Bacterial colonization, probiotics, and clinical disease

With the emergence of the hygiene hypothesis, science has begun to reconsider the role of bacteria in host health. Data from germ-free animals and clinical studies support the idea that the colonization of intestinal flora and bacteria-host cross-talk play pivotal roles in the development of the mucosal immune system. Here we discuss the role of commensal colonizing bacteria and toll-like receptor/nucleotide-binding oligomerization domain (TLR/NOD) receptors in the regulation of intestinal immunity and the relationship between TLR/NOD and immune-mediated disease, especially inflammatory bowel disease. We also explore the mechanism of the induction of immune hyporesposiveness by gut epithelial cells interacting with commensal bacteria. A better understanding of bacteria-host interactions will help provide a rational basis for using probiotics as a dietary supplement to prevent and treat disease in the future.

Abbreviations: CAMP, Commensal-associated molecular pattern, CARD, Caspase-activating recruitment domain, CD, Crohn’s disease, DC, Dendritic cell, IBD, Inflammatory bowel disease, IEC, Intestinal epithelial cell, IL, Interleukin, LPS, Lipopolysaccharide, NOD, Nucleotide-binding oligomerization domain, PAMP, Pathogen-associated molecular pattern, Th1, Type 1 helper cell, Th2, Type 2 helper cell, TLR, Toll-like receptor, TNF, Tumor necrosis factor, Treg, Regulator T-cell