Question

Question 7: The microbiome contains an ecosystem of microorganisms/foreign antigens. Why doesn’t the body attack the gut?

Answer 1

The immune system exhibits self-nonself tolerance. Self-antigens are presented to lymphocytes during their maturation so that they ignore them. They get activated only when they encounter foreign antigens. The gut microbiota plays a major role in the maintenance of health. They help in digestion, absorption, and nutrition. These cells are foreign cells in the human body. They will be eliminated if they are recognized by the host immune system. So, there must be a mechanism to provide immune tolerance to these microbes. This immune tolerance is provided by stromal cells from the nearby lymph nodes. Even though they are not professional antigen-presenting cells, they exhibit normal-cell antigens to lymphocytes. Gut microbes also send specific signals that can be recognized by the immune system to provide tolerance.