2Mucosal immunology and bacterial handling in the intestine

The mucosal immune system has the very difficult task to protect against invaders and to promote tolerance toward food antigens and the microbiota. These activities are achieved via a complex interaction between immune cells and the local microenvironment. Under the unperturbed (steady-state) condition the immune system is set toward the activation of tolerogenic responses. During infection the immune system is prompted to initiate immunity. When these two activities are not coordinated, inflammatory conditions may arise. In this review I will summarize the characteristic features of the mucosal immune system and its interaction with the microbiota.