Stage 4A NKDIs are bipotent precursors to ILC3s and NKp80+ NK cells. (A) Clonal analyses of freshly purified tonsil-derived stage 4A and stage 4B cells individually sorted into wells containing OP9-DL1 cells supplemented with IL-7 and IL-15 (10 ng/ml) for 21 days. Clones were analyzed for stage 3/ILC3-like (CD94−NKp44+), stage 4A-like (CD94+NKp80−), and stage 4B-like (CD94+NKp80+) cells. (107 total clones evaluated from n = 6 donors; 3 independent experiments). Cloning efficiency was approximately 10% for stage 4A clones and 25% for stage 4B clones. (B-C) Representative (n = 3; 1 independent experiment) flow cytometry analyses depicting stage 4A-like (CD94+NKp80−, left panels, red boxes) cells that were sorted at in vitro culture day 14 and re-plated with IL-7 and Fc control, recombinant human Delta-like-1 (immobilized on plate at 4 μg/ml), or OP9-DL1 cells.