BAFF and APRIL stimulate NF-κ B activation in B-CLL cells. Leukemic B cells were incubated for various times with the indicated concentrations of BAFF or APRIL. Extracts were then estimated for the activation of NF-κ B using an ELISA test (TransAm NF-κB) with a specific anti-p65 antibody. (A) BAFF and APRIL dose response after 4 hours of treatment. (B) Time response. (C) Specificity of the binding (16 hours). (D) Reversal of BAFF and APRIL protective effect on spontaneous apoptosis (measured by cytoplasm nucleosome enrichment) by adding 10 μM DETC, an inhibitor of NF-κB activation. Results are expressed as cytoplasm nucleosome enrichment in comparison with untreated cells taken as 1.