Figure 1.

The mucosal immune system constitutes a key element in preventing penetration of microorganisms. It consists of innate and adaptive immune responses. The innate immune response is the first line of defense against infection and includes complement proteins, granulocytes (basophils, eosinophils and neutrophils), mast cells, macrophages, dendritic cells and natural killer cells. The adaptive immune response develops more slowly, but it is manifested as increased antigenic specificity and memory. It consists of antibodies, B cells, and CD4⁺ and CD8⁺ T lymphocytes. Disruption of the innate and acquired gut immune systems may cause the development of chronic intestinal diseases.