Structure of the secretory immunoglobulin A core

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Secretory immunoglobulin A (sIgA) is crucial for mucosal immunity, neutralizing pathogens.
• The polymeric immunoglobulin receptor (pIgR) transports IgA across epithelia.
• Understanding sIgA structure is key for developing IgA-based therapeutics.

Purpose of the Study:

• To determine the atomic resolution structures of IgA-Fc oligomers.
• To elucidate the role of the joining chain (JC) in IgA oligomerization and pIgR binding.
• To provide a structural framework for IgA-based therapeutic design.

Main Methods:

• Atomic resolution structure determination of dimeric, tetrameric, and pentameric IgA-Fc.
• Analysis of IgA-Fc in complex with the secretory component of pIgR.
• Structural modeling to propose a mechanism for IgA transport.

Main Results:

• Atomic structures of dimeric, tetrameric, and pentameric IgA-Fc were resolved.
• The joining chain (JC) was shown to template IgA oligomerization.
• A mechanism for JC-mediated asymmetry in pIgR binding and transcytosis was proposed.

Conclusions:

• The JC is critical for IgA oligomerization and dictates asymmetry for pIgR interaction.
• These structural insights provide a foundation for engineering novel IgA therapeutics.
• This work advances our understanding of mucosal immunity mechanisms.