Magri, GiulianaComerma, LauraPybus, MarcSintes, JordiLligé, DavidSegura-Garzón, DanielBascones, SabrinaYeste, AdaGrasset, Emilie K.Gutzeit, CindyUzzan, MathieuRamanujam, Meeravan Zelm, Menno C.Albero González, RaquelVazquez, IvonneIglesias, MarSerrano, SergiMárquez, LucíaMercadé Gil, M. ElenaMehandru, SaurabhCerutti, Andrea2020-07-172020-07-172017-071074-7613https://hdl.handle.net/2445/168922Secretory immunoglobulin A (SIgA) enhances host-microbiota symbiosis, whereas SIgM remains poorly understood. We found that gut IgM+ plasma cells (PCs) were more abundant in humans than mice and clonally related to a large repertoire of memory IgM+ B cells disseminated throughout the intestine but rare in systemic lymphoid organs. In addition to sharing a gut-specific gene signature with memory IgA+ B cells, memory IgM+ B cells were related to some IgA+ clonotypes and switched to IgA in response to T cell-independent or T cell-dependent signals. These signals induced abundant IgM which, together with SIgM from clonally affiliated PCs, recognized mucus-embedded commensals. Bacteria recognized by human SIgM were dually coated by SIgA and showed increased richness and diversity compared to IgA-only-coated or uncoated bacteria. Thus, SIgM may emerge from pre-existing memory rather than newly activated naive IgM+ B cells and could help SIgA to anchor highly diverse commensal communities to mucus.17 p.application/pdfengcc-by-nc-nd (c) Elsevier, 2017http://creativecommons.org/licenses/by-nc-nd/3.0/esCèl·lules BMucosa gastrointestinalB cellsGastrointestinal mucosainfo:eu-repo/semantics/article6730422020-07-17info:eu-repo/semantics/openAccess28709802