Interleukin 21 (IL-21) induces de-novo synthesis of Granzyme B by activated B cells.Peripheral blood mononuclear cells (PBMC) were stimulated with the above depicted agents for 18 hours. After further incubtion with Brefeldin A for 4 hours cells were harvested, fixed, permeabilized, stained with PE- and PE-Cy5-labeled antibodies against Granzyme B and CD19, and analyzed flowcytometrically.