Legionella pneumophila down-regulates MHC class I expression of human monocytic host cells and thereby inhibits T cell activation |
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Authors: | B Neumeister M Faigle D Spitznagel A Mainka A Ograbek H Wieland N Mannowetz H -G Rammensee |
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Institution: | (1) Abteilung Transfusionsmedizin, AG Infektionsbiologie, Universitätsklinikum Tübingen, 72076 Tübingen, Germany;(2) Interfakultäres Institut für Zellbiologie, Abt. Immunologie, Universität Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany |
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Abstract: | Legionella (L.) pneumophila, the causative agent of Legionnaires disease, is an intracellular pathogen of alveolar macrophages that resides in a compartment displaying features of endoplasmatic reticulum (ER). In this study, we show that intracellular multiplication of L. pneumophila results in a remarkable decrease in MHC class I expression by the infected monocytes. During intracellular multiplication, L. pneumophila absorbs ER-resident chaperons such as calnexin and BiP, molecules that are required for the correct formation of the MHC class I complex. Due to reduced MHC class I expression, stimulation of allogeneic blood mononuclear cells was severely inhibited by infected host cells but cytotoxicity of autologous natural killer cells against Legionella-infected monocytes was not enhanced. Thus, reduced expression of MHC class I in infected monocytes may resemble a new immune escape mechanism induced by L. pneumophila.Received 22 November 2004; received after revision 27 December 2004; accepted 5 January 2005 |
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Keywords: | Legionella MHC class I antigens macrophages natural killer cells antigen presentation |
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