title: Inhibitory effects of endogenous and exogenous interferon-gamma on bronchial hyperresponsiveness, allergic inflammation and T-helper 2 cytokines in Brown-Norway rats.
abstract: Interferon-gamma (IFN-gamma) is an important cytokine involved in the regulation of allergen-induced immune responses. We examined the role of IFN-gamma in a Brown-Norway rat model of bronchial hyperresponsiveness (BHR) and airway eosinophilia, and its effects on the mRNA expression of T helper type 1 (Th1)/Th2 cytokine. Ovalbumin (OA)-sensitized animals were given either exogenous IFN-gamma (105 U/rat over 3 days, intraperitoneally) or anti-IFN-gamma blocking antibody (DB-1 0.3 mg/rat, intravenously) prior to exposure to OA aerosol and were studied 18-24 hr later. In sensitized animals, OA induced significant BHR, accumulation of eosinophils, T lymphocytes and neutrophils in bronchoalveolar lavage (BAL) fluid, and also increased eosinophils and CD8+ T cells in the airways. Exogenous IFN-gamma attenuated allergen-induced BHR (P<0.02, compared with sham-treated animals) together with a significant reduction in eosinophil and neutrophil numbers in BAL fluid (P<0. 005), and eosinophils and CD8+ T cells in airways (P<0.05). By contrast, anti-IFN-gamma antibody increased airway CD4+ T cells and BHR. Using reverse transcriptase-polymerase chain reaction, significant increases in Th2 [interleukin-4 (IL-4), IL-5 and IL-10], and IFN-gamma cytokine mRNA were found in the lungs of sensitized and OA-exposed animals, while exogenous IFN-gamma significantly suppressed IL-4, IL-5 and IL-10 mRNA expression, and anti-IFN-gamma antibody increased IL-4 and IL-5 mRNA expression. These results indicate that Th1 effects, such as those mediated by IFN-gamma, play a down-regulatory role to suppress the Th2 responses associated with allergen-induced BHR and eosinophilic inflammation.
authors.affiliation: Thoracic Medicine, Chang Gung Memorial Hospital, Keelung Branch, Taiwan.
authors.forename: T J
authors.initials: TJ
authors.lastname: Huang
authors.forename: P A
authors.initials: PA
authors.lastname: MacAry
authors.forename: T
authors.initials: T
authors.lastname: Wilke
authors.forename: D M
authors.initials: DM
authors.lastname: Kemeny
authors.forename: K F
authors.initials: KF
authors.lastname: Chung
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015139:Blotting, Southern; D001980:Bronchi / Q000276:immunology*; D016535:Bronchial Hyperreactivity / Q000276:immunology*; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D002452:Cell Count; D004804:Eosinophils; D007371:Interferon-gamma / Q000276:immunology / Q000494:pharmacology*; D016753:Interleukin-10 / Q000235:genetics; D015847:Interleukin-4 / Q000235:genetics; D015848:Interleukin-5 / Q000235:genetics; D007378:Interleukins / Q000235:genetics*; D008297:Male; D009504:Neutrophils; D010047:Ovalbumin; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011914:Rats, Inbred BN; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes; D018418:Th2 Cells / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015848:Interleukin-5; D007378:Interleukins; D012333:RNA, Messenger; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma; D010047:Ovalbumin