Stimulation of CLL cells with CD154 can induce expression miR-155, downregulation of SHIP1, and enhanced BCR signaling. (A) Expression of miR-155 in CLL cells without (−) or with (+) CD154 stimulation. The height of each column in the histogram corresponds to the fold increase in expression of miR-155 in CLL cells stimulated with CD154 (+) relative to that in CLL cells that had not been so stimulated (−), as indicated at the bottom of the histogram. We determined statistical significance using the paired Student t test (P < .05). (B) Expression of SHIP1 in CLL cells without (−) or with (+) CD154 stimulation, as indicated at the bottom of the histogram. The height of each column corresponds to the mean MFIR for SHIP1. (C) Anti-µ–induced calcium mobilization in CLL cells without (Ct, top panel) or with (CD154, lower panel) CD154 stimulation. The relative mean fluorescence intensity in intracellular calcium is plotted as a function of time. The arrow labeled “IgM” indicates the time at which the anti-µ was added to the cells (left panel). The histogram to the right depicts the mean increase of fluorescence intensity of CLL cells following stimulation with anti-µ without (−) or with (+) prior stimulation with CD154, as indicated at the bottom of the histogram. (D) Anti-µ–induced calcium mobilization in CLL cells with (+) or without (−) CD154 stimulation after the cells were transfected with a control oligonucleotide (oligo-ct) or miR-155 inhibitor. The height of each column in the histogram corresponds to the mean increase of fluorescence intensity after treatment with anti-µ of CLL cells. We determined statistical significance using 1-way analyses of variance (P < .05).