Cleavage of anti-PF4/H IgG by IdeS in WB and impact on H-dependent platelet activation and aggregation. (A,D) Western blot analysis after cleavage in whole blood by IdeS of 5B9 (A) or human HIT IgG (D) (n = 2 experiments). The amount of IdeS added varied from 0.002 to 0.02 U/μg IgG, considering that IgG concentration in whole blood from healthy donors was ∼7.5 mg/mL. (B,C-E) Representative platelet aggregation curves obtained with 5B9 (B), collagen and ADP (C), and human HIT plasma samples (E), without and with IdeS (n = 3 experiments). (F) Maximal serotonin release (mean ± SEM; n = 3 platelet donors) induced by thrombin (1 U/mL), 5B9 (20 µg/mL), or HIT plasma samples with 0.1 IU/mL UFH, previously treated or not with IdeS (0.02 U/µg IgG; 6 minutes at 37°C). All experiments were performed with whole blood from 2 or 3 healthy donors. *P < .05. AU, arbitrary units.