Analyses of a mouse model of the dermatitis caused by 2,4,6-trinitro-1-chlorobenzene (TNCB)-repeated application

Background: The model of chronic dermatitis caused by repeated application of hapten is frequently used as a tool for assessment of the efficacy of a compound or the elucidation of chronic dermatitis. Objective: The purpose of this study is to provide more detailed analysis of the model of chronic dermatitis caused by repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB). Methods: BALB/c mice were sensitized with TNCB on day −7 to the ear, and then TNCB was repeatedly applied to the same ear three times per week, through days 0–21. Results: The repeated application of TNCB induced an increase of ear thickness, and a relatively steep increment of ear thickness from days 7 to 9 was observed. This increment reached almost a plateau at day 9. The peaks of ear swelling on days 7, 14 and 21 were approximately two times higher than that on day 0. Regarding cytokines in the ear, the highest production of IL-1β, 4, 6 and 18 were observed on day 7. The peak production of IL-1β, 4 and 6 on day 7 was found within 24 h after the challenge, while that of IL-18 was found at 0 h. The inflammatory cell infiltration into epidermis and dermis was observed and increased in day 7, then reached almost a plateau on day 9. Conclusion: The indices such as thickness, swelling and inflammatory cell infiltration in the lesional skin was increased and maintained by repeated application, however, the protein levels of some cytokines were not always consistent with the reactions.