Author(s): Weller S, Faili A, Garcia C, Braun MC, Le Deist F F,
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Abstract Somatically mutated IgM(+)-only and IgM(+)IgD(+)CD27(+) B lymphocytes comprise approximately 25\% of the human peripheral B cell pool. These cells phenotypically resemble class-switched B cells and have therefore been classified as postgerminal center memory B cells. X-linked hyper IgM patients have a genetic defect characterized by a mutation of the CD40L gene. These patients, who do not express a functional CD40 ligand, cannot switch Ig isotypes and do not form germinal centers and memory B cells. We report here that an IgM(+)IgD(+)CD27(+) B cell subset with somatically mutated Ig receptors is generated in these patients, implying that these cells expand and diversify their Ig receptors in the absence of classical cognate T-B collaboration. The presence of this sole subset in the absence of IgM(+)-only and switched CD27(+) memory B cells suggests that it belongs to a separate diversification pathway.
This article was published in Proc Natl Acad Sci U S A
and referenced in Journal of Clinical & Cellular Immunology