In contrast to wild‐type mice, the compositions of microbiotas in Il10−/− mice are also changed.[24] In agreement with the notion that Il10−/− mice would not develop colitis until 2 months,[15a] we observed evident rectal prolapse in 8‐week‐old Il10−/− mice but not in 4‐week‐old ones (Figure S9c, Supporting Information). This evidence concerns the gene IL10 and colitis.