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Proc Natl Acad Sci U S A. 2006 Apr 11;103(15):5941-6. Epub 2006 Apr 3.

Regulatory CD56(bright) natural killer cells mediate immunomodulatory effects of IL-2Ralpha-targeted therapy (daclizumab) in multiple sclerosis.

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Neuroimmunology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.


Administration of daclizumab, a humanized mAb directed against the IL-2Ralpha chain, strongly reduces brain inflammation in multiple sclerosis patients. Here we show that daclizumab treatment leads to only a mild functional blockade of CD4(+) T cells, the major candidate in multiple sclerosis pathogenesis. Instead, daclizumab therapy was associated with a gradual decline in circulating CD4(+) and CD8(+) T cells and significant expansion of CD56(bright) natural killer (NK) cells in vivo, and this effect correlated highly with the treatment response. In vitro studies showed that NK cells inhibited T cell survival in activated peripheral blood mononuclear cell cultures by a contact-dependent mechanism. Positive correlations between expansion of CD56(bright) NK cells and contraction of CD4(+) and CD8(+) T cell numbers in individual patients in vivo provides supporting evidence for NK cell-mediated negative immunoregulation of activated T cells during daclizumab therapy. Our data support the existence of an immunoregulatory pathway wherein activated CD56(bright) NK cells inhibit T cell survival. This immunoregulation has potential importance for the treatment of autoimmune diseases and transplant rejection and toward modification of tumor immunity.

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