Research Article

Structure of the secretory immunoglobulin A core

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Science  06 Feb 2020:
eaaz5807
DOI: 10.1126/science.aaz5807

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Abstract

Secretory immunoglobulin A (sIgA) represents the immune system’s first-line of defense against mucosal pathogens. IgAs are transported across the epithelium, as dimers and higher-order polymers, by the polymeric immunoglobulin receptor (pIgR). Upon reaching the luminal side, sIgAs mediate host protection and pathogen neutralization. In recent years, an increasing amount of attention has been given to IgA as a novel therapeutic antibody. Despite extensive studies sIgA structures have remained elusive. Here, we determine the atomic-resolution structures of dimeric, tetrameric, and pentameric IgA-Fc linked by the joining chain (JC) and in complex with the secretory component of the pIgR. We suggest a mechanism where the JC templates IgA oligomerization and imparts asymmetry for pIgR binding and transcytosis. This framework will inform the design of future IgA-based therapeutics.

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