Legionella pneumophila suppresses interleukin-12 production by macrophages.
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.
Matsunaga
K
K
Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
Klein
T W
TW
Newton
C
C
Friedman
H
H
Yamamoto
Y
Y
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
D018932:Chemokine CCL2; D016207:Cytokines; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018664:Interleukin-12