RA signaling is essential for intestinal adaptation of ILC2s in vivo. (A) Experimental design of the RAi (BMS493 220 µg) treatment of ILC2-transferred BALB/c Rag2^−/−Il2rg^−/− mice. Kidney ILC2s isolated from IL-33–treated BALB/c IL-13^fm mice (i.p. injections on four consecutive days) were adoptively transferred through i.v. injections into BALB/c Rag2^−/−Il2rg^−/− recipient mice (n = 11). The recipient mice received either DMSO (n = 5) or RAi (n = 6) treatment at the indicated time points. (B) Representative FACS plots of Lin⁻IL-13^fm+ ILC2s isolated from the kidneys, lungs, and SILP of BALB/c Rag2^−/−Il2rg^−/− mice after 3 wk of transfer and treatment with either DMSO or RAi. Numbers indicate the percentage of cells in each gate. (C) Frequencies and absolute numbers of IL-13^fm+ ILC2s isolated from the kidney, lung, and SILP of BALB/c Rag2^−/−Il2rg^−/− mice treated with either DMSO or RAi. (D) MFI of different surface marker expressions of ILC2s isolated from the respective organs. (E) Experimental design of the RAi treatment of BALB/c Rag2^−/− and BALB/c IL-13^fm mice. The mice received either DMSO (n = 5) or RAi (n = 7) treatment for 3 wk, and ILC2s from the kidney, lung, and SILP were analyzed. (F and G) Absolute numbers and ILC2/ILC3 ratio of Lin⁻GATA-3⁺ ILC2s, Lin⁻IL-13^fm+ ILC2s, and Lin⁻RORγt⁺ ILC3s isolated from the kidney, lung, and SILP of BALB/c Rag2^−/− (F) and BALB/c IL-13^fm (G) mice. (H and I) MFI of different surface marker expression of ILC2s isolated from the respective organs of BALB/c Rag2^−/− (H) and BALB/c IL-13^fm mice (I). Data are pooled from two individually performed experiments. Symbols represent individual data points and bars indicate mean ± SEM. Statistical analysis was performed using unpaired two-tailed Student’s t test (*P < 0.05, **P < 0.01, ***P < 0.001).