Secretory immunoglobulin A: well beyond immune exclusion at mucosal surfaces.
At mucosal surfaces, secretory IgA (SIgA) antibodies serve as the first line of defense against microorganisms through a mechanism called immune exclusion that prevents interaction of neutralized antigens with the epithelium. In addition, SIgA plays a role in the immune balance of the epithelial barrier through selective adhesion to M cells in intestinal Peyer's patches. This mediates the transepithelial retro-transport of the antibody and associated antigens from the intestinal lumen to underlying gut-associated organized lymphoid tissue. In Peyer's patches, SIgA-based immune complexes are internalized by underlying antigen-presenting cells, leaving the antigen with masked epitopes, a form that limits the risk of overwhelming the local immune protection system with danger signals. This translates into the onset of mucosal and systemic responses associated with production of anti-inflammatory cytokines and limited activation of antigen-presenting cells. In the gastrointestinal tract, SIgA exhibits thus properties of a neutralizing agent (immune exclusion) and of an immunopotentiator inducing effector immune responses in a noninflammatory context favorable to preserve local homeostasis.
Corthësy
Blaise
B
R & D Laboratory, Division of Immunology and Allergy, University State Hospital (CHUV), Lausanne, Switzerland. blaise.corthesy@chuv.ch
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D000941:Antigens / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D041981:Gastrointestinal Tract / Q000276:immunology; D007071:Immunoglobulin A, Secretory / Q000276:immunology*; D007413:Intestinal Mucosa / Q000276:immunology*; D051379:Mice; D010581:Peyer's Patches / Q000276:immunology
D000941:Antigens; D016207:Cytokines; D007071:Immunoglobulin A, Secretory