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Publication Abstract from PubMed

Polymeric immunoglobulins are essential components of the immune system in jawed vertebrates. While mammalian immunoglobulin M (IgM) typically forms a pentamer linked by the joining chain (J-chain), Xenopus laevis IgX can assemble into a J-chain-independent polymer. Here, we present the cryo-electron microscopy (cryo-EM) structure of IgX, revealing its hexameric configuration. By incorporating the IgX tailpiece into human IgM, we achieved efficient IgM hexamer formation. Truncating IgM's natural tailpiece to a range of 11 to 16 residues also substantially enhanced hexamerization efficiency. Furthermore, introducing a shortened IgM tailpiece to IgG resulted in effective IgG hexamer formation. We further show that the engineered IgM and IgG hexamers targeting CD20 demonstrated robust complement-dependent cytotoxicity (CDC) against several B lymphoma cells. In addition, the IgG-Fc hexamer functioned as a decoy, attenuating CDC in cell cultures. These findings deepen our understanding of polymeric immunoglobulin evolution and introduce innovative strategies for the development of IgM- and IgG-based biologics.

Xenopus IgX informs engineering strategies of IgM and IgG hexamers.,Zhang R, Ji C, Li S, Li N, Gao N, Xiao J Sci Adv. 2025 Nov 7;11(45):eaea3737. doi: 10.1126/sciadv.aea3737. Epub 2025 Nov , 5. PMID:41191733^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.