Complete inhibition of allergic airway inflammation and remodelling in quadruple IL-4/5/9/13−/− mice

BACKGROUND: T-helper type 2 (Th2)-derived cytokines such as IL-4, IL-5, IL-9 and IL-13 play an important role in the synthesis of IgE and in the promotion of allergic eosinophilic inflammation and airway wall remodelling. OBJECTIVE: We determined the importance of IL-13 alone, and of the four Th2 cytokines together, by studying mice in which either IL-13 alone or the Th2 cytokine cluster was genetically disrupted. METHODS: The knock-out mice and their BALB/c wild-type (wt) counterparts were sensitized and repeatedly exposed to ovalbumin (OVA) aerosol. RESULTS: Bronchial responsiveness measured as the concentration of acetylcholine aerosol needed to increase baseline lung resistance by 100% (PC100) was decreased in IL-13-/-, but increased in IL-4/5/9/13-/- mice. Chronic allergen exposure resulted in airway hyperresponsiveness (AHR) in wt mice but not in both genetically modified mice. After allergen exposure, eosinophil counts in bronchoalveolar lavage fluid and in airways mucosa, and goblet cell numbers were not increased in IL-4/5/9/13-/- mice, and were only attenuated in IL-13-/- mice. Airway smooth muscle (ASM) hyperplasia after allergen exposure was prevented in both IL-13-/- and IL-4/5/9/13-/- mice to an equal extent. Similarly, the rise in total or OVA-specific serum IgE levels was totally inhibited. CONCLUSION: IL-13 is mainly responsible for AHR, ASM hyperplasia and increases in IgE, while IL-4, -5 and -9 may contribute to goblet cell hyperplasia and eosinophilic inflammation induced by chronic allergen exposure in a murine model. Both redundancy or complementariness of Th2 cytokines can occur in vivo, according to specific aspects of the allergic response.     

Immunohistochemical detection of GM-CSF, IL-4 and IL-5 in a murine model of allergic bronchopulmonary aspergillosis

Background Granulocyte macrophage-colony stimulating factor (GM-CSF), interleukin-4 (IL-4) and IL-5 are important in tissue eosinophil accumulation and high IgE production in allergic inflammatory reaction. Objective We examine lung GM-CSF, IL-4 and IL-5 expression in a murine model of allergic bronchopulmonary aspergillosis (ABPA) characterized by eosinophil and lymphocyte lung infiltration and elevated serum IgE level. Methods C57BL/6 mice were intranasally treated three times a week for 1, 2 or 3 week(s) with Aspergillus fumigatus (Af) antigen or saline and were sacrificed on days 7, 14 and 21. Immunohistochemical analyses for GM-CSF, IL-4 and IL-5 were performed on lung sections. Results Af treatment induced a remarkable pulmonary eosinophil influx. Increased numbers of lung T lymphocytes and GM-CSF positive cells were observed on days 14 and 21. IL-4 and IL-5 positive cells were increased significantly only on day 14. Immunostained serial sections showed that most (≥98%) cytokine positive cells were CD3 positive. Few eosinophils (<2% of cytokine positive cells) were immunoreactive for GM-CSF and IL-5. Significant correlations were found between the number of GM-CSF and IL-5 positive cells, and the number of eosinophils in Af-treated lung (r = 0.62, P < 0.05 and r = 0.52, P < 0.05, respectively), and between the number of IL-4 positive cells and the serum total IgE level (r = 0.64, P<0.01). Conclusions Our data suggest a role for T lymphocyte GM-CSF, IL-4 and IL-5 in Af-induced mouse pulmonary eosinophilia and increased serum IgE production and further support the importance of T helper (TH) cells in the pathogenesis of ABPA.     

Bronchoalveolar lavage fluid concentrations of transforming growth factor (TGF)-β1, TGF-β2, interleukin (IL)-4 and IL-13 after segmental allergen challenge and their effects on α-smooth muscle actin and collagen III synthesis by primary human lung fibroblasts

RATIONALE: Asthmatic airway remodelling is characterized by myofibroblast hyperplasia and subbasement membrane collagen deposition. We hypothesized that cytokines and growth factors implicated in asthmatic airway remodelling are increased in bronchoalveolar lavage (BAL) fluid of asthmatics after segmental allergen challenge (SAC), and that these growth factors and cytokines increase alpha-smooth muscle actin (alpha-SMA) and collagen III synthesis by human lung fibroblasts (HLFs). METHODS: Transforming growth factor (TGF)-beta1, TGF-beta2, IL-4 and IL-13 levels were measured in BAL fluid from 10 asthmatics and 9 non-asthmatic controls at baseline and then 1 day, 1 week and 2 weeks after SAC. Confluent cultures of HLFs were stimulated by exogenous addition of TGF-beta1, TGF-beta2, IL-4 or IL-13 (concentration range 0.01-10 ng/mL) over 48 h. Collagen III was measured in culture supernates and alpha-SMA in cell lysates by Western blot. RESULTS: At baseline, there was no difference in BAL fluid concentrations of TGF-beta1, IL-4 and IL-13 between asthmatics and controls; however, non-asthmatics had higher concentrations of total TGF-beta2. In asthmatics, BAL fluid concentrations of all four factors increased significantly 1 day after SAC. TGF-beta1, TGF-beta2 and IL-13 concentrations returned to baseline by 1 week after SAC, but BAL fluid IL-4 concentration remained elevated for at least 2 weeks. TGF-beta1, TGF-beta2 and IL-4 significantly increased alpha-SMA in fibroblasts, but only IL-4 caused corresponding increases in collagen III synthesis. IL-13 had no direct effects on collagen III synthesis and alpha-SMA expression. CONCLUSIONS: Because IL-4 caused a dose-dependent increase in alpha-SMA and collagen III synthesis, it may be an important cytokine mediating asthmatic airway remodelling. TGF-beta1 and TGF-beta2 may also play a role in airway remodelling by stimulating phenotypic change of fibroblasts to myofibroblasts. Additionally, collagen III synthesis appears to be independent of myofibroblast phenotype and is apparently regulated by different growth factors and cytokines.