Components of<unk>  immune system<unk>  is the study of immune system responses that occur at<unk>  membranes of the intestines, the urogenital tract, and the respiratory system. The mucous membranes are in constant contact with a large number of microorganisms, food, and inhaled air antigens. In healthy states, the<unk>  immune system protects the organism against infectious pathogens but also maintains a tolerance towards non-harmful commensal microbes and benign environmental substances. Disruption of this balance between tolerance and deprivation of pathogens can lead to various pathological conditions such as food allergies, irritable bowel syndrome, susceptibility to infections, and more. The<unk>  immune system consists of a cellular component, humoral immunity, and defense mechanisms that prevent the invasion of microorganisms and harmful foreign substances into the body. These defense mechanisms can be divided into physical barriers (epithelial lining, mucus, cilia function, intestinal peristalsis, etc.) and chemical factors (pH, antimicrobial peptides, etc.).
Mucosal immunology
Gastrointestinal physiology
Immunology
Sensation 
Immune system
Cancer immunology
Cognition
Biochemistry