Which immunoglobulin is the main secretory antibody in mucosal areas and typically exists as a dimer with a secretory component?

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The key idea is that mucosal immunity relies on secretory IgA, which is produced as a dimer connected by a J chain and transported across epithelial cells by the polymeric immunoglobulin receptor. As it moves to the mucosal surface, a portion of the receptor—the secretory component—remains attached to the IgA, forming secretory IgA. This secretory form is specialized for the harsh mucus environment and resists proteolysis, allowing it to neutralize pathogens right at the entry portals of the body. Other antibodies don’t fit this pattern: IgG is mainly a serum antibody, IgM is a pentamer not typically described as a mucosal secretory dimer with a secretory component, and IgE is involved in allergic responses and parasite defense rather than mucosal secretions. So the described antibody is secretory IgA.