ILC22 generation is dependent on IL-7 and SCF, but not IL-15. (A) CD34⁺ cells were cultured in varying combinations of cytokines as listed. At day 28, very few CD56⁺ cells were present in cultures lacking IL-15. At later time points, CD56⁺ cells were generated (day 35 and day 42). Representative data from a single donor is shown. (B) The CD56⁺ cells that developed in the absence of IL-15 had a phenotype of ILC22 cells (CD56⁺CD117^high CD94/7/LFA-1⁻) and expressed NKp44, CD161, IL-1R (CD121), CD25, and CXCR5. (C) These cells also showed cytokine expression (IL-22, IL-8, and GM-CSF) in response to IL-1β+23. Data are on CD56⁺ gated cells and gray-filled histograms are mouse immunoglobulin G controls. (D) The number of ILC22 cells at day 42 in the various cytokine conditions (n = 5). d, day; FL, FLT3L.