IgA is the most common antibody class found in the mucus secretions that protect the mucous membranes. IgA can also be found in other secretions such as breast milk, passing immunity to newborns. Secretory IgA is assembled into a dimeric form with two monomers joined by a protein structure called the secretory component. One of the important functions of secretory IgA is to trap pathogens in mucus so that they can later be removed from the body.