Dithranol modulates the leukotriene B4-induced intraepidermal accumulation of polymorphonuclear leukocytes.

Dithranol, with and without the addition of salicylic acid, was applied daily on normal skin according to a short contact protocol as used in the treatment of psoriasis. Sellotape stripping and epicutaneous application of leukotriene B4 (LTB4) were carried out within these pretreated areas. The challenged skin was subsequently biopsied and the intraepidermal accumulation of polymorphonuclear leukocytes (PMN) was quantified using the marker enzyme elastase. Dithranol pretreatment yielded a significant reduction of the LTB4-induced accumulation of PMN, whereas the tape stripping-induced accumulation of PMN was not affected by dithranol pretreatment. The addition of salicylic acid did not significantly enhance the effect of dithranol.