Expression of IL-15 and IL-15Rα in CD11c-IL-15Rα Tg mice. (A) Histograms show IL-15Rα expression on myeloid subsets in Wt, CD11c-IL-15Rα Tg-1 and Tg-2, and IL-15Rα^−/− mice after gating on lineage-negative (CD3, CD19, DX5) splenocytes. Filled histograms indicate IL-15Rα staining on indicated populations, open histograms represent staining of the same population from IL-15Rα^−/− mice. (B) Histograms show IL-15Rα staining on the respective lymphoid populations: top 3 panels are CD4⁺TCRαβ⁺, CD8⁺TCRαβ⁺, NK1.1⁺-TCRαβ⁻ cells from the spleen; bottom 3 panels show respective IEL populations. (C,D) Splenocytes (10⁷) from Wt, CD11c/IL-15Rα Tg-1, Tg-2, and IL-15^−/− mice were cultured overnight in CM prior to staining. Filled histogram indicates IL-15 staining, the open histogram represents staining of the same cells from IL-15^−/− mice. Histograms in panel C were first gated on lineage-negative cells as in panel A. (E) Splenocytes were treated as in panel C, in the absence or presence of 1 μg/mL LPS. IL-15 staining was determined after gating on CD11c^hi CD11b⁺ cells.