miR-217 expression is upregulated in activated B cells. (A) qRT-PCR analysis of the expression of the (left) miR-217 precursor and (right) mature miR-217 in B cells after 1 (open bars) and 3 days (filled bars) of activation with LPS + IL4. Data from 3 (miR-217 precursor) and 2 (mature miR-217) independent experiments are shown (P = .05 for miR-217 precursor and P = .27 for miR-217). Each experiment was performed with 2 individual mice. (B) qRT-PCR of the (left) miR-217 precursor and (right) mature miR-217 in resting (open bars) or GC (filled bars) B cells isolated from spleens of wild-type C57BL/6 mice 10 days after immunization with sheep red blood cells. Data are means ± standard deviation from 2 independent experiments with 10 total immunized mice (P = .0002 for miR-217 precursor and P = .01 for miR-217). Two-tailed Student t test: P values: *P < .05. (C) Quantification of miR-217 expression in human resting (CD19⁺CD27⁻IgD⁻) and GC (CD19⁺CD10⁺) samples as measured by miRNA array hybridization (data were obtained from GSE29493, P = .003, 2-tailed Student t test). (D) Representative fluorescence-activated cell sorter (FACS) analysis of bone marrow from miR-217^TG, miR-217^KI and littermate control mice. Plots show the expression of (left) B220/CD19 in total live lymphocytes, (center) IgD/IgM gated in B220⁺CD19⁺ cells, and (right) CD25/B220 gated in B220⁺CD19⁺IgM⁻IgD⁻ cells. The proportion of cells is indicated in each gated in B220⁺ cells. (E) Quantification of the proportions and absolute cell numbers of developing bone marrow B-cell subsets in control (open bars), (upper) miR-217^TG (filled bars), and (lower) miR-217^KI mice (filled bars). The proportions of different B-cell subsets were quantified within the B220⁺ population.