Identification of a CD56⁺ILC1-like population with NK properties that is impaired in AML patients at diagnosis. (A-B) Representative density plots of the extracellular flow cytometry panel used to identify the cNK cell subsets (A) and the ILC subsets (B) in peripheral blood (PB) mononuclear cells (PBMCs; ILC1 as CRTH2⁻ c-Kit⁻ CD56⁻, ILC2 as CRTH2⁺ c-Kit^+/− CD56^+/−, ILCP as CRTH2⁻ c-Kit⁺ CD56^+/−, and cNKs as CD16⁻ CD56^bright and CD16⁺ CD56^dim).^21,22  Lineage markers used for the “helper” ILC staining include CD3, CD4, CD8, CD14, CD15, CD16, CD19, CD20, CD33, CD34, CD203c, and FcεRIα; same lineage markers, except for CD16, were used for the cNK staining. (C) CD127, CD56, CD16, CRTH2, c-Kit fluorescence intensity on ILC and NK subsets were concatenated from 5 HDs and analyzed with t-distributed stochastic neighbor embedding (t-SNE). c-Kit, CD127, CD56, CD16 expression levels on ILC1, CD56⁺ ILC1-like cells and NKs are represented in panel D. Representative gating (E) and quantification of CD56⁺ ILC1-like cell and cNK proportions among lymphocytes in blood from HDs and AML patients at diagnosis (F) (CD56⁺ ILC1-like cells: HD, n = 47; AML patients: n = 60; cNKs: HD: n = 12, AML: n = 18). (G) Summary of the results of the total ILC proportions and ILC1, ILC2, ILCP, and CD56⁺ ILC1-like cell subset frequencies among the total ILCs in HD peripheral blood (N = 47, age median 48, interquartile range 31 to 64). (H) Correlation between ILC subsets’ relative frequencies in blood and age (cord blood: n = 9, children: n = 6, [3 to 12] years old, adults: n = 47, age mean 48). (I) CD56⁺ ILC1-like cell relative frequencies among the total ILCs in tissues from healthy adults (n = 3-18). Spearman correlations were used in panel H. One dot = 1 donor. Mann-Whitney unpaired U tests were used in panel F. ****P < .0001. BM, bone marrow; LN, lymph node. ns, not significant.