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The polymeric immunoglobulin receptor: bridging innate and adaptive immune responses at mucosal surfaces
Author(s) -
Kaetzel Charlotte S.
Publication year - 2005
Publication title -
immunological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.839
H-Index - 223
eISSN - 1600-065X
pISSN - 0105-2896
DOI - 10.1111/j.0105-2896.2005.00278.x
Subject(s) - transcytosis , polymeric immunoglobulin receptor , secretory component , biology , innate immune system , immune system , immunoglobulin a , antibody , microbiology and biotechnology , antigen , receptor , secretion , j chain , immunology , acquired immune system , extracellular , immunoglobulin g , biochemistry , endocytosis
Summary: Secretory antibodies of the immunoglobulin A (IgA) class form the first line of antigen‐specific immune protection against inhaled, ingested, and sexually transmitted pathogens and antigens at mucosal surfaces. Epithelial transcytosis of polymeric IgA (pIgA) is mediated by the polymeric immunoglobulin receptor (pIgR). At the apical surface, the extracellular ligand‐binding region of pIgR, known as secretory component (SC), is cleaved and released in free form or as a component of secretory IgA (SIgA). SC has innate anti‐microbial properties, and it protects SIgA from proteolytic degradation. Expression of pIgR is regulated by microbial products through Toll‐like receptor signaling and by host factors such as cytokines and hormones. Recent studies of the structure of the extracellular ligand‐binding domain of pIgR have revealed mechanisms by which it binds pIgA and other ligands. During transcytosis, pIgA has been shown to neutralize pathogens and antigens within intracellular vesicular compartments. The recent identification of disease‐associated polymorphisms in human pIgR near the cleavage site may help to unravel the mystery of how pIgR is cleaved to SC. The identification of novel functions for SC and SIgA has expanded our view of the immunobiology of pIgR, a key component of the mucosal immune system that bridges innate and adaptive immune defense.