Anti–IL-2Rβ or anti–IL-2Rγ antibodies inhibit the mitogenic activity and antiapoptotic effect of IL-15. (A) CD40-activated CLL cells (case no. 1) were cultured in triplicate wells of 96-well plates in the presence of IL-15 (50 ng/mL) with or without anti–IL-2Rβ or anti–IL-2Rγ antibodies or with an irrelevant antibody (anti-CD25) for 48 hours and then pulsed with 3H-thymidine for additional 18 hours. Error bars represent SD. (B) CLL cells from a representative patient (no. 12) were cultured for 4 days in the presence or absence of anti-IgM antiserum, IL-15 (50 ng/mL), and anti–IL-2Rβ or anti–IL-2Rγ antibody (5 μg/mL), as indicated. Apoptosis was evaluated by 2-color fluorescence analysis of propidium iodide (PI) and annexin-V staining. (C) CD40-activated CLL cells (no. 12) were cultured in the presence or absence of IL-21 (50 ng/mL) and anti–IL-2Rβ or anti–IL-2Rγ antibody (5 μg/mL), as indicated and apoptosis was evaluated as described in panel B. The numbers on the plots are the percentages of total cells in the respective quadrants.
