While both serum IgA and sIgA share the basic IgA structure, they differ in form and function. Serum IgA is mainly monomeric and circulates in the bloodstream, contributing to systemic immunity. In contrast, sIgA is a dimer with a protective secretory component, specially adapted to function in mucosal environments. This adaptation allows sIgA to resist proteolytic degradation and maintain its activity in secretions, where it exerts its immune protective functions.
