In vivo efficacy of 2.4G2 scFv-MSA in ITP amelioration. (A) Mice were pretreated intravenously with 10, 20, 40, or 80 µg of 2.4G2 scFv-MSA or 56 µg HSA (equimolar amount as 80 µg 2.4G2 scFv-MSA) for 2 hours before ITP induction by administration of 2 µg antiplatelet antibody MWReg30. Mice were then bled after 2, 24, and 48 hours, and platelets were enumerated using a Z2 particle counter. ***P < .01 compared with HSA at each time point; n = 6–8, from 4 independent experiments. (B) Mice were pretreated with 25 mg IVIg (intraperitoneally), 80 µg 2.4G2 scFv-MSA, or 56 µg HSA for 2 hours before ITP induction by administration of 3 µg antiplatelet antibody 6A6. Mice were then bled after 2, 24, and 48 hours and platelets were enumerated using a Z2 particle counter. n = 6–7, from 4 independent experiments.