IdeS-IV.3–treated platelets have increased survival in murine models of ITP. (A) Mouse platelets expressing FcγRIIA were treated in vitro with scIV.3 or scIV.3-IdeS and then incubated with increasing concentrations of RAMS, and full-length platelet-bound IgG was measured (n = 3). (B) Mice expressing human Fc receptors were treated with control or IV.3-IdeS (10 μg) and then injected with 10 or 20 μg of RAMS. Platelet counts were performed 24 hours after RAMS injection and were normalized to pre-IgG injection (pre) measurements. (C) The amount of surface-bound His-tagged scIV.3-IdeS on mouse platelets was quantified by flow cytometry 0.5, 2, and 24 hours after IV.3-IdeS treatment. CFSE-labeled mouse platelets expressing FcγRIIA were treated with scIV.3-IdeS or control and transfused into mice that were injected with RAMS 24 hours before transfusion. (D-E) The total and transfused platelet counts were measured using a Cytek Aurora flow cytometer at 1 (D) and 4 hours (E) posttransfusion (data represent mean ± standard deviation; 1-way analysis of variance). *P < .05, **P < .01, ***P < .001. MFI, median fluorescence intensity.