In probing the cell of origin in malignant B cells, an imprint of somatic hypermutation (SHM) in immunoglobulin (Ig) variable (V) region genes delineates antigen encounter, and identifying the precise pathway generating SHM in the normal B-cell counterpart becomes relevant. SHM remains the definitive memory imprint in normal human B cells, but CD27 expression also delineates memory. Recently, dye extrusion adenosine triphosphate-binding transporter assays identified circulating isotype-switched memory B cells that lacked CD27, yet exhibited low levels of SHM. To extend findings, we report a pre-switched CD27(-ve) circulating memory B-cell population in normal blood using comparable assays, and isolated CD19(+)IgM(+)D(+)CD27(-ve) cells (>99\% purity) for the analysis of IGHV5/IGHV3-IGHM transcripts. Of these (n=334), approximately 78\% were germ line and naive B cell derived. Strikingly, 21.9\% of the transcripts were mutated. They showed 3-5 mutations (13.5\% of sequences) and >5 mutations (8.4\% of sequences) per transcript. Accrual of mutations in a subset of CD19(+)IgM(+)D(+)CD27(-ve) cells define a new circulating pre-switched memory B-cell pool, present in substantial numbers in the population harboring naive B cells. These CD19(+)IgM(+)D(+)CD27(-ve) memory B cells may have a distinct lineage and function, and seem relevant to understanding origins of malignant B cells, in particular those of hairy cell leukemia cells, which display mutated V genes yet lack CD27 expression.
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|Titolo:||Defining origins of malignant B cells: a new circulating normal human IgM(+)D(+) B-cell subset lacking CD27 expression and displaying somatically mutated IGHV genes as a relevant memory population.|
|Citazione:||N., W.B., M., T., G. D., G., Forconi, F., & S. S., S. (2009). Defining origins of malignant B cells: a new circulating normal human IgM(+)D(+) B-cell subset lacking CD27 expression and displaying somatically mutated IGHV genes as a relevant memory population. LEUKEMIA, 23, 2075-2080.|
|Appare nelle tipologie:||1.1 Articolo in rivista|
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