ab17921 reacts with a reduction-resistant epitope present in both free and SIgA bound Secretory Component. It does not react with the cell lines lacking secretory component. The antibody is useful for studying the distribution and level of both free and bound secretory component. Secretory component is differentially expressed in epithelium, and the antibody is a popular marker for identifying subpopulations of epithelial cells and epithelial differentiation. The Secretory component antibody is a useful research tool for studying mucosal immunity, inflammation, remodeling, differentiation and tumorigenesis, all processes associated with differential secretory component expression.
The application notes include recommended starting dilutions; optimal dilutions/concentrations should be determined by the end user.
Use a concentration of 1 - 2 µg/ml.
1/50. Perform enzymatic antigen retrieval before commencing with IHC staining protocol.
IgA has two subclasses (IgA1 and IgA2) and can be produced as a monomeric as well as a dimeric form. The IgA dimeric form is the most prevalent and is also called secretory IgA (sIgA). The secretory component of sIgA protects the immunoglobulin from being degraded by proteolytic enzymes, thus sIgA can survive in the harsh gastrointestinal tract environment and provide protection against microbes that multiply in body secretions. sIgA can also inhibit inflammatory effects of other immunoglobulins.
Secretory component is a proteolytic cleavage product of the polymeric immunoglobulin receptor which remains associated with dimeric IgA in sero-mucus secretions. 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.
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.