title: Legionella pneumophila suppresses interleukin-12 production by macrophages.
abstract: In vitro infection of macrophages with Legionella pneumophila induced interleukin-1alpha (IL-1alpha), IL-10, monocyte chemotactic protein 1 (MCP-1), and MCP-3 but not IL-12. The lipopolysaccharide (LPS)-induced production of IL-12 was down-regulated by infection with virulent L. pneumophila, but other cytokines were not affected. In contrast, avirulent L. pneumophila or UV-killed, virulent L. pneumophila did not induce any suppression of IL-12. The IL-12 suppression occurred at the level of mRNA accumulation for IL-12 genes in response to LPS stimulation, but the infection induced a marked accumulation of mRNA for both MCP-1 and MCP-3, which are known to suppress IL-12 production in LPS-stimulated macrophages. However, pretreatment of macrophages with MCP-1 did not suppress LPS-induced IL-12 production at the concentrations induced by L. pneumophila infection. These results suggest that L. pneumophila selectively suppresses IL-12 production induced by LPS from macrophages in vitro by an MCP-independent mechanism.
authors.affiliation: Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
authors.forename: K
authors.initials: K
authors.lastname: Matsunaga
authors.forename: T W
authors.initials: TW
authors.lastname: Klein
authors.forename: C
authors.initials: C
authors.lastname: Newton
authors.forename: H
authors.initials: H
authors.lastname: Friedman
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D018932:Chemokine CCL2 / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D018664:Interleukin-12 / Q000378:metabolism*; D016952:Legionella pneumophila / Q000276:immunology* / Q000472:pathogenicity; D008070:Lipopolysaccharides / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000276:immunology*; D051379:Mice; D012333:RNA, Messenger / Q000096:biosynthesis
chemical_list: D018932:Chemokine CCL2; D016207:Cytokines; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018664:Interleukin-12