Representative effect of a combination of IL-21, IL-4, and anti-CD40 stimulation on the spontaneous apoptosis of peripheral blood CD19⁺ purified B cells from patients with CVID or IgAD. After exclusion of dead cells, equal numbers of gated B cells were assayed for annexin V staining cells at days 1, 3, and 5 either without stimulation during culture or after stimulation with IL-21 (10 ng/mL), IL-4 (0.5 ng/mL), and anti–human CD40 mAb (2 μg/mL). Annexin V expression is presented on a 4-decade log scale as histogram plots with a linear scale of the number of events at the y-axis.