Autocrine TGF-β1 is essential for t r NK cells in glandular tissues. (A) Expression of Tgfb1 in group 1 ILCs from indicated tissues in publicly available scRNA-seq datasets (Sparano et al., 2022; Yomogida et al., 2021; Kimmel et al., 2019). (B and C) Representative flow cytometry plots and quantification of LAP on splenic NK cells from (B) Tgfb1^fl (WT) and Ncr1^CreTgfb1^fl mice or (C) WT CD27⁺ and CD11b⁺ subsets before and after stimulation with PMA and Ionomycin (PMA/Iono), IL-12 and IL-18, or IL-15 for 12 h. (D) LAP expression on human peripheral blood CD56^Dim and CD56^Bright NK cells, before or after 48 h stimulation with IL-2 (100 U/ml). (E) Flow cytometric quantification of group 1 ILC (Lin⁻ NK1.1⁺NKp46⁺) percentage among live CD45⁺ cells in indicated tissues. SI, small intestine. (F–H) Representative flow cytometry plots and quantification of group 1 ILC subsets in (F) salivary glands, (G and H) uterus, pancreas, and choroid plexus (CP). (I) Experimental scheme for J. Ncr1^CreERT2 and Ncr1^CreERT2Tgfb1^fl mice were treated three times with tamoxifen via oral gavage (o.g.) and analyzed 7 days later. (J) Flow cytometric quantification of SG group 1 ILC subsets. (K) Experimental scheme for L and M. BM from indicated mice was mixed at 50:50 rate and injected intravenously into lethally irradiated CD45.1.2 hosts. Hosts were analyzed 6 wk after reconstitution. (L and M) Normalized ratio of WT and Ncr1^CreTgfb1^fl contribution to indicated subsets (L) and representative flow cytometry plots (M) of SG group 1 ILCs. (B and C) Data are representative for one of two to three independent experiments with n = 4–6 mice per group or (D–M) pooled from two to three independent experiments with total n = 5–10 per group. Error bars display means ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) or two-tailed t test; *P < 0.05, **P < 0.01, and ****P < 0.0001. ns, not significant.