Secretory IgA - Faecal

Description

Secretory IgA (sIgA) is found in high concentrations in the secretions of the gastrointestinal, genitourinary and respiratory mucosal linings. The most recognised function of sIgA includes its role in ‘immune exclusion’ in which it prevents viruses, bacteria and other antigens adhering to and penetrating epithelial mucosa. SIgA may also inhibit inflammatory processes that damage the mucosa and preliminary evidence suggests that it may play a role in inducing an antigen specific immune response by a non-inflammatory mechanism. A sIgA deficiency may lower resistance to infection.

The gastrointestinal, genitourinary and respiratory mucosal linings represent extensive surfaces for potential assault by microbes. Secretory IgA (sIgA) is found in high concentrations in the secretions that bathe these mucosal cells where it acts as the chief antibody in the first line of immune defence. It is a very stable molecule which is resistant to degradation and therefore functions well in the harsh environment of the gastrointestinal tract. SIgA is thought of predominantly as a first line of defence as part of the innate immune response, whereas serum IgA is part of the adaptive immune response. In comparison to serum IgA, the functions of sIgA (secretory IgA) are not dependent on the specificity of the IgA molecule.

SIgA can prevent antigens, including viruses, bacteria and bacterial toxins and enzymes, adhering to and penetrating the luminal epithelial mucosa. SIgA complexes with the antigens which facilitates their elimination by peristalsis or mucociliary movements.