Induction of IgG production in PBMCs from 5 randomly chosen healthy donors presented as mean values. Units of secreted IgG were measured in a virtual unit that is equivalent to the surface in 0.01 mm² multiplied by the intensity of a particular spot in ELISPOT analysis. (A) PBMCs (10⁶) were stimulated for 5 days with either 10 or 100 ng/mL IL-4, IL-10, or IL-21 alone or in combination with 2 μg/mL anti-CD40 mAb. Subsequently, 10⁵ PBMCs were subjected to ELISPOT assay for 20 hours of incubation. (B) PBMCs (10⁶) were stimulated for 5 days with 2 μg/mL anti-CD40 mAb and 0.5 ng/mL of either IL-2, IL-4, IL-6, IL-7, IL-15, or IL-10 alone or in combination with 10 ng/mL IL-21. PBMCs (5 × 10⁴) were subjected to ELISPOT assay for 20 hours of incubation.