Protective effects of IVIG against platelet clearance mediated by QITP and ITP antibodies. (A) Mice were injected with IVIG (1 g/kg) after administration of QITP sera and quinine. In addition, control mice were injected with PBS buffer instead of IVIG but they still received QITP sera and quinine or QITP patient sera alone. Mean survival curves are shown for each group. (B) Bar diagram showing MPLs of the 3 groups of mice described in panel A. The MPLs of human platelets in mice treated with patient sera, quinine and IVIG () were significantly increased (P = .006) compared with MPLS in mice treated with patient serum and quinine and no IVIG (▬) but did not reach the MPL values in control mice treated with patient sera, no quinine and no IVIG (▭). (C) Mean survival curves of human platelets in mice injected with IVIG (1 g/kg) after administration of ITP sera are shown in comparison with the survival curves of control mice injected with ITP sera or normal AB sera plus PBS buffer (no IVIG). (D) Bar diagram showing MPLs of the 3 groups of mice described in panel C: the MPLs of human platelets in mice treated with ITP patient sera and IVIG () were significantly increased (P = .016) compared with the MPLs of human platelets in mice treated with ITP patient serum but no IVIG (▬) but MPLs were not restored to the levels observed in control mice treated with normal AB sera but no IVIG (▭). MPLs in mice treated with IVIG and mice not treated with IVIG were compared using the Mann-Whitney U test. Results were considered statistically significant when P < .05. (E) Survival curves of human platelets in mice treated with different doses of IVIG (1 g/kg, 0.5 g/kg, 0.25 g/kg, and 0 g/kg) were compared. (F) Dose-dependent increase in MPLs was observed with increasing doses of IVIG, suggesting the IVIG protective effect is dose-dependent.