TDI can induce respiratory allergy with Th2-dominated response in mice

Toluene diisocyanate (TDI), a highly reactive industrial chemical is one of the leading causes of occupation-related asthma in industrialized countries. The pathophysiology of TDI-induced asthma, however, remains poorly understood, in part due to a lack of appropriate animal models. In this Study, four models of TDI-sensitised mice were investigated. In model number 1, the mice were sensitised for 4 h/day on four consecutive days to 3 ppm inhaled TDI and challenged twice for 4 h each time with 0.3 ppm inhaled TDI. In model number 2, the sensitising condition was similar to that of model 1, but the challenge conditions involved an initial inhalation of 2 ppmTDI for 4 h and then tracheal instillation with 50 mu g/mouse albumin-TDI. In model number 3, the mice were sensitised first to 25% TDI (sc) and then three times for 4 h each time to I ppm inhaled TDI and challenged twice for 4 h each time with 0.1 ppm inhalated TDI. In model number 4, the mice were first sensitised to 1% TDI by skin application and then with 0.2% TDI by tracheal instillation and challenged tree times by tracheal instillation of 0.1% TDI. In model number 4, skin application followed by tracheal instillations of TDI led to local and systemic Th2-dominated immune responses that were characterized: (1) in the lung-associated lymph nodes by a decrease in Th1 cytokine (IFN-gamma) production associated with an increase in Th2 cytokine (IL-4, IL-5, IL-3) production; (2) in the lungs by an allergic inflammation throughout the conducting airways: goblet cell proliferation and eosinophil influx and; (3) in the serums by increased total and specific IgE levels, 17.5- and 3.5-fold higher than that of the controls. respectively. The conditions used for sensitisation in the other models, i.e. inhalation or subcutaneous administration plus inhalation, failed to induce a strong Th2 response like that observed in model number 4. The findings indicate that TDI can induce a Th2-dommated response in mice when administered by topical application plus tracheal instillation for sensitisation and by intratracheal instillation for challenge (model number 4). This mouse Th2 model of TDI-induced airway allergy can, in several aspects, mimic occupational TDI asthma in humans and may prove to be useful in determining the mechanistic basis behind this disease. (c) 2005 Elsevier Ireland Ltd. All rights reserved.