25-Hydroxycholesterol secreted by macrophages in response to Toll-like receptor activation suppresses immunoglobulin A production.

David R Bauman, Andrew D Bitmansour, Jeffrey G McDonald, Bonne M Thompson, Guosheng Liang, David W Russell

Department of Molecular Genetics and The Cancer Immunobiology Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.

Proceedings of the National Academy of Sciences of the United States of America 2009 Sep 29

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25-Hydroxycholesterol is produced in mammalian tissues. The function of this oxysterol is unknown. Here we describe a central role for 25-hydroxycholesterol in regulating the immune system. In initial experiments, we found that stimulation of macrophage Toll-like receptors (TLR) induced expression of cholesterol 25-hydroxylase and the synthesis of 25-hydroxycholesterol. Treatment of naïve B cells with nanomolar concentrations of 25-hydroxycholesterol suppressed IL-2-mediated stimulation of B cell proliferation, repressed activation-induced cytidine deaminase (AID) expression, and blocked class switch recombination, leading to markedly decreased IgA production. Consistent with these findings, deletion of the mouse cholesterol 25-hydroxylase gene caused an increase in serum IgA. Conversely, inactivation of the CYP7B1 oxysterol 7alpha-hydroxylase, which degrades 25-hydroxycholesterol, decreased serum IgA. The suppression of IgA class switching in B cells by a macrophage-derived sterol in response to TLR activation provides a mechanism for local and systemic negative regulation of the adaptive immune response by the innate immune system.

Citation

David R Bauman, Andrew D Bitmansour, Jeffrey G McDonald, Bonne M Thompson, Guosheng Liang, David W Russell. 25-Hydroxycholesterol secreted by macrophages in response to Toll-like receptor activation suppresses immunoglobulin A production. Proceedings of the National Academy of Sciences of the United States of America. 2009 Sep 29;106(39):16764-9