title: Migration of toxoplasma gondii-infected dendritic cells across human retinal vascular endothelium.
abstract: OBJECTIVE
  Toxoplasma gondii, the parasite responsible for ocular toxoplasmosis, accesses the retina from the bloodstream. We investigated the dendritic cell as a potential taxi for T. gondii tachyzoites moving across the human retinal endothelium, and examined the participation of adhesion molecules and chemokines in this process.
  
  
  METHODS
  CD14-positive monocytes were isolated from human peripheral blood by antibody-mediated cell enrichment, and cultured in granulocyte-macrophage colony-stimulating factor and interleukin-4 to generate dendritic cells. Transmigration assays were performed over 18 hours in transwells seeded with human retinal endothelial cells and using dendritic cells exposed to laboratory or natural strains of T. gondii tachyzoites. Parasites were tagged with yellow fluorescent protein to verify infection. In some experiments, endothelial monolayers were preincubated with antibody directed against adhesion molecules, or chemokine was added to lower chambers of transwells.
  
  
  RESULTS
  Human monocyte-derived dendritic cell preparations infected with laboratory or natural strain T. gondii tachyzoites transmigrated in larger numbers across simulated human retinal endothelium than uninfected dendritic cells (P ≤ 0.0004 in 5 of 6 experiments). Antibody blockade of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and activated leukocyte cell adhesion molecule (ALCAM) inhibited transmigration (P ≤ 0.007), and CCL21 or CXCL10 increased transmigration (P ≤ 0.031).
  
  
  CONCLUSIONS
  Transmigration of human dendritic cells across retinal endothelium is increased following infection with T. gondii. Movement may be impacted by locally produced chemokines and is mediated in part by ICAM-1, VCAM-1, and ALCAM. These findings have implications for development of novel therapeutics aimed at preventing retinal infection by T. gondii.
authors.affiliation: Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA.
authors.forename: João M
authors.initials: JM
authors.lastname: Furtado
authors.forename: Arpita S
authors.initials: AS
authors.lastname: Bharadwaj
authors.forename: Liam M
authors.initials: LM
authors.lastname: Ashander
authors.forename: Antoinette
authors.initials: A
authors.lastname: Olivas
authors.forename: Justine R
authors.initials: JR
authors.lastname: Smith
mesh_terms: D020410:Activated-Leukocyte Cell Adhesion Molecule / Q000378:metabolism; D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000378:metabolism / Q000469:parasitology / Q000473:pathology; D004730:Endothelium, Vascular / Q000378:metabolism / Q000469:parasitology* / Q000473:pathology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D012171:Retinal Vessels / Q000378:metabolism / Q000469:parasitology* / Q000473:pathology; D015398:Signal Transduction; D014122:Toxoplasma / Q000378:metabolism / Q000472:pathogenicity*; D014126:Toxoplasmosis, Ocular / Q000378:metabolism / Q000469:parasitology* / Q000473:pathology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D020410:Activated-Leukocyte Cell Adhesion Molecule; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1