We also showed that glutamine affects the intestinal immune system, such as the activation of toll-like receptor (TLR)-4-nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), phosphoinositide-3-kinases (PI3K)/PI3K-protein kinase B (Akt) signaling, the expression of inflammatory cytokines [e.g. interleukin (IL)-17], and the production of secretory immunoglobulin A (SIgA), leading to alteration in intestinal microbiota and inhibition of intestinal infection (18, 19, 25, 37, 38). The gene discussed is TLR4; the disease is digestive system infectious disorder.