Prolonged eosinophil production after allergen exposure in IFN-gammaR KO mice is IL-5 dependent.
Asthma is a T helper 2 (Th2)-driven inflammatory process characterized by eosinophilia. Prolonged airway eosinophilia is commonly observed in asthma exacerbations. Our aim was to evaluate whether eosinophilia in prolonged allergic inflammation is associated with a continuous supply of new eosinophils to the airways, and how this is regulated. Ovalbumin (OVA)-sensitized interferon-gamma receptor knockout mice (IFN-gammaR KO), known to maintain a long-lasting eosinophilia after allergen exposure, were compared to wild type (wt) controls. Animals were exposed to OVA or phosphate-buffered saline on three consecutive days, and bone marrow (BM), blood and bronchoalveolar lavage (BAL) samples were collected 24 h, 7 and 21 days later. Newly produced cells were labelled using bromodeoxyuridine (BrdU). Serum IL-5 was measured and its role was investigated by administration of a neutralizing anti-IL-5 antibody. In-vitro eosinophilopoiesis was examined in both groups by a colony-forming assay. Allergen challenge increased eosinophils in BM, blood and BAL, in both IFN-gammaR KO and wt mice, both 24 h and 7 days after the last allergen exposure. At 21 days after the last exposure, only IFN-gammaR KO mice maintained significantly increased eosinophil numbers. Approximately 50% of BAL granulocytes in IFN-gammaR KO were produced during the last 6 days. Interleukin (IL)-5 concentration was increased in IFN-gammaR KO mice, and anti-IL-5 reduced eosinophil numbers in all compartments. Increased numbers of eosinophil colonies were observed in IFN-gammaR KO mice after allergen exposure versus controls. In this model of a Th2-driven prolonged allergic eosinophilia, new eosinophils contribute to the extended inflammation in the airways by enhanced BM eosinophilopoiesis in an IL-5-dependent manner.
Zhao
L-L
LL
Lung Pharmacology Group, Department of Internal Medicine/Respiratory and Allergology, The Sahlgrenska Academy, Göteborg University, Gothenburg, Sweden.
Lötvall
J
J
Lindén
A
A
Tomaki
M
M
Sjöstrand
M
M
Bossios
A
A
D000485:Allergens / Q000009:adverse effects; D000818:Animals; D001853:Bone Marrow / Q000276:immunology; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D004804:Eosinophils / Q000276:immunology*; D007249:Inflammation / Q000276:immunology / Q000473:pathology; D015848:Interleukin-5 / Q000097:blood / Q000276:immunology*; D007958:Leukocyte Count; D051379:Mice; D018345:Mice, Knockout; D010047:Ovalbumin / Q000009:adverse effects; D017471:Receptors, Interferon / Q000172:deficiency / Q000235:genetics; D012130:Respiratory Hypersensitivity / Q000097:blood / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology; D000096743:Interferon gamma Receptor
D000485:Allergens; D015848:Interleukin-5; D010047:Ovalbumin; D017471:Receptors, Interferon; D000096743:Interferon gamma Receptor