The gut microbiome has emerged as a principal factor in the development and function of the immune system, and published research has linked changes in the gut microbiota to IBD risk and disease severity.20 Probiotic treatment promotes CLDN3 expression to promote gut barrier integrity.19 Therefore, we examined whether gut microbiome in Cldn3KO mice was responsible for their susceptibility to colitis. The gene discussed is CLDN3; the disease is colitis.