International Immunology Advance Access originally published online on July 5, 2004
International Immunology 2004 16(8):1161-1171; doi:10.1093/intimm/dxh116
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© 2004 The Japanese Society for Immunology
ORIGINAL RESEARCH PAPERS |
BASH-deficient mice: limited primary repertoire and antibody formation, but sufficient affinity maturation and memory B cell generation, in anti-NP response
1 Division of Molecular Biology and 2 Division of Biosignaling, Research Institute for Biological Sciences, Tokyo University of Science, Yamazaki 2669, Noda, Chiba 278-0022, Japan
3 Present address: Department of Molecular Embryology, Research Institute, Osaka Medical Center for Maternal and Child Health, 840, Murodo-cho, Izumi, Osaka 594-1101, Japan
4 Present address: Age Dimension Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 6, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan
Correspondence to: D. Kitamura; E-mail: kitamura{at}rs.noda.tus.ac.jp
Signaling through the B cell antigen receptor (BCR) induces activation and proliferation of B cells, a response that requires the adaptor protein BASH (also known as BLNK/SLP-65). Although BASH and other molecules, such as Btk, PLC
2 and PKCß, are known to be essential for T cell-independent immune responses in vivo, their requirement during T cell-dependent immune responses, especially their role in antibody affinity-maturation and memory B cell generation remains unclear. In this study, we examined primary and memory immune responses to the T cell-dependent hapten antigen, (4-hydroxy-3-nitrophenyl)acetyl (NP) conjugated to chicken gammaglobulin (CGG), in BASH-deficient mice on a C57BL/6 background. In the primary response, NP-specific IgM was barely produced and the typical anti-NP IgG1/
production was markedly attenuated, but 
chain was unexpectedly over-represented in the anti-NP antibodies. In contrast, CGG-specific IgG1 was normally produced. In the memory response, IgG1/ antibody with high affinity to NP was produced at normal level in the mutant mice. The frequency and distribution of somatic mutations in the VH186.2 genes of the anti-NP IgG1/ antibody were also normal. These results indicate that BASH-mediated BCR signaling is dispensable for somatic hypermutation and affinity selection, as well as generation and response of memory B cells. Interestingly, mutated VH genes with the same clonal origin were prominent in the anti-NP antibodies of BASH-deficient mice, indicating that a limited number of original clones had been recruited into the memory compartment. Thus, the scarcity of specific clones in the primary repertoire and an impaired primary response is not detrimental to the quality and quantity of a memory response.
Keywords: adaptor protein, affinity maturation, B cell antigen receptor, signal transduction, somatic hypermutation
Transmitting editor: T. Watanabe
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