title: In vivo regulation of replicative Legionella pneumophila lung infection by endogenous interleukin-12.
abstract: The in vivo role of endogenous interleukin 12 (IL-12) in modulating intrapulmonary growth of Legionella pneumophila was assessed by using a murine model of replicative L. pneumophila lung infection. Intratracheal inoculation of A/J mice with virulent bacteria (10(6) L. pneumophila cells per mouse) resulted in induction of IL-12, which preceded clearance of the bacteria from the lung. Inhibition of endogenous IL-12 activity, via administration of IL-12 neutralizing antiserum, resulted in enhanced intrapulmonary growth of the bacteria within 5 days postinfection (compared to untreated L. pneumophila-infected mice). Because IL-12 has previously been shown to modulate the expression of cytokines, including gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and IL-10, which regulate L. pneumophila growth, immunomodulatory effects of endogenous IL-12 on intrapulmonary levels of these cytokines during replicative L. pneumophila lung infection were subsequently assessed. Results of these experiments demonstrated that TNF-alpha activity was significantly lower, while protein levels of IFN-gamma and IL-10 in the lung were similar, in L. pneumophila-infected mice administered IL-12 antiserum, compared to similarly infected untreated mice. Together, these results demonstrate that IL-12 is critical for resolution of replicative L. pneumophila lung infection and suggest that regulation of intrapulmonary growth of L. pneumophila by endogenous IL-12 is mediated, at least in part, by TNF-alpha.
authors.affiliation: Unit for Laboratory Animal Medicine, The University of Michigan Medical School, Ann Arbor 48109-0614, USA. jbrie@umich.edu
authors.forename: J K
authors.initials: JK
authors.lastname: Brieland
authors.forename: D G
authors.initials: DG
authors.lastname: Remick
authors.forename: M L
authors.initials: ML
authors.lastname: LeGendre
authors.forename: N C
authors.initials: NC
authors.lastname: Engleberg
authors.forename: J C
authors.initials: JC
authors.lastname: Fantone
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D005260:Female; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D016753:Interleukin-10 / Q000276:immunology / Q000378:metabolism; D018664:Interleukin-12 / Q000276:immunology* / Q000378:metabolism*; D016952:Legionella pneumophila / Q000254:growth & development*; D007877:Legionnaires' Disease / Q000276:immunology*; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008815:Mice, Inbred Strains; D009500:Neutralization Tests; D013047:Specific Pathogen-Free Organisms; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism
chemical_list: D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D018664:Interleukin-12; D007371:Interferon-gamma