Secretory IgA is comprised of two immunglobuline A molecules, which are joined by a J-protein and a secretory component. The secretory component is synthesized by epithelial cells of the mucous membrane of gastrointestinal, respiratory and urogenitaltract. It is also produced by the saliva, tear and mammary glands. The plasma cells in the subendothelial area of mucous membranes are releasing a complex of two IgA-molecules, which are joined over the J-protein. This complex is binding to a secretory component, located at the surface of the epithel cell. After binding, the sIgA is transported across the cell and excreted by exocytosis.
The determination of secretory IgA (sIgA) allows a first overview of the functionality of the gastrointestinal associated immune system (GALT). At this the secretory power and the degree of stimulation of the plasma cells of the intestinal submucosa is determined.
Sample volume 100 mg, 100 µl
Calibration 5 point
Incubation time 1h, 1h, 15 min
Principle of the method
The sIgA-ELISA test determines human secretory IgA according to the “sandwich”-principle. sIgA in sample, standard and controls binds to antibodies, which are coated to the microtiterplate. After a washing step a peroxidase labeled detection antibody is added. A second washing step is followed by the addition of the substrate which is converted to a colored product by the peroxidase. The reaction is terminated by the addition of an acidic stop solution. The optical densities are read at 450 nm (against teh reference wavelength 620 nm) in a microtiterplate reader. The sIgA concentration can be calculated from the standard curve.