title: Resident CD8+ T cells suppress CD4+ T cell-dependent late allergic airway responses.
abstract: BACKGROUND
  The role of CD8+ T cells in the immune response to airway challenge with an allergen is poorly understood.
  
  
  OBJECTIVE
  The aim of this study was to test the hypothesis that resident naive CD8+ T cells modulate the magnitude of CD4+ T cell-dependent allergic airway responses.
  
  
  METHODS
  Cervical lymph node CD4+ T cells (2 x 10(6)) were harvested from ovalbumin (OVA)- or sham-sensitized rats and injected intraperitoneally into naive Brown Norway recipients. The recipients were treated with a CD8alpha mAb (OX-8) to deplete the resident CD8+ T cells (n = 12) or mouse ascites (n = 12). Two days after adoptive transfer, the recipient animals were OVA challenged, lung resistance was measured for 8 hours, and bronchoalveolar lavage (BAL) was performed.
  
  
  RESULTS
  After OVA challenge, primed CD4-transferred CD8-depleted rats had larger early airway responses and late airway responses compared with primed CD4-transferred CD8-nondepleted rats (early airway responses: 158.6% +/- 19.2% vs 115.7% +/- 5.9%, P < .05; late airway responses: 8.5% +/- 1.7% vs 4.4% +/- 0.9%, P < .05). BAL eosinophilia was also greater (4.67% +/- 0.45% vs 2.34 +/- 0.26%, P < .01). The cells in BAL fluid expressing IL-4 mRNA were not significantly changed by CD8 depletion, but IL-5 mRNA+ cells were higher in number, and IFN-gamma mRNA+ cells were fewer in the CD8-depleted group.
  
  
  CONCLUSIONS
  Resident CD8+ T cells downregulate the late allergic response and airway inflammation evoked by CD4+ T-cell transfers in Brown Norway rats. This downregulation does not require antigen priming.
authors.affiliation: Meakins Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Susumu
authors.initials: S
authors.lastname: Isogai
authors.forename: Sean
authors.initials: S
authors.lastname: Jedrzkiewicz
authors.forename: Rame
authors.initials: R
authors.lastname: Taha
authors.forename: Qutayba
authors.initials: Q
authors.lastname: Hamid
authors.forename: James G
authors.initials: JG
authors.lastname: Martin
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007371:Interferon-gamma / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D015848:Interleukin-5 / Q000276:immunology; D010047:Ovalbumin / Q000276:immunology; D012333:RNA, Messenger; D051381:Rats; D012130:Respiratory Hypersensitivity / Q000276:immunology*
chemical_list: D015848:Interleukin-5; D012333:RNA, Messenger; D015847:Interleukin-4; D007371:Interferon-gamma; D010047:Ovalbumin