What is maintained by the mucosal immune system in addition to protection from pathogens?

The mucosal immune system plays a crucial role in the body’s defense by not only protecting against pathogens but also in maintaining tolerance to non-harmful antigens. This function is vital because it helps prevent unnecessary immune responses to benign substances, such as food proteins or commensal microorganisms present in the gut. By promoting tolerance, the mucosal immune system minimizes the risk of allergic reactions and autoimmune responses, which can occur if the immune system mistakenly attacks harmless substances.

Tolerance is achieved through various mechanisms, including the production of regulatory T cells that can suppress inappropriate immune responses. This balance is essential for maintaining homeostasis within the gut environment and ensuring that the body responds effectively to genuine threats while ignoring innocuous antigens.

In contrast, options that suggest increased susceptibility to diseases, a decrease in immune responses, or the promotion of harmful allergies misrepresent the critical functions of the mucosal immune system, as these would undermine the system's purpose in protecting and maintaining health.