PKCβII activity regulates BCR-induced Ca²⁺ release in CLL cells. (A) CLL patients with high and low PKCβII activity (defined, respectively, as containing amounts of active PKCβII greater than or less than 1 SD from the mean value) were stimulated with 20 μg/mL anti-IgM antibody (BCR-XL), and intracellular Ca²⁺ release was measured using the dye Indo-1. Comparison of BCR-induced Ca²⁺ release in CLL patients with high and low levels of active PKCβII. Western blot analysis of ZAP-70 expression in these patients is shown in the inset. CLL21 is the CLL patient with low PKCβII activity. CLL50 is the CLL patient with high PKCβII activity. (B) Comparison of peak Ca²⁺ levels (mean ± SD) during BCR stimulation of CLL patients with high (n = 5) and low (n = 5) levels of active PKCβII. (C) One-hour pretreatment with 100 nM LY379196 restores BCR-induced Ca²⁺ release in CLL patients with high levels of active PKCβII. (D) Thirty-minute pretreatment with 10 nM bryostatin suppresses BCR-induced Ca²⁺ release in CLL patients with low levels of active PKCβII. (C-D) Representative examples of 3 separate experiments using cells from different patients.