Secretory component
The secretory component is a component of immunoglobulin A (IgA) which consists of a portion of the polymeric immunoglobulin receptor. Polymeric IgA binds to the polymeric immunoglobulin receptor on the basolateral surface of epithelial cells and is taken up into the cell via transcytosis. The receptor-IgA complex passes through the cellular compartments before being secreted on the luminal surface of the epithelial cells, still attached to the receptor. Proteolysis of the receptor occurs and the dimeric IgA molecule, along with the secretory component, are free to diffuse throughout the lumen.[1]
Secretory components wrap 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. This property is especially important in the transfer of immune system components during breastfeeding. [2]
External links
- Secretory component at the US National Library of Medicine Medical Subject Headings (MeSH)
References
- ↑ CS Kaetzel, JK Robinson, KR Chintalacharuvu, JP Vaerman, and ME Lamm (1991). "The polymeric immunoglobulin receptor (secretory component) mediates transport of immune complexes across epithelial cells: a local defense function for IgA". Proc Natl Acad Sci USA 88 (19): 8796–8800. doi:10.1073/pnas.88.19.8796. PMC 52597. PMID 1924341.
- ↑ Newman, Jack (December 1995). "How Breast Milk Protects Newborns". Scientific American: 76–80.