What is mucosal immunity and which antibody is most involved?

• A. System of immune protection at mucosal surfaces, primarily mediated by secretory IgA
• B. Protection of skin surfaces by IgG
• C. Systemic immunity mediated by IgM
• D. Mucosal immunity is not related to antibodies

Answer: (A)

The concept here is mucosal immunity, the immune protection at mucosal surfaces such as the lining of the gut, airways, and other moist membranes. The antibody most involved is secretory IgA. In mucosal tissues, plasma cells produce IgA that is transported across the epithelium and released into secretions as secretory IgA. This form is particularly well-suited for mucosal defenses because it can neutralize viruses and toxins in the lumen, prevent pathogens from attaching to and invading mucosal cells, and it tends to do so without triggering strong inflammatory reactions. The secretory component protects IgA from being degraded in secretions, helping it function effectively in these environments. In short, mucosal immunity is the protective system at mucosal surfaces, with secretory IgA as the primary antibody mediating it. The other statements describe protections or immune components outside mucosal contexts or systemic immunity, which is why they don’t fit.