IL-21 induces de novo granzyme B synthesis and secretion by benign peripheral B cells and different B-cell lines. Standard cell lines, EBV transformed lymphoblasts, and B cells from healthy subjects (> 99.5% CD19⁺) were cultured in medium alone, anti-BCR, CpG ODN, IL-21, or combinations of these agents for 16 hours at a concentration of 100 000 cells/well. ELISPOT analysis for granzyme B was then performed. Controls included isolated B cells and unfractionated PBMCs treated with PHA.