of infection. We aimed to investigate the correlation between the levels of CRP and the presence of antiplatelet IgG antibodies in adults with newly diagnosed ITP. CRP levels and platelet counts were measured in the blood samples from a 60 ITP patient (with confirmed anti-GPIIb/IIIa antibodies), 60 infection patients (all without anti-GPIIb/IIIa antibodies) and 60 normal individuals. The bleeding score, recover time of intravenous immune globulin (IVIg) therapy and the number of megakaryocytes in bone marrow were recorded in ITP patients. The platelet count, bleeding score, recover time of intravenous immune globulin (IVIG) therapy and the number of megakaryocytes in bone marrow and CRP concentrations were compared in ITP group using Spearman's correlation coefficient. We examined the influence of intraperioneal CRP administration on antibody-mediated platelet destruction in mice. There were no statistical differences in gender, age and body mass index among the three groups (P>0.05). Though CRP levels are significantly elevated in ITP patients and infection patients (P<0.05), the platelet count was markedly lower only in ITP patients. We found that CRP was inert toward platelets without antiplatelet antibodies in this study. There are a significant correlation between CRP levels and platelet counts, bleeding severity and the number of megakaryocytes in bone marrow aspiration (r=-0.5079, r=0.5498, r=0.4172, P<0.001, respectively). Moreover, a significant correlation was observed between the recovery time of platelet count and CRP levels (r=-0.5569, P<0.001). In mice, platelet count was lower in Anti-CD41 (0.75 μg)+, CRP (200 μg) group as compared with Anti-CD41 (0.75 μg)+, CRP(-) group and Anti-CD41 (0.75 μg)-, CRP (200 μg) group (P<0.05). In summary, this study indicated that CRP levels are significantly elevated in ITP patients all with confirmed anti-GPIIb/IIIa antibodies, which is able to predict the clinical bleeding severity of ITP patients. The slower CRP levels reduction after IVIg treatment predicted slower platelet count recovery in ITP.