KKO/HIT ULICS activate complement and lead to deposition of complement on neutrophils, monocytes, and B cells. Main figures show binding (mean fluorescence intensity [MFI]) of α-C3c (top) or α-mouse IgG (bottom) to defined cell populations after incubating WB with conditions indicated on the x-axis and analyzed by flow cytometry. Cell populations were gated by labeled Abs to CD66 (neutrophils), CD14 (monocytes), and CD19 (B cells). Insets for each graph show respective cell population when WB was incubated with buffer (B) or HIT IgG (HIT) alone or with PF4/heparin (P+H+HIT) or ISO/control with PF4/heparin (P+H+ISO). The graphic is representative of ≥3 independent experiments using KKO and complement-activating HIT IgG. **P < .005, ***P < .0001 (compared with all other conditions using 1-way analysis of variance with Tukey’s multiple comparison test).