Antibiotics ameliorate spontaneous colitis in cKO mice. (A and B) Representative images of spleens and mLNs (A) and spleen weight (B) of WT and littermate control cKO mice treated or not treated with antibiotics. (C and D) Representative images of colons (C) and colon length (D) of WT and littermate control cKO mice treated or not treated with antibiotics. (E) H&E staining of ileum and colon of WT and littermate control cKO mice treated or not treated with antibiotics. Scale bar, 100 µm. (F and G) Quantification of a histological score of the ileums (F) and colons (G) of mice as in E. (H) Representative flow plots of proliferating Ki-67⁺ and activated CD44⁺ CD4⁺ T cells from SI of WT and littermate control cKO mice treated or not treated with antibiotics. (I and J) Quantification of the frequency of proliferating Ki-67⁺ (I) and activated CD44⁺ (J) CD4⁺ T cells as in (H). (K) Representative flow plot of T-bet⁺ ILC3s (upper panel) and IFN-γ production by ILC3s after stimulation with PMA plus ionomycin ex vivo. ILC3s were isolated from SI of WT and littermate control cKO mice treated or not treated with antibiotics. FSW, forward side pulse width. (L and M) Quantification of the frequency of T-bet⁺ (L) and IFN-γ⁺ (M) SI ILC3s as in K. Antibiotics (Abx) were continuously administered in the drinking water of WT and littermate control cKO mice at weaning until 11–13 wk of age. Data shown as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 (two-tailed unpaired t test). Each dot represents one mouse, n = 3–8 mice per group. Data are pooled from two independent experiments.