Human blood IgM "memory" B cells are circulating splenic marginal zone B cells harboring a prediversified immunoglobulin repertoire.

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Weller, Sandra | Braun, Moritz, C. | Tan, Bruce, K. | Rosenwald, Andreas | Cordier, Corinne | Conley, Mary Ellen | Plebani, Alessandro | Kumararatne, Dinakhanta, S. | Bonnet, Damien | Tournilhac, Olivier | Tchernia, Gil | Steiniger, Birte | Staudt, Louis, M. | Casanova, Jean-Laurent | Reynaud, Claude-Agnès | Weill, Jean-Claude

Edité par CCSD ; American Society of Hematology -

International audience. The human peripheral B-cell compartment displays a large population of immunoglobulin M-positive, immunoglobulin D-positive CD27(+) (IgM(+)IgD(+)CD27(+)) "memory" B cells carrying a mutated immunoglobulin receptor. By means of phenotypic analysis, complementarity-determining region 3 (CDR3) spectratyping during a T-independent response, and gene-expression profiling of the different blood and splenic B-cell subsets, we show here that blood IgM(+)IgD(+)CD27(+) cells correspond to circulating splenic marginal zone B cells. Furthermore, analysis of this peripheral subset in healthy children younger than 2 years shows that these B cells develop and mutate their immunoglobulin receptor during ontogeny, prior to their differentiation into T-independent antigen-responsive cells. It is therefore proposed that these IgM(+)IgD(+)CD27(+) B cells provide the splenic marginal zone with a diversified and protective preimmune repertoire in charge of the responses against encapsulated bacteria.

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