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Updated: Jun 11, 2025

Analysis of Somatic Hypermutation in the JH4 intron of Germinal Center B cells from Mouse Peyer's Patches
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Published on: April 20, 2021

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CD5L associates with IgM via the J chain

Yuxin Wang1, Chen Su1, Chenggong Ji1

  • 1State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, P.R. China.

Nature Communications
|September 27, 2024
PubMed

CD5 antigen-like (CD5L), also known as Spα or AIM (Apoptosis inhibitor of macrophage), emerges as an integral component of serum immunoglobulin M (IgM). However, the molecular mechanism underlying the interaction between IgM and CD5L has remained elusive. In this study, we present a cryo-electron microscopy structure of the human IgM pentamer core in complex with CD5L. Our findings reveal that CD5L binds to the joining chain (J chain) in a Ca2+-dependent manner and further links to IgM via a disulfide bond. We further corroborate recently published data that CD5L reduces IgM binding to the mucosal transport receptor pIgR, but does not impact the binding of the IgM-specific receptor FcμR. Additionally, CD5L does not interfere with IgM-mediated complement activation. These results offer a more comprehensive understanding of IgM and shed light on the function of the J chain in the immune system.

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