IL-7 supports BMDC survival in vitro. (A) Flow cytometric analysis of day 10 WT BMDCs (CD11c⁺ MHCII⁺) for IL-7Rα (middle panel, black line) and γ_c-chain expression (bottom panel, black line). As control, IL-7Rα staining is shown for IL-7Rα^−/− BMDC (middle panel, gray shading) or isotype-control antibody staining on WT BMDCs (bottom panel, gray shading). (B-D) Day 10 BMDCs were cultured in the absence of GM-CSF, and their survival was assessed by trypan blue dye exclusion. No significant differences were observed between MHCII^hi and MHCII^int CD11c⁺ BMDCs (data not shown) and were therefore pooled for the analysis. (B) BMDCs were cultured for 24 hours either alone (−), in the presence of increasing concentrations of recombinant IL-7 protein, on a layer of subconfluent LN stromal cells (ratio of 10 BMDCs to 1 stromal cell), or with supernatant (SN) derived from a 3-day LN stromal cell culture. (C) Neutralizing antibodies to IL-7 (10 μg/mL) or IL-7Rα (20 μg/mL) were added to BMDCs cultured for 24 hours with LN stromal cells. (D) Culture of BMDCs with or without LN stromal cells for 1, 2, or 5 days. P values (*P < .05; **P < .01; ***P < .001) are relative to the same time point of the “no-stroma” control. Data (± SD) are representative of at least 2 experiments with 3 independent samples each.