To clarify the role and regulation of eosinophils, we subjected several key eosinophil-related genetically engineered mice to a chronic model of allergic airway inflammation aiming to identify results that were independent of the genetic targeting strategy. In particular, mice with defects in eosinophil development (⌬dbl-GATA) and eosinophil recruitment [mice deficient in CCR3 (CCR3 knockout) and mice deficient in both eotaxin-1 and eotaxin-2 (eotaxin-1͞2 double knockout)] were subjected to Aspergillus fumigatus-induced allergic airway inflammation. Allergen-induced eosinophil recruitment into the airway was abolished by 98%, 94%, and 99% in eotaxin-1͞2 double knockout, CCR3 knockout, and ⌬dbl-GATA mice, respectively. Importantly, allergen-induced type II T helper lymphocyte cytokine production was impaired in the lungs of eosinophil-and CCR3-deficient mice. The absence of eosinophils correlated with reduction in allergen-induced mucus production. Notably, by using global transcript expression profile analysis, a large subset (29%) of allergen-induced genes was eosinophil-and CCR3-dependent; pathways downstream from eosinophils were identified, including in situ activation of coagulation in the lung. In summary, we present multiple lines of independent evidence that eosinophils via CCR3 have a central role in chronic allergic airway disease.allergy ͉ asthma ͉ chemokine ͉ cytokine

No abstract

IL-13 overexpression in the lung induces inflammatory and remodeling responses that are prominent features of asthma. Whereas most studies have concentrated on the development of IL-13-induced disease, far fewer studies have focused on the reversibility of IL-13-induced pathologies. This is particularly important because current asthma therapy appears to be poor at reversing lung remodeling. In this manuscript, we used an externally regulatable transgenic system that targets expression of IL-13 to the lung with the aim of characterizing the reversibility process. After 4 wk of doxycycline (dox) exposure, IL-13 expression resulted in mixed inflammatory cell infiltration, mucus cell metaplasia, lung fibrosis, and airspace enlargement (emphysema). After withdrawal of dox, IL-13 protein levels were profoundly reduced by 7 d and below baseline by 14 d. During this time frame, the level of lung eosinophils returned to near normal, whereas macrophages, lymphocytes, and neutrophils remained markedly elevated. IL-13-induced mucus cell metaplasia significantly decreased (91%) 3 wk after withdrawal of dox, showing strong correlation with reduced eosinophil levels. In contrast, IL-13-induced lung fibrosis did not significantly decline 4 wk after dox withdrawal. Importantly, IL-13-induced emphysema persisted, but modestly declined 4 wk after dox. Examination of transcript expression profiles identified a subset of genes that remained increased weeks after transgene expression was no longer detected. Notably, numerous IL-13-induced cytokines and enzymes were reversible (IL-6 and cathepsins), whereas others were sustained (CCL6 and chitinases) after IL-13 withdrawal, respectively. Thus, several hallmark features of IL-13-induced lung pathology persist and are dissociated from eosinophilia after IL-13 overexpression ceases.Keywords: asthma; cytokines; eosinophils; inflammation; lung Allergic asthma is characterized by chronic inflammation of the airways, airway wall remodeling, and a decline in respiratory function. In asthma, structural changes in the airway include mucus cell metaplasia, increased deposition of extracellular matrix proteins (e.g., collagen and proteoglycans), and hyperplasia of myofibroblasts and smooth muscle cells (1, 2). Airway remodeling and persistent inflammation contribute to disease pathogenesis of asthma. Animal studies have defined a critical effector role for IL-13 in many pathologic features of experimental asthma, including airway inflammation, tissue fibrosis, and mucus hypersecretion by goblet cells (3-5).The effector functions mediated by IL-13 include a diverse array of biological activities (6). IL-13-deficient animals, novel IL-13 antagonists, and transgenic overexpression modeling sys- tems have successfully defined a central role for IL-13 in some inflammatory diseases of the lung (6). In animal models, pulmonary overexpression of IL-13 results in inflammation, airway fibrosis, mucus metaplasia, airway hyperresponsiveness, and enhanced lung volumes and compliance (5, 7). The inflammatory ...