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      Regulation of neutrophils by interferon-γ limits lung inflammation during tuberculosis infection

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      The Journal of Experimental Medicine
      The Rockefeller University Press

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          Abstract

          IFN-γ functions to suppress neutrophil accumulation in the lungs of mice infected with M. tuberculosis, in part by suppressing IL-17 production from CD4 + T cells.

          Abstract

          Resistance to Mycobacterium tuberculosis requires the host to restrict bacterial replication while preventing an over-exuberant inflammatory response. Interferon (IFN) γ is crucial for activating macrophages and also regulates tissue inflammation. We dissociate these two functions and show that IFN-γ −/− memory CD4 + T cells retain their antimicrobial activity but are unable to suppress inflammation. IFN-γ inhibits CD4 + T cell production of IL-17, which regulates neutrophil recruitment. In addition, IFN-γ directly inhibits pathogenic neutrophil accumulation in the infected lung and impairs neutrophil survival. Regulation of neutrophils is important because their accumulation is detrimental to the host. We suggest that neutrophilia during tuberculosis indicates failed Th1 immunity or loss of IFN-γ responsiveness. These results establish an important antiinflammatory role for IFN-γ in host protection against tuberculosis.

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          Most cited references57

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          IL-23 and IL-17 in the establishment of protective pulmonary CD4+ T cell responses after vaccination and during Mycobacterium tuberculosis challenge.

          Interferon-gamma is key in limiting Mycobacterium tuberculosis infection. Here we show that vaccination triggered an accelerated interferon-gamma response by CD4(+) T cells in the lung during subsequent M. tuberculosis infection. Interleukin 23 (IL-23) was essential for the accelerated response, for early cessation of bacterial growth and for establishment of an IL-17-producing CD4(+) T cell population in the lung. The recall response of the IL-17-producing CD4(+) T cell population occurred concurrently with expression of the chemokines CXCL9, CXCL10 and CXCL11. Depletion of IL-17 during challenge reduced the chemokine expression and accumulation of CD4(+) T cells producing interferon-gamma in the lung. We propose that vaccination induces IL-17-producing CD4(+) T cells that populate the lung and, after challenge, trigger the production of chemokines that recruit CD4(+) T cells producing interferon-gamma, which ultimately restrict bacterial growth.
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            Disseminated tuberculosis in interferon gamma gene-disrupted mice

            The expression of protective immunity to Mycobacterium tuberculosis in mice is mediated by T lymphocytes that secrete cytokines. These molecules then mediate a variety of roles, including the activation of parasitized host macrophages, and the recruitment of other mononuclear phagocytes to the site of the infection in order to initiate granuloma formation. Among these cytokines, interferon gamma (IFN-gamma) is believed to play a key role is these events. In confirmation of this hypothesis, we show in this study that mice in which the IFN-gamma gene has been disrupted were unable to contain or control a normally sublethal dose of M. tuberculosis, delivered either intravenously or aerogenically. In such mice, a progressive and widespread tissue destruction and necrosis, associated with very high numbers of acid- fast bacilli, was observed. In contrast, despite the lack of protective immunity, some DTH-like reactivity could still be elicited. These data, therefore, indicate that although IFN-gamma may not be needed for DTH expression, it plays a pivotal and essential role in protective cellular immunity to tuberculosis infection.
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              Requirement of Interleukin 17 Receptor Signaling for Lung Cxc Chemokine and Granulocyte Colony-Stimulating Factor Expression, Neutrophil Recruitment, and Host Defense

              Bacterial pneumonia is an increasing complication of HIV infection and inversely correlates with the CD4+ lymphocyte count. Interleukin (IL)-17 is a cytokine produced principally by CD4+ T cells, which induces granulopoiesis via granulocyte colony-stimulating factor (G-CSF) production and induces CXC chemokines. We hypothesized that IL-17 receptor (IL-17R) signaling is critical for G-CSF and CXC chemokine production and lung host defenses. To test this, we used a model of Klebsiella pneumoniae lung infection in mice genetically deficient in IL-17R or in mice overexpressing a soluble IL-17R. IL-17R–deficient mice were exquisitely sensitive to intranasal K. pneumoniae with 100% mortality after 48 h compared with only 40% mortality in controls. IL-17R knockout (KO) mice displayed a significant delay in neutrophil recruitment into the alveolar space, and had greater dissemination of K. pneumoniae compared with control mice. This defect was associated with a significant reduction in steady-state levels of G-CSF and macrophage inflammatory protein (MIP)-2 mRNA and protein in the lung in response to the K. pneumoniae challenge in IL-17R KO mice. Thus, IL-17R signaling is critical for optimal production of G-CSF and MIP-2 and local control of pulmonary K. pneumoniae infection. These data support impaired IL-17R signaling as a potential mechanism by which deficiency of CD4 lymphocytes predisposes to bacterial pneumonia.
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                Author and article information

                Journal
                J Exp Med
                J. Exp. Med
                jem
                The Journal of Experimental Medicine
                The Rockefeller University Press
                0022-1007
                1540-9538
                24 October 2011
                : 208
                : 11
                : 2251-2262
                Affiliations
                Division of Rheumatology, Immunology, and Allergy, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115
                Author notes
                CORRESPONDENCE Samuel M. Behar: sbehar@ 123456rics.bwh.harvard.edu
                Article
                20110919
                10.1084/jem.20110919
                3201199
                21967766
                f1a6b6f3-020c-4895-9027-039604749b25
                © 2011 Nandi and Behar

                This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

                History
                : 6 May 2011
                : 31 August 2011
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                Medicine
                Medicine

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