IL-21 induces apoptosis in DLBCL primary tumors. Neoplastic or healthy B cells isolated from primary de novo tumors or normal tonsils were treated with IL-21 (100 ng/mL) for the specified time period and viability was assayed using YO-PRO/PI staining. (A) Flow cytometric profiles of B cells isolated from one representative DLBCL primary tumor originating from patient 4 and stained with YO-PRO/PI. (B) Compilation of viability data for B cells isolated from 5 DLBCL primary tumors and 1 healthy tonsil tested by flow cytometry after 72 hours of IL-21 treatment. (C) Flow cytometric profiles of healthy B cells isolated from a representative normal tonsil (tonsil 1) and stained with YO-PRO/PI. (D) Compilation of viability data for B cells isolated from 7 chronic lymphocytic leukemia (CLL), 3 follicular lymphoma (FL), and 1 marginal zone lymphoma (MZL) patient samples tested by flow cytometry after 72 hours of IL-21 treatment.