title: CD34+ hemopoietic progenitor cells are potent effectors of allergic inflammation.
abstract: BACKGROUND
  In steady state, hemopoietic progenitors constantly egress from the bone marrow (BM) into the blood and circulate through the peripheral tissues. In allergic diseases, the BM releases increased numbers of CD34(+) progenitor cells that migrate to the site of allergic inflammation, where they differentiate into tissue-dwelling and classic effector cells of allergy, such as mast cells, eosinophils, and basophils.
  
  
  OBJECTIVE
  To examine whether peripheral blood CD34(+) cells in addition to being progenitors may also directly function as inflammatory effector cells.
  
  
  METHODS
  Highly purified neonatal or adult blood CD34(+) cells were examined for the expression of thymic stromal lymphopoietin (TSLP) and IL-33 receptors and for their response to these cytokines as well as to supernatants of primary small airway epithelial cells and nasal explants from rhinosinusitis and control subjects. Sputum of patients with asthma was examined before and after allergen inhalation for the presence of IL-5 and IL-13-containing CD34(+) cells.
  
  
  RESULTS
  Circulating CD34(+) cells expressed receptors for TSLP and IL-33 and responded to these cytokines by rapidly releasing high levels of proinflammatory T(H)2-like cytokines and chemokines. These cells were activated in a TSLP-dependent manner by the supernatant fluids from activated primary human small airway epithelial cells and from nasal explants of patients with chronic rhinosinusitis. Moreover, activated CD34(+) cells containing IL-5 and IL-13 could be detected in the sputum of individuals with allergic asthma, with numbers increasing in response to specific allergen inhalation challenge.
  
  
  CONCLUSIONS
  Blood CD34(+) cells, in addition to being progenitors, may act as proinflammatory effector cells by themselves and directly contribute to the allergic inflammation.
authors.affiliation: Laboratory on Allergy, Centre Recherche Centre Hospitalier Universite Montreal (CRCHUM), Notre-Dame Hospital, Montreal, Quebec, Canada.
authors.forename: Zoulfia
authors.initials: Z
authors.lastname: Allakhverdi
authors.forename: Michael R
authors.initials: MR
authors.lastname: Comeau
authors.forename: Dirk E
authors.initials: DE
authors.lastname: Smith
authors.forename: Dean
authors.initials: D
authors.lastname: Toy
authors.forename: Leandra Mfuna
authors.initials: LM
authors.lastname: Endam
authors.forename: Martin
authors.initials: M
authors.lastname: Desrosiers
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Liu
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Howie
authors.forename: Judah A
authors.initials: JA
authors.lastname: Denburg
authors.forename: Gail M
authors.initials: GM
authors.lastname: Gauvreau
authors.forename: Guy
authors.initials: G
authors.lastname: Delespesse
mesh_terms: D000485:Allergens / Q000276:immunology / Q000378:metabolism; D018952:Antigens, CD34 / Q000276:immunology* / Q000378:metabolism; D001249:Asthma / Q000276:immunology* / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000276:immunology* / Q000378:metabolism; D000067596:Interleukin-33; D007378:Interleukins / Q000276:immunology; D018121:Receptors, Cytokine / Q000276:immunology / Q000378:metabolism; D013183:Sputum / Q000276:immunology / Q000378:metabolism; D000094632:Thymic Stromal Lymphopoietin
chemical_list: D000485:Allergens; D018952:Antigens, CD34; C498762:CRLF2 protein, human; D016207:Cytokines; C506536:IL33 protein, human; D000067596:Interleukin-33; D007378:Interleukins; D018121:Receptors, Cytokine; D000094632:Thymic Stromal Lymphopoietin