A Murine Model of Toluene Diisocyanate-induced Contact Hypersensitivity

Background: Toluene diisocyanate (TDI) can cause contact allergy and occupational asthma, but the mechanism underlying sensitization to this chemical compound remains controversal. Also the correlation of mast cell with contact hypersensitivity (CHS) and the role of mast cell in the TDI-induced CHS is unknown. This issue was investigated by administrating TDI on the skin of genetically mast cell-deficient WBB6F1/$J-Kit^{W}/Kit^{W-v}$ ($W/W^{V}$) and congenic normal WBB6F1/J-Kit+/+ (+/+) mice. Methods: To development of animal model of TDI-induced CHS and to investigate the correlation of mast cell with CHS and the role of mast cell in the TDI-induced CHS, $W/W^V$ and +/+ mice were sensitized with TDI on the back skin at day 1 and day 8, and then challenged with 1% TDI on the ear at day 15. At 1, 2, 4, 8, and 24 hours after 1% TDI challenge, the ear thicknesses were measured. It was investigated the histologic changes of dermis in the ear of $W/W^V$ and +/+ mice at 24 hours after 1% TDI challenge. Results: TDI induced a significant ear swelling response in $W/W^V$ and +/+ mice. TDI induced the significant infiltrations of polymorphonuclear leukocytes and eosinophils in $W/W^V$ and +/+ mice, but not of mast cells in normal mice. And TDI increased a characteristic extent of mast cell degranulation in normal mice. There were no significant differences in the ear swelling and the infiltrations of polymorphonuclear leukocytes and eosinophils of normal versus $W/W^V$ mice, either at baseline or after TDI-induced CHS. Conclusion: From the above results, TDI can be used as a murine CHS model, and the mast cells may not be essential in TDI-induced CHS.