The secretory component is a component of immunoglobulin A

Immunoglobulin A

Immunoglobulin A is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combined; between three and five grams are secreted into the intestinal lumen each day....

 (IgA) which consists of a portion of the polymeric immunoglobulin receptor

Polymeric immunoglobulin receptor

Polymeric immunoglobulin receptor is a protein that in humans is encoded by the PIGR gene.It is a Fc receptor which facilitates the secretion of immunoglobulin A and immunoglobulin M.-Further reading:-External links:...

. Polymeric IgA binds to the polymeric immunoglobulin receptor on the basolateral surface of epithelial cells and is taken up into the cell via transcytosis

Transcytosis

Transcytosis is the process by which various macromolecules are transported across the interior of a cell. Vesicles are employed to intake the macromolecules on one side of the cell, draw them across the cell, and eject them on the other side. While transcytosis is most commonly observed in cells...

. The receptor-IgA complex passes through the cellular compartments before being secreted on the luminal surface

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

 of the epithelial cells, still attached to the receptor. Proteolysis

Proteolysis

Proteolysis is the directed degradation of proteins by cellular enzymes called proteases or by intramolecular digestion.-Purposes:Proteolysis is used by the cell for several purposes...

of the receptor occurs and the dimeric IgA molecule, along with the secretory component, are free to diffuse throughout the lumen.