secretory component


se·cre·to·ry com·po·nent

a polypeptide chain found in external secretions (for example, tears, saliva, colostrum) associated with immunoglobulins A and M. It also may occur in free form but when attached to dimeric IgA, it facilitates transport across the mucosal epithelial surface. The secretory piece is derived by proteolytic cleavage of the immunoglobulin receptor on epithelial cells.