Microarray data from human ILC transitional populations

Innate lymphoid cells (ILCs) are tissue-resident lymphocytes subdivided into ILC1s, ILC2s and ILC3s based on core regulatory programs and signature cytokines secreted. ILCs exhibit functional plasticity: for instance, human IL-22-producing ILC3s convert into IFN-γ-producing ILC1-like in vitro. Whether this conversion occurs in vivo is unclear. Using flow cytometry, mass cytometry and scRNAseq, here we found that ILC3s and ILC1s occupy opposite ends of a spectrum including discrete subsets in human tonsils. RNA velocity suggested strong directionality toward ILC1s for one ILC3-ILC1 intermediate cluster. Clonal analysis revealed graded ability of ILC3-ILC1 subsets to convert into ILC1-like cells. When examined in humanized mice, ILC3 acquisition of ILC1 features showed tissue-dependency. In chromatin studies, Aiolos emerged as a nuclear factor that cooperates with Tbet to repress evolutionarily conserved regulatory elements active in ILC3s. The human intestine also exhibited an ILC3–ILC1 transitional population. We conclude that conversion of ILC3s to ILC1-like occurs in vivo in human tissues, and that tissue factors and Aiolos are crucial for this process. ILCs were sorted from human tonsils. 3-4 biological replicates were analyzed per cell type.