Secretory Component

The secretory component (SC) is a unique polypeptide chain that may be found in immunoglobulins A and M (IgA and IgM). The SC wraps around two IgA units joined by a J chain protein fragment, resulting in a configuration with each of the two antigen binding regions of the two constituent y-shaped antibodies exposed. One identified function of secretory components is to protect IgA antibodies from degradation by the gastric acids and enzymes of the digestive system. It also appears that SC may serve in the three-dimensional organization or in the transport and distribution of the resulting IgA complexes.