Loss and recovery of ILCs after AML induction chemotherapy and allogeneic HSCT. (A) Gating strategy for the identification of peripheral blood ILCs, here shown for a healthy individual. ILCs are Lin⁻ (CD1a⁻CD11c⁻CD14⁻CD19⁻CD34⁻CD123⁻TCRαβ⁻TCRγδ⁻ BDCA2⁻FcεR1⁻CD94⁻), CD3⁻ lymphocytes that are CD127⁺. Groups 1, 2, and 3 ILCs are identified by the expression of CRTH2, CD117, and NKp44. Numbers in quadrants indicate the percent cells in each throughout. (B) Representative dot plot of a peripheral blood sample obtained from a patient with AML, 18 days after the first-induction chemotherapy cycle. (C) Loss and recovery dynamics of total ILCs (Lin⁻CD127⁺) during 2 AML induction chemotherapy cycles (left panel, n = 11 [cohort 1, Table 1]) and after reduced-intensity conditioning allogeneic HSCT (right panel, n = 6 [cohort 1, Table 1]). Samples were taken during neutropenia (at day 21 of each induction chemotherapy cycle), during the recovery phases of the first and second induction chemotherapy cycles, and at the days of resubmission for the second (“cycle 2”) and third (“cycle 3”; good-risk AML patients only) induction chemotherapy cycles. Patients with intermediate or poor-risk AML proceeded to allogeneic HSCT after the second induction chemotherapy cycle, and samples were collected from these patients at the day of admission to receive pre-allogeneic HSCT conditioning therapy (“allo-HSCT”). Arrows with “cycle 1,” “cycle 2,” or “cycle 3/allo-HSCT” (left panel) indicate the first day of induction chemotherapy cycles or the first day of conditioning therapy preceding allogeneic HSCT; peripheral blood neutrophil numbers had completely recovered at these time points. Dashed lines represent the 95% confidence interval (CI) as measured for healthy, age-matched controls (n = 10). (D) The recovery dynamics of total ILC (Lin⁻CD127⁺), ILC1, ILC2, NCR⁻ ILC3, and NCR⁺ ILC3 after induction chemotherapy (white bars) and 12 weeks after allogeneic HSCT (gray bars, n = 40 [cohort 2, Table 1]). Data in (C) and (D) are depicted as median values with interquartile ranges. *P < .05, **P < .01, ***P < .001. HC, healthy controls (black bars, n = 8).