KKO-PF4/heparin IC-induced neutrophil degranulation is mediated by FcγRII and complement. Whole blood was incubated with buffer, IgG2b isotype control, or KKO (25 µg/mL) along with PF4 (25 µg/mL) and heparin (H; 1 U/mL). Or whole blood was pre-incubated for 30 minutes with IV.3 (10 µg/mL) or CP40 (25 µM) alone or in combination, or with control peptide (25 µM) before the addition of KKO-PF4/heparin. After 30 minutes, release of MMP-9 was measured in plasma. Results are expressed as mean ± standard deviation values for triplicate wells. Data shown are representative of 3 independent experiments performed in whole blood from 3 healthy donors.