International Immunology Advance Access originally published online on February 25, 2008
International Immunology 2008 20(4):499-508; doi:10.1093/intimm/dxn009
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PI3K is a negative regulator of IgE production
1 Department of Microbiology and Immunology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
2 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
3 Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
4 Present address: Department of Immunology and Genomic Medicine, Kyoto University Graduate School of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-6501, Japan
5 Present address: Department of Pharmacology, Kyoto University Graduate School of Medicine, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-6501, Japan
Correspondence to: S. Koyasu; E-mail: koyasu{at}sc.itc.keio.ac.jp
The production of IgE, a main player in allergic disorders such as asthma and atopic dermatitis, is strictly regulated and the serum concentrations of IgE are normally kept at a much lower level than other isotypes. We found that mice deficient for the p85
regulatory subunit of class IA phosphoinositide 3-kinase (PI3K) produced increasing amounts of serum IgE. Purified p85
–/– B cells produced more IgE than wild-type B cells in vitro in response to anti-CD40 mAb and IL-4. PI3K inhibitors wortmannin and IC87114 enhanced IgE production by wild-type B cells stimulated with anti-CD40 mAb and IL-4. Under the same condition, antigen receptor cross-linking induced the expression of inhibitor of differentiation-2 and suppressed the expression of activation-induced cytidine deaminase and class switch recombination (CSR) in a PI3K-dependent manner. IgE production was also suppressed in a concentrated cell culture condition, which was completely reversed by PI3K inhibition. The selective suppression of IgE production by PI3K was also observed at a protein level after CSR. Our results indicate that PI3K negatively regulates IgE production at both CSR and protein levels.
Keywords: AID, class switch recombination, Id2, IC87114, IgE, PI3K, wortmannin
Transmitting editor: T. Kurosaki
Received 17 September 2007, accepted 11 January 2008.
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