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Abstract

Mucosal immunity is the first line of defense against pathogens at the mucosal surfaces of the body, including the gastrointestinal, respiratory, and urogenital tracts. The immune system in these areas is uniquely specialized to provide both protection against pathogens and tolerance to harmless antigens, such as food proteins and commensal microorganisms. Central to mucosal immunity are T cells and B cells, which orchestrate both defense and tolerance mechanisms. T-cell responses in the mucosal environment involve the activation and differentiation of various subsets, including Th1, Th2, Th17, and regulatory T cells (Tregs). B cells, particularly those in mucosal-associated lymphoid tissues (MALT), play an important role in producing secretory IgA (sIgA), the dominant antibody class in mucosal defense. This review discusses the interplay between T-cell and B-cell responses in mucosal immunity, focusing on their roles in immune defense against pathogens and the establishment of immune tolerance. We explore the cellular and molecular mechanisms that govern these responses, the balance between immunity and tolerance, and the implications for health and disease, including inflammatory bowel disease (IBD), allergies, and autoimmunity.