Which immunoglobulin is predominantly involved in mucosal immunity?

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Answer: (A)

Secretory IgA is the antibody class most important for mucosal defense. It’s produced in mucosal tissues and transported across the epithelium as a dimer with a secretory component that shields it from stomach and intestinal proteases. In secretions like saliva, mucus, and tears, secretory IgA neutralizes pathogens and toxins and prevents them from sticking to or invading mucosal surfaces, helping to keep the lumen relatively free of infection without provoking strong inflammation. Other antibodies serve different roles: IgG is mainly systemic and handles opsonization and intracellular neutralization; IgM is the early responder with strong agglutination and complement activation; IgE is involved in allergic responses and defense against parasites. Thus IgA is best suited for protecting mucosal surfaces.