title: Decrease in circulating plasmacytoid dendritic cells during short-term systemic normobaric hypoxia.
abstract: BACKGROUND
  During exposure to high altitude, the immune system is altered. During hypoxia, an increase in interleukin (IL)-6 and high sensitivity C-reactive protein (hs-CRP), and an increase in natural killer cells and decrease in T cells in blood was shown. However, the impact of hypoxia on dendritic cells has not been investigated yet.
  
  
  METHODS
  Twelve healthy volunteers were subjected to a transient normobaric hypoxia for 6·5 h simulating an oxygen concentration at 5500 m. During exposure to hypoxia, blood samples were collected and analysed by flow cytometrical cell sorting (FACS) for circulating myeloid (mDCs) and plasmacytoid (pDCs) DCs. Serum levels of IL-6 and tumour necrosis factor (TNF)-α were analysed. In a cell culture hypoxia chamber, blood samples were subjected to the same hypoxia and analysed regarding DCs.
  
  
  RESULTS
  Exposure to normobaric hypoxia induced a significant decrease in circulating pDCs about 45% (P = 0·001) but not of mDC compared to baseline normoxia. Furthermore, we observed a significant increase of TNF-α about 340% (P = 0·03) and of IL-6 about 286% (P = 0·002). In cell culture experiments exposure of blood to hypoxia led to no significant changes in DCs, so that a direct cytotoxic effect was excluded. During hypoxia, we observed a transient increase in stromal-derived factor 1 (SDF-1) which is important for pDC tissue recruitment.
  
  
  CONCLUSIONS
  We show a significant decrease in circulating pDCs during hypoxia in parallel to a pro-inflammatory response. Further studies are necessary to evaluate whether the decrease in circulating pDCs might be the result of an enhanced tissue recruitment.
authors: Internal Medicine II, Elisabeth Hospital Schmalkalden, Schmalkalden, Germany.
authors: Atilla
authors: A
authors: Yilmaz
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Josi
authors: J
authors: Ratka
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Ilonka
authors: I
authors: Rohm
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Rudin
authors: R
authors: Pistulli
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Bjorn
authors: B
authors: Goebel
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Yahya
authors: Y
authors: Asadi
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Alexander
authors: A
authors: Petri
authors: Department of Clinical Chemistry & Laboratory Medicine, University Hospital of Jena, Jena, Germany.
authors: Michael
authors: M
authors: Kiehntopf
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Hans R
authors: HR
authors: Figulla
authors: Clinic for Internal Medicine I, University Hospital of Jena, Jena, Germany.
authors: Christian
authors: C
authors: Jung
mesh_terms: D000328:Adult; D000531:Altitude; D001274:Atmospheric Pressure; D002452:Cell Count; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000276:immunology*; D015850:Interleukin-6 / Q000276:immunology*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D022423:Myeloid Cells / Q000166:cytology / Q000276:immunology; D010092:Oximetry; D056152:Respiratory Rate; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; D019344:Lactic Acid
keywords: Dendritic cells; immune system; normobaric hypoxia