Interplay between BMP4 and IL-15 in NK cell differentiation. (A) BMPRIA expression on NK cells generated after culturing CD34⁺CD1a⁻BMPRIA⁻ cells for 7 days in the presence of SCF and different doses of IL-15. (B) The levels of BMP4 were determined in the supernatants of those cultures after 3, 5, and 7 days. Results are the mean ± SD of 2 independent experiments. (C) Dot plots show forward scatter (FSC) and side scatter (SSC) properties and CD161 and CD56 expression on cells derived from cultures supplemented with SCF alone (100 ng/mL), SCF + BMP4, or SCF + IL-15 (100 ng/mL) for 6 days. (D) Expression of CD122 and CD215 on thymic precursors after treatment with SCF and BMP4 for 36 hours. Control cells were cultured with SCF + IL-15. The percentages of positive cells (and their mean fluorescence intensities) are indicated in the histograms. One representative experiment of 3 is shown. (E) Expression of NK cell differentiation related genes after BMP4 or dorsomorphin treatment. Thymic CD34⁺CD1a⁻BMPRIA⁻ precursors were cultured for 36 hours with SCF + IL-15 and then pulsed for 1 hour with BMP4. To inhibit endogenous BMP signaling, dorsomorphin was present during the whole culture period. Transcription levels of different genes in BMP4- or dorsomorphin-treated precursors were normalized for GNB2L1 mRNA content and are shown relative to GNB2L1-normalized transcription in the untreated cells. Data represent the mean ± SD from 2 to 3 independent experiments.