miR-155 levels in normal B cells, MBL cells, and CLL cells as measured by qRT-PCR. (A) miRNA expression in isolated and purified B cells from the training set (group A). (B) miRNA expression in isolated and purified B cells from the validation set (group B). Comparisons between MBL and Rai 0 for each set of samples are presented in panels C-D. We used 5S rRNA as a normalizer. Raw data for all samples are shown in supplemental Table 3. In panels A-B, the P values were calculated using the Kruskal-Wallis test.