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J Immunol. 2017 Nov 1;199(9):3023-3030. doi: 10.4049/jimmunol.1700868. Epub 2017 Sep 22.

Efficient Induction of Ig Gene Hypermutation in Ex Vivo-Activated Primary B Cells.

Author information

1
Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
2
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
3
Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, Yokohama 226-8502, Japan.
4
Shiga Medical Center Research Institute, Shiga 524-8524, Japan; and.
5
Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
6
Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China; wang@fudan.edu.cn.

Abstract

Activation-induced cytidine deaminase (AID) initiates both somatic hypermutation (SHM) and class switch recombination (CSR) of Ig genes. How AID is targeted to the Ig V gene and switch region to trigger SHM and CSR remains elusive. Primary B cells stimulated with CD40L plus IL-4 or LPS plus IL-4 undergo efficient CSR, but it has been difficult to induce SHM in these cells. In the current study, we used B cells from B1-8hi mice carrying a prerecombined VH186.2DFL16.1JH2 Ab gene to investigate the induction of SHM under in vitro culture conditions. B1-8hi splenic B cells stimulated with CD40L plus IL-4 or LPS plus IL-4 underwent robust CSR to IgG1, but failed to generate SHM in the VH186.2 gene. Remarkably, ectopic expression of AID in AID-deficient, but not wild-type, B1-8hi B cells induced efficient SHM at a rate close to that observed in germinal center B cells. We further established an AID-deficient CH12 B lymphoma line and found that ectopic expression of AID in the mutant line, but not in AID-sufficient CH12 cells, induced efficient point mutations and deletions in the V gene. These results demonstrate that the endogenous AID in ex vivo-activated primary B and B lymphoma cells not only cannot induce SHM but also inhibit the induction of SHM by the exogenous AID. Our results further suggest that the spatiotemporal distribution and/or posttranslational modification of AID strongly affects the induction of SHM in ex vivo-activated primary B cells.

PMID:
28939756
DOI:
10.4049/jimmunol.1700868
[Indexed for MEDLINE]
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