Structure of the human secretory immunoglobulin M core.

Nikit Kumar, Christopher P Arthur, Claudio Ciferri, Marissa L Matsumoto

Structure (London, England : 1993) 2021 Jun 03

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Immunoglobulins (Ig) A and M are the only human antibodies that form oligomers and undergo transcytosis to mucosal secretions via the polymeric Ig receptor (pIgR). When complexed with the J-chain (JC) and the secretory component (SC) of pIgR, secretory IgA and IgM (sIgA and sIgM) play critical roles in host-pathogen defense. Recently, we determined the structure of sIgA-Fc which elucidated the mechanism of polymeric IgA assembly and revealed an extensive binding interface between IgA-Fc, JC, and SC. Despite low sequence identity shared with IgA-Fc, IgM-Fc also undergoes JC-mediated assembly and binds pIgR. Here, we report the structure of sIgM-Fc and carryout a systematic comparison to sIgA-Fc. Our structural analysis reveals a remarkably conserved mechanism of JC-templated oligomerization and SC recognition of both IgM and IgA through a highly conserved network of interactions. These studies reveal the structurally conserved features of sIgM and sIgA required for function in mucosal immunity. Copyright © 2021 Elsevier Ltd. All rights reserved.

Citation

Nikit Kumar, Christopher P Arthur, Claudio Ciferri, Marissa L Matsumoto. Structure of the human secretory immunoglobulin M core. Structure (London, England : 1993). 2021 Jun 03;29(6):564-571.e3