Omalizumab did not induce apoptosis in human B cells. B cells were left non-treated (NT) or treated with IL-4 + anti-CD40 in the presence or absence of 1 μg/mL omalizumab (Om) or human IgG. After 3 days B cells were stained with 7-AAD and PE-conjugated Annexin V and analyzed by flow cytometry. Panels A – C: Representative experiment of 4 independent experiments. Percentage of Annexin V positive cells is indicated in the lower right quadrant. (A) IL-4 + anti-CD40 (B) IL-4 + anti-CD40 + Om (C) IL-4 + anti-CD40 + IgG. Panel D: Mean percentage of Annexin V+ cells ± SEM from 4 separate independent experiments (4 tonsils).