title: C5a contributes to intraocular inflammation by affecting retinal pigment epithelial cells and immune cells.
abstract: BACKGROUND
  The complement activation molecule C5a has been found in the eye and is implicated in the pathogenesis of ocular inflammatory diseases. In this study, the authors sought to investigate C5a's effects on human retinal pigment epithelial (RPE) cells and peripheral blood mononuclear cells (PBMCs), and on the interaction between RPE cells and PBMCs.
  
  
  METHODS
  Arising retinal pigment epithelia cell line-19 and PBMCs isolated from healthy donors were used in this study. Western blot, real-time PCR and cell surface receptor staining were used to detect C5a receptor expression. Real-time PCR was used to detect cytokine mRNA expression. A thiazolyl blue tetrazolium bromide assay was used to detect cell viability. Cells were stained with Annexin V and 7-aminoactinomycin D for an apoptosis assay. Cell proliferation was measured using a tritiated thymidine incorporation assay.
  
  
  RESULTS
  C5a receptors were present on RPE cells, and receptor expression was increased by pro-inflammatory cytokines. C5a suppressed RPE cells' production of transforming growth factor β2, an important immunosuppressive agent in the eye. In addition, the viability of RPE cells was decreased in the presence of C5a, and this effect was not due to apoptosis. C5a increased proliferation of PBMCs and upregulated their production of pro-inflammatory cytokines. Finally, C5a decreased RPE cells' ability to suppress immune cell proliferation.
  
  
  CONCLUSIONS
  The results provide a direct link between complement activation and intraocular inflammation. This line of information may help to understand the mechanism of the pathogenesis of intraocular inflammatory diseases. Moreover, the authors show that a close, reciprocal interaction between the innate immune system and the adaptive immune system may be involved in the development of such diseases.
authors.affiliation: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Mengjun
authors.initials: M
authors.lastname: Hu
authors.forename: Baoying
authors.initials: B
authors.lastname: Liu
authors.forename: Shayma
authors.initials: S
authors.lastname: Jawad
authors.forename: Diamond
authors.initials: D
authors.lastname: Ling
authors.forename: Megan
authors.initials: M
authors.lastname: Casady
authors.forename: Lai
authors.initials: L
authors.lastname: Wei
authors.forename: Robert B
authors.initials: RB
authors.lastname: Nussenblatt
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D004396:Coloring Agents; D015936:Complement C5a / Q000276:immunology*; D016207:Cytokines / Q000276:immunology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005123:Eye / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D005128:Eye Diseases / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression; D006801:Humans; D007155:Immunologic Factors / Q000276:immunology*; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D010857:Pigment Epithelium of Eye / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D044087:Receptor, Anaphylatoxin C5a / Q000276:immunology*; D013778:Tetrazolium Salts; D013844:Thiazoles; D053781:Transforming Growth Factor beta2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004396:Coloring Agents; D016207:Cytokines; D007155:Immunologic Factors; D012333:RNA, Messenger; D044087:Receptor, Anaphylatoxin C5a; D013778:Tetrazolium Salts; D013844:Thiazoles; D053781:Transforming Growth Factor beta2; D014409:Tumor Necrosis Factor-alpha; D015936:Complement C5a; C022616:thiazolyl blue