title: FMS-like tyrosine kinase 3 ligand aggravates the lung inflammatory response to Streptococcus pneumoniae infection in mice: role of dendritic cells.
abstract: Pretreatment of mice with the hemopoietic growth factor, FMS-like tyrosine kinase 3 ligand (Flt3L), has been shown to increase monocyte-derived myeloid dendritic cells (DC) in lung parenchymal tissue, with possible implications for protective immunity to lung bacterial infections. However, whether Flt3L treatment improves lung innate immunity of mice to challenge with Streptococcus pneumoniae has not been investigated previously. Mice pretreated with Flt3L exhibited a peripheral monocytosis and a strongly expanded lung myeloid DC pool, but responded with a similar proinflammatory cytokine release (TNF-alpha, IL-6, keratinocyte derived cytokine, MIP-2, CCL2) and neutrophilic alveolitis upon infection with S. pneumoniae as did control mice with a normal lung DC pool. Unexpectedly, however, Flt3L-pretreated mice, but not control mice, infected with S. pneumoniae developed vasculitis and increased lung permeability by days 2-3 postinfection, and florid pneumonia accompanied by sustained increased bacterial loads by days 3-4 postinfection. This was associated with an overall increased mortality of approximately 35% by day 4 after pneumococcal challenge. Application of anti-CCR2 Ab MC21 to block inflammatory monocyte-dependent lung mononuclear phagocyte mobilization significantly reduced the lung leakage, but not vasculitis in Flt3L-pretreated mice infected with S. pneumoniae, without affecting the intra-alveolar cytokine liberation or the concomitantly developing neutrophilic alveolitis. Together, the data demonstrate that previous Flt3L-induced lung DC accumulation is not protective in lung innate immunity to challenge with S. pneumoniae, and support the concept that CCR2-dependent mononuclear phagocyte as opposed to neutrophil recruitment contributes to increased lung leakage in Flt3L-pretreated mice challenged with S. pneumoniae.
authors: Department of Pulmonary Medicine, Laboratory for Experimental Lung Research, Hannover School of Medicine, Hannover 30625, Germany.
authors: Christine
authors: C
authors: Winter
authors: Katharina
authors: K
authors: Taut
authors: Florian
authors: F
authors: Länger
authors: Matthias
authors: M
authors: Mack
authors: David E
authors: DE
authors: Briles
authors: James C
authors: JC
authors: Paton
authors: Regina
authors: R
authors: Maus
authors: Mrigank
authors: M
authors: Srivastava
authors: Tobias
authors: T
authors: Welte
authors: Ulrich A
authors: UA
authors: Maus
mesh_terms: D000818:Animals; D002634:Chemotaxis, Leukocyte; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects* / Q000276:immunology; D008168:Lung / Q000276:immunology* / Q000382:microbiology; D008565:Membrane Proteins / Q000633:toxicity*; D051379:Mice; D008807:Mice, Inbred BALB C; D009000:Monocytes / Q000276:immunology; D022423:Myeloid Cells / Q000276:immunology; D010539:Permeability; D011008:Pneumococcal Infections / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control; D011018:Pneumonia, Pneumococcal / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control; D054390:Receptors, CCR2 / Q000037:antagonists & inhibitors; D013296:Streptococcus pneumoniae
chemical_list: D016207:Cytokines; D008565:Membrane Proteins; D054390:Receptors, CCR2; C084881:flt3 ligand protein