title: Activation of the lectin pathway of complement in experimental human keratitis with Pseudomonas aeruginosa.
abstract: OBJECTIVE
  Pseudomonas aeruginosa (P. aeruginosa) microbial keratitis (MK) is a sight-threatening disease. Previous animal studies have identified an important contribution of the complement system to the clearance of P. aeruginosa infection of the cornea. Mannose-binding lectin (MBL), a pattern recognition receptor of the lectin pathway of complement, has been implicated in the host defense against P. aeruginosa. However, studies addressing the role of the lectin pathway in P. aeruginosa MK are lacking. Hence, we sought to determine the activity of the lectin pathway in human MK caused by P. aeruginosa.
  
  
  METHODS
  Primary human corneal epithelial cells (HCECs) from cadaveric donors were exposed to two different P. aeruginosa strains. Gene expression of interleukin (IL)-6, IL-8, MBL, and other complement proteins was determined by reverse transcription-polymerase chain reaction (RT-PCR) and MBL synthesis by enzyme-linked immunosorbent assay and intracellular flow cytometry.
  
  
  RESULTS
  MBL gene expression was not detected in unchallenged HCECs. Exposure of HCECs to P. aeruginosa resulted in rapid induction of the transcriptional expression of MBL, IL-6, and IL-8. In addition, expression of several complement proteins of the classical and lectin pathways, but not the alternative pathway, were upregulated after 5 h of challenge, including MBL-associated serine protease 1. However, MBL protein secretion was not detectable 18 h after challenge with P. aeruginosa.
  
  
  CONCLUSIONS
  MK due to P. aeruginosa triggers activation of MBL and the lectin pathway of complement. However, the physiologic relevance of this finding is unclear, as corresponding MBL oligomer production was not observed.
authors.affiliation: Victorian Infectious Diseases Service, Royal Melbourne Hospital, Parkville VIC, Australia ; Department of Medicine, Royal Melbourne Hospital, University of Melbourne, VIC, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Osthoff
authors.affiliation: Centre for Eye Research Australia, East Melbourne VIC, Australia.
authors.forename: Karl D
authors.initials: KD
authors.lastname: Brown
authors.affiliation: Centre for Medicine Use and Safety, Monash University, Parkville VIC, Australia.
authors.forename: David C M
authors.initials: DC
authors.lastname: Kong
authors.affiliation: Centre for Eye Research Australia, East Melbourne VIC, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Daniell
authors.affiliation: Victorian Infectious Diseases Service, Royal Melbourne Hospital, Parkville VIC, Australia ; Department of Medicine, Royal Melbourne Hospital, University of Melbourne, VIC, Australia.
authors.forename: Damon P
authors.initials: DP
authors.lastname: Eisen
mesh_terms: D003167:Complement Activation / Q000235:genetics; D003165:Complement System Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D019573:Epithelium, Corneal / Q000473:pathology; D005786:Gene Expression Regulation; D056945:Hep G2 Cells; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007634:Keratitis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D037601:Mannose-Binding Lectin / Q000378:metabolism; D011552:Pseudomonas Infections / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000276:immunology*
chemical_list: D015850:Interleukin-6; D016209:Interleukin-8; D037601:Mannose-Binding Lectin; D003165:Complement System Proteins