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,
* Center for Pulmonary and Infectious Disease Control,
Departments of Microbiology and Immunology and
Department of Medicine, University of Texas Health Center, Tyler, TX 75708l; and
Amgen, Seattle, WA 98101
We evaluated the capacity of NK cells to influence expansion of CD4+CD25+FoxP3+ regulatory T cells (Tregs) in response to microbial Ags, using Mycobacterium tuberculosis as a model. We previously found that Tregs expand when CD4+ cells and monocytes are exposed to M. tuberculosis. Addition of NK cells that were activated by monokines (IL-12, IL-15, and IL-18) or by exposure to M. tuberculosis-stimulated monocytes reduced Treg expansion in response to M. tuberculosis. NK cell inhibition of Treg expansion was not mediated through IFN-
. Activated NK cells lysed expanded, but not freshly isolated Tregs. Although monokines increased NK cell expression of the activating receptors NKp46, NKG2D, 2B4, CD16, and DNAM-1, only anti-NKG2D and anti-NKp46 inhibited NK cell lysis of expanded Tregs. Of five NKG2D ligands, only UL16-binding protein 1 (ULBP1) was up-regulated on M. tuberculosis-expanded Tregs, and anti-ULBP1 inhibited NK cell lysis of expanded Tregs. M. tuberculosis-stimulated monocytes activated NK cells to lyse expanded Tregs, and this was also inhibited by anti-NKG2D and anti-ULBP1, confirming the physiological relevance of this effect. Our study identifies a potential new role for NK cells in maintaining the delicate balance between the regulatory and effector arms of the immune response.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported by grants from the National Institutes of Health (AI054629 and A1063514), the Cain Foundation for Infectious Disease Research, and the Center for Pulmonary and Infectious Disease Control. P.F.B. holds the Margaret E. Byers Cain Chair for Tuberculosis Research.
2 Address correspondence and reprint requests to Dr. Ramakrishna Vankayalapati, Center for Pulmonary and Infectious Disease Control, University of Texas Health Center, 11937 U.S. Highway 271, Tyler, TX 75708-3154. E-mail address: Krishna.vankayalapati{at}uthct.edu
3 Abbreviations used in this paper: Treg, regulatory T cell; MIC, MHC class I-related chain; ULBP, UL16-binding protein; TB, tuberculosis; MFI, mean fluorescence intensity; 7-AAD, 7-aminoactinomycin D; WCL, whole cell lysate.
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