I have a master degree in Molecular biology followed by a PhD in Immunology from Gothenburg University in Sweden. My thesis projects involved investigations on a subset of regulatory cells that are important for your innate immunity but also important for the link between the innate and adaptive immunity. Simplified, your Innate immunity is the immunity you´re born with and the adaptive immunity is the immunity your body creates though experience. The adaptive immunity is where your body creates it´s memory. For example when you are injected with a vaccine, there are structures that comes from microbes/looks like microbes that your body recognizes as danger and therefore creates an immune response. Your innate immunity “wakes up” and senses that something foreign has intruded – It starts an immune response and connects to the adaptive immunity which in term creates a memory. Next time when the real microbe comes along your adaptive immunity already has a memory against the microbe, it is prepared and can fight off the intruder more efficiently. This is also why you sometimes can get sick from a vaccine, since you actually create an immune response, although a minor one.
How come food doesn’t create an immune response? Or does it? It´s very fascinating that your body normally tolerates tons of different foods without initiating an immune response. How does the immune system discriminates between harmful pathogens and harmless antigens? The mechanism of action is tolerance or oral tolerance. Failure to induce tolerance to food proteins may result in food allergy and celiac disease. Further, the intestines are packed with commensal microbes or microbiota that covers the epithelial lining in the intestines and colon. If your immune system starts to attack the microbiota you can develop inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis. During the development of immune cells they undergo several tests to make sure they are functional and are tolerant to self substances – this is called selection. Some cells actually get to see a repertoire of self-antigens before they are released systemically. If they respond to these self-antigens they are eliminated. In addition to teaching the cells what to react to or not react to, your immune system also have regulatory cells. These cells are cells that helps in terms of regulating the immune response. They usually act rapidly and can direct other immune cells. As you can imagine, your immune system is a very dynamic and complex system and failure in oral tolerance is quit common.