We further compared the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive apoptosis cells in colon sections of conventionally housed WT and IL-37tg colitis mice by day nine and found increased numbers of TUNEL-positive epithelial cells in IL-37tg colitis mice (Figure 2B), suggesting that IL-37 impairs epithelial tight junction integrity in conventionally housed colitis mice. Here, IL37 is linked to colitis.