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Toluene diisocyanate (TDI), a highly reactive industrial chemical, is one of the leading causes of occupation-related asthma in industrialized countries. The pathogenesis of TDI-induced asthma, however, remains not fully understood, in part due to lack of appropriate animal models. Twenty five female BALB/c mice (age: 8 weeks) were randomly divided into 5 groups: Ovabumin (OVA); OVA peptide amino acid residues No. 323–339 (Pep); TDI; alum and physiological saline. Mice were intraperitoneally injected with 25 μg OVA or pep absorbed on 300 μg alum, 300 μg alum or saline on days 0, 7 and 14. For the TDI group, mice were sensitized subcutaneously with 20 μl neat TDI on day 0; 20 μl of TDI in olive oil (1:10) on days 7 and 14; on days 21–23. Then each group was challenged intranasally with 20 μl of 1% OVA, 1% Pep, 1% TDI, 10% alum and saline respectively. On day 28, mice were killed under pentothal anesthesia. The results demonstrated that neutrophil-dominant inflammation with a few eosinophil infiltration occurred in the peri-bronchial and peri-vascular regions of the lungs. This was accompanied by hyperplasia/hypertrophy of cells lining the airways and mucus production as shown by HE staining. Positive immunohistochemical MBP staining in parenchyma was also shown. Th2 cytokine IL-4 and IgE production were significant increased 5 days after last challenge while IFN-γ level was below the detection limit. Conclusion: the clear elevation of IL-4 and IgE could allow to conclude a possible Th2-like dominated allergic response in TDI-exposed BALB/c mouse model. [ABSTRACT FROM AUTHOR]