miR-155 modulates DC apoptosis. (A-B) Forced overexpression of miR-155 induced imDCs to undergo apoptosis. imDCs at day 4 were transfected with miR-155 precursors and negative controls at the final concentration of 40nM for 24 hours. Cells were analyzed for apoptosis by staining with PI (A) or APC-annexin V (B) to detect percentage of sub-G₀ fraction and apoptosis. (C) Induction of apoptosis in mDCs after overexpression of miR-155. (D) Less apoptosis in activated DCs from miR-155^−/− mice than DCs from WT mice. Murine imDCs were generated from BM cells and purified by anti-CD11c microbeads. Purified imDCs (2.5 × 10⁵ per well) were then cultured in 24-well plates in the presence of murine GM-CSF (20 ng/mL) and stimulated with LPS (1 μg/mL). Cells were watched every day under an inverted microscope. At days 4 and 5, cells were collected and stained with APC-annexin V and PI for analysis of apoptosis. (E) Less p27^kip1 expression in activated DCs from miR-155^−/− mice than WT DCs. Activated mDCs by LPS (1 μg/mL) for 4 days were analyzed for p27^kip1 expression by Western blot. The data shown in every panel are representative of 2 (D) or 3 (A-C,E) independent experiments.