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The immune system in experimental Pseudomonas keratitis: model and early effects. to infection has both positive, protective effects as well as negative, destructive effects on tissues, it is less well appreciated that interventions that modulate inflammation can have different effects on outcomes in different tissues. The eye is a notable tissue to evaluate such effects, not only due to its basal immune-privileged status but also because inflammatory-mediated damage to tissues like the cornea that result in clearance of infecting microbes also leads to significant damage (35) that severely compromises eyesight, whereas comparable scarring in other tissues is often of little consequence. is a leading cause of bacterial eye infections in humans (2, 13, 29, 33), and interventions are needed that promote bacterial clearance while limiting tissue-associated pathology due to a rapid and extensive influx of neutrophils. Neutrophil recruitment to infected tissues, particularly tissues infected with extracellular bacteria and fungi (7, 25), is often highly dependent on the proinflammatory cytokine interleukin-17 (IL-17) produced by helper T cells called Th17 cells (11, 21), although the importance of IL-17 varies by pathogen, tissue, and type of infection. For example, antibody-mediated depletion of IL-17 or deficiency of the IL-17 receptor (IL-17R) had no effect on Rabbit Polyclonal to CRABP2 the course of lung infection, but these interventions did diminish the protective efficacy of a live-attenuated vaccine against lethal pneumonia (27). Intercellular adhesion molecule 1 (ICAM-1), a receptor for the neutrophil 2-integrins LFA-1 and Mac-1, is expressed on epithelial and endothelial cells during infection and facilitates neutrophil recruitment to infected tissues, including the eye (17), but the relative contributions of IL-17 and ICAM-1 to neutrophil influx and host defense during bacterial keratitis are unknown. Neutralization of IL-17 activity in the cornea during bacterial keratitis could have potential therapeutic use due to the need to limit neutrophil-associated pathology in this setting, but decreasing neutrophil influx might also interfere with S55746 hydrochloride bacterial clearance. In this study, we show that the absence of the IL-17 receptor is associated with diminished ICAM-1 expression after corneal infection. We also demonstrate that absence of the IL-17 receptor or ICAM-1 or antibody-mediated neutralization of IL-17 leads to lower corneal pathology S55746 hydrochloride scores, diminished neutrophil infiltration, and decreased bacterial levels. MATERIALS AND METHODS Bacterial strains and mice. We utilized clinical isolates of originally obtained from infected corneal ulcers: strains 6294 and 6354 (both are ExoS-producing invasive strains of serogroup O6), 6077 and 6206 (both are ExoU-producing cytotoxic strains of serogroup O11) (39), and the laboratory strain PAO1 as well as its cytotoxic variant, denoted S55746 hydrochloride ExoU+ PAO1, which contains a plasmid with the genes for the type III secretion toxin ExoU and its chaperone, SpcU (3). C57BL/6 mice were purchased from Taconic for experiments that included IL-17R knockout (KO) mice and from Jackson Laboratory for experiments that included ICAM-1 KO mice. IL-17R KO mice were provided by Amgen, and ICAM-1 KO mice (full gene deletion) were provided by Daniel Bullard of the University of Alabama at Birmingham (5). Animal experiments complied with institutional and federal guidelines regarding the use of animals in research. Murine corneal infection model. Corneal infection was initiated on scratch-injured eyes of S55746 hydrochloride anesthetized S55746 hydrochloride mice, as previously described (26, 38). Bacteria were grown overnight at 37C on Trypticase soy agar (TSA) and resuspended in 1% proteose.