Abstract
OBJECTIVE: To investigate the role of the IgG subtypes（IgG1 and IgG2a）in anti-glycoprotein（GP）Ⅰbα antibody-induced platelet clearance. METHODS: Venous blood was collected from healthy volunteers, and platelets were separated. The phagocytosis of human platelets by human acute monocytic leukemia cells（THP-1 cells）induced by different anti-GPⅠbα antibodies（AN51, AK2, HIP1, TM60, VM16d, WM23, and SZ2）was detected by flow cytometry. The effects of the AN51 full-length antibody, F（ab'）(2), and Fab fragments on platelet phagocytosis by THP-1 cells were detected by flow cytometry. Then, the Fc blocking antibody 2.4G2 and normal rat IgG2a or IgG1 were injected into C57BL/6J mice via the posterior ocular vein, and their effects on platelet reduction induced by R300 were detected by a hematology analyzer. RESULTS: Compared with IgG1, the IgG2a subtype of anti-GPⅠbα antibodies induced the phagocytosis of platelets by THP-1 cells in vitro（P<0.05）. In contrast to the AN51 full-length antibody, neither AN51 F（ab'）(2) nor the Fab fragment could induce THP-1 cells to phagocytose platelets（P<0.05）. Compared with the control group, anti-mouse GPⅠbα R300-induced thrombocytopenia in mice was reduced at 2, 4, and 6 h after the injection of Fc blocking antibody 2.4G2（P<0.05）. Similarly, R300-induced thrombocytopenia in mice was reduced at 2, 4, and 6 h after the injection of rat IgG2a（P<0.05）. CONCLUSION: IgG2a plays an important role in anti-GPⅠbα-induced clearance.