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Shared parts, different structures: How asymmetry drives IgM and IgA structure-function relationships
Rebecca M Schneider1, Yujia Ji2, Beth M Stadtmueller3
1Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, 61801, USA; Carl R. Woese Institute of Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, 61801, USA.
Current Opinion in Structural Biology
|August 4, 2026
Summary
Polymeric immunoglobulins (pIgs) and secretory immunoglobulins (SIgs) are key to vertebrate immunity. Recent cryo-EM studies reveal their complex, asymmetric structures, advancing understanding of immune function.
Area of Science:
- Immunology
- Structural Biology
- Biochemistry
Background:
- Polymeric immunoglobulins (pIgs) and secretory immunoglobulins (SIgs) are crucial for vertebrate immune responses.
- These antibody forms possess unique functions in circulation and mucosal barriers, respectively.
- Their complex molecular structures were largely unknown before recent advancements.
Purpose of the Study:
- To elucidate the structural basis of polymeric and secretory immunoglobulin function.
- To understand the conformational diversity and asymmetry of pIgs and SIgs.
- To establish a foundation for exploring pIg and SIg structure-function relationships in immunity.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was utilized to determine high-resolution structures.
- Analysis of complexes formed between immunoglobulins and host receptors or pathogens.
- Comparative structural analysis across different species.
Main Results:
- Cryo-EM revealed secretory IgA (SIgA) and secretory IgM (SIgM) as remarkably asymmetric assemblies.
- New insights into IgM and IgA complexes with host receptors and virulence factors were uncovered.
- Species-specific structural variations and conformational links between pIg cores and antigen-binding fragments were identified.
Conclusions:
- Conformational asymmetry is a key characteristic of polymeric and secretory immunoglobulins.
- These structural findings provide critical insights into immunoglobulin function in immunity.
- The study lays the groundwork for future research on immunoglobulin structure-function relationships.
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Overview
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