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Blood. 2011 Jun 2;117(22):5870-80. doi: 10.1182/blood-2010-09-310318. Epub 2011 Apr 11.

CD300a is expressed on human B cells, modulates BCR-mediated signaling, and its expression is down-regulated in HIV infection.

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  • 1Receptor Cell Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20892, USA.

Abstract

The immunomodulatory receptor CD300a is expressed on human B cells. Naive B cells express very low levels of this receptor, whereas memory B cells and plasmablasts/cells express variable levels of CD300a. Germinal center B cells are negative for CD300a expression. Stimulation of naive B cells via B-cell receptor (BCR) and Toll-like receptor 9, along with T-cell help, failed to up-regulate CD300a cell surface expression despite the increased expression of the memory marker CD27 and the down-regulation of CD305. However, Toll-like receptor 9 stimulation alone significantly increased CD300a expression on memory B cells, whereas interleukin-4 and transforming growth factor-β1 act as negative regulators of CD300a expression on memory B cells. Coligation of BCR and CD300a inhibits Ca(2+) mobilization and nuclear factor of activated T cell transcriptional activity evoked by BCR ligation alone. Suppression of CD300a expression in primary B cells with siRNA resulted in increased BCR-mediated proliferation, thereby confirming the inhibitory capacity of CD300a. Finally, we show that CD300a expression levels are significantly down-regulated in the circulating B cells of HIV-infected patients. Altogether, these data demonstrate a novel mechanism for suppressing the activity of B cells and suggest a potential role for CD300a in the B-cell dysfunction observed in HIV-induced immunodeficiency.

PMID:
21482706
[PubMed - indexed for MEDLINE]
PMCID:
PMC3112036
Free PMC Article

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