title: Increased HLA-DR expression after exposure of human monocytic cells to air particulates.
abstract: BACKGROUND
  The expression of HLA-DR on the cell membrane of antigen-presenting cells is of major importance for the induction of an allergic response in the airways. Environmental particulates are thought to play an important role in inducing or enhancing allergic sensitization, possibly by increasing the expression of HLA-DR on the cell membrane of antigen-presenting cells. In addition, these particulates may synergize with common sensitizing agents in inducing or enhancing HLA-DR and thus antigen presentation.
  
  
  OBJECTIVE
  In this study, we investigated the potential of three particle types, namely carbon black, diesel exhaust particles and urban air particulates (0.1-1000 ng/cm(2)), to induce the expression of HLA-DR on differentiated THP-1 cells, taken as a model for alveolar macrophages. We also assessed the "adjuvant" potential of the particles on interferon (IFN)-gamma, a known enhancer of HLA-DR.
  
  
  RESULTS
  By themselves, the particles (0.1-1000 ng/cm(2)) were not able to induce HLA-DR on the THP-1 cells after an incubation of 48 h. However, even at very low concentrations, carbon black (from 1 ng/cm(2) on) and diesel exhaust particles (from 0.1 ng/cm(2) on), interacted with IFN-gamma (100 U/mL) to enhance HLA-DR expression (up to 2.5-fold increase).
  
  
  CONCLUSIONS
  This finding may reflect in vitro one of the mechanisms by which pollutant particles exert an "adjuvant" activity and may partially explain how exposure to particles can be related to the enhancement of allergic sensitization.
authors.affiliation: Vlaamse Instelling voor Technologisch Onderzoek (Vito), Environmental Toxicology, Boeretang 200, B-2400 Mol, Belgium. ann.donportocarero@vito.be
authors.forename: Ann
authors.initials: A
authors.lastname: Don Porto Carero
authors.forename: P H M
authors.initials: PH
authors.lastname: Hoet
authors.forename: B
authors.initials: B
authors.lastname: Nemery
authors.forename: G
authors.initials: G
authors.lastname: Schoeters
mesh_terms: D000397:Air Pollution; D002244:Carbon / Q000494:pharmacology; D002460:Cell Line; D002947:Cities; D006684:HLA-DR Antigens / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*; D001335:Vehicle Emissions
chemical_list: D006684:HLA-DR Antigens; D001335:Vehicle Emissions; D002244:Carbon; D007371:Interferon-gamma