Macroscopic observations of colons on day 7 showed that colon shortening occurred in WT colitis mice but was significantly alleviated in IL-4Rα-/- colitis mice (Figures 2A,B; 7.5 ± 0.2 cm in WT colitis, 10.1 ± 0.5 cm in IL-4Rα-/- colitis; p < 0.001). Here, IL4R is linked to colitis.