Background  An important cellular aberration at sites of psoriatic inflammation is an increase in the number of dermal mast cells. Being multifactorial immune effector cells, it is believed that mast cells play an essential role in perpetuating the inflammatory process of psoriasis. However, factors responsible for the infiltration and accumulation of mast cells in psoriatic lesions are largely unknown. Recent studies have demonstrated that Interleukin‐8 (IL‐8) exerts strong chemotactic effects on mast cells in vitro. Overexpression of IL‐8 has also been reported in psoriatic lesions. In this study, we have found a correlation between the expression of IL‐8 and dermal mast cell density in lesional psoriatic skin as compared to nonlesional psoriatic skin.

Methods  Four‐mm punch biopsies were taken from 14 psoriatic patients and eight healthy volunteers. Using immunohistochemical techniques, 8 μm sections of lesional psoriatic, nonlesional psoriatic, and normal control samples were evaluated for dermal mast cell density and the density of IL‐8 expressing keratinocytes.

Results  It was found that dermal mast cell density in lesional psoriatic, nonlesional psoriatic, and normal skin was 105.4 ± 71.2, 42.3 ± 30.1, and 47.5 ± 32.5 mast cells/mm², respectively. IL‐8⁺ keratinocyte density in lesional psoriatic, non lesional psoriatic, and normal skin was 171.5 ± 67.1, 25.4 ± 14.9 and 20.6 ± 8.7 IL‐8⁺ Keratinocytes/mm², respectively.

Conclusions  The results of this study suggest that increased levels of IL‐8 in the keratinocytes of psoriatic plaques play a contributing role in the migration of mast cells to lesion sites.