Explain the origin of the secretory component and its significance after the release of dimeric IgA ...

During transcytosis the poly-Ig receptor is cleaved by a protease, leaving a small piece of the original receptor, called the secretory component, still bound to the J chain via disulfide bonds. Once dimeric IgA is released at the apical face, the carbohydrate moieties of the secretory component anchor the antibody to mucins of the mucus, enabling the antibodies to bind subsequently to microbes in the mucus and inhibit the ability of microbes to bind to and invade the mucosal epithelium of the gut. Instead, the microbe is expelled from the body via mucosal secretions in the feces.