Rat bile as a convenient source of secretory IgA and free secretory component

Abstract
Rat hepatic bile contains three proteins as major constituents: secretory IgA (SIgA), free secretory component (FSC) and albumin. Traces of α-macroglo-bulin, transferrin, IgG and IgM are also detectable. The bile duct daily pours between 5–12 mg each of SIgA and FSC into the rat duodenum. The origin and function of these proteins in bile may represent important clues in the understanding. of the SIgA system.