Pretreatment of platelets with chondroitinase ABC inhibits HIT serum-induced platelet aggregation. Platelets, 800 × 10⁹/L, were preincubated with 0 (A), 0.2 (B), 0.5 (C), and 1 (D) μ/mL chondroitinase ABC at 37°C for 30 minutes before stimulation with HIT sera. Agonists were added at time points indicated by arrows. A total of 10 μg/mL PF4 and 0.5 U/mL heparin was added 1 minute before adding HIT sera as agonists. The aggregation curves are representative of the results from three experiments with HIT sera 1, 3, and 4 and platelets from three different donors.