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Proc Natl Acad Sci U S A. 2014 Sep 30;111(39):E4119-26. doi: 10.1073/pnas.1415866111. Epub 2014 Sep 16.

B-1a transitional cells are phenotypically distinct and are lacking in mice deficient in IκBNS.

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Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; and.
Center for Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX 75390-8505
Department of Microbiology, Tumor, and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; and


B-1 cells mediate early protection against infection by responding to T cell-independent (TI) antigens found on the surface of various pathogens. Mice with impaired expression of the atypical IκB protein IκBNS have markedly reduced frequencies of B-1 cells. We used a mouse strain with dysfunctional IκBNS derived from an N-ethyl-N-nitrosourea (ENU) screen, named bumble, to investigate the point in the development of B-1 cells where IκBNS is required. The presence of wild-type (wt) peritoneal cells in mixed wt/bumble chimeras did not rescue the development of bumble B-1 cells, but wt peritoneal cells transferred to bumble mice restored natural IgM levels and response to TI antigens. The bumble and wt mice displayed similar levels of fetal liver B-1 progenitors and splenic neonatal transitional B (TrB) cells, both of which were previously shown to give rise to B-1 cells. Interestingly, we found that a subset of wt neonatal TrB cells expressed common B-1a markers (TrB-1a) and that this cell population was absent in the bumble neonatal spleen. Sorted TrB-1a (CD93(+)IgM(+)CD5(+)) cells exclusively generated B-1a cells when adoptively transferred, whereas sorted CD93(+)IgM(+)CD5(-) cells gave rise to B-2 cells and, to a lesser extent, B-1b and B-1a cells. This study identifies a phenotypically distinct splenic population of TrB-1a cells and establishes that the development of B-1a cells is blocked before this stage in the absence of IκBNS.


B-1b; IκB-δ; NF-κB1; NP-ficoll; Nfkbid

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