The interaction between intestinal commensal microbiota and host immune system in health and dysbiosis.

Although mucosal surfaces of the human body are colonized with innumerable microorganisms, immunological tolerance towards commensal bacteria dominates in these environments. Bidirectional communication between intestinal commensal microbiota and host immune system is essential for continuing the mutualistic partnership and intestinal homeostasis. Therefore, absence of these microorganisms or perturbations in the commensal microbiota composition, called dysbiosis, could have profound deleterious effects for the host. Here, the effect of commensal microbiota on host immune response is discussed. The enteric flora modulates immune establishment as well as function of individual immune cell types, thereby preventing pathological conditions. Identification of microbiota-derived factors that modulate host immunity would be useful for developing new therapies for dysbiosis-associated diseases