Background: Cytokines are of potential importance in the pathogenesis of cutaneous T-cell mediated disorders, including cutaneous T-cell lymphoma (CTCL).
Objectives: To compare interleukin (IL)-15 expression in certain inflammatory cutaneous diseases, with that in CTCL (mycosis fungoides and Sézary syndrome).
Methods: IL-15 mRNA and protein expression were examined by in situ hybridization and immunohistochemistry, respectively, on formalin-fixed, paraffin-embedded biopsies of normal human skin, atopic dermatitis, psoriasis, parapsoriasis and CTCL.
Results: Despite similar expression of IL-15 mRNA, we found differences in IL-15 protein expression between normal human skin, atopic dermatitis and psoriasis on the one hand, and parapsoriasis and CTCL on the other. IL-15 protein expression was not detected in normal human skin, atopic dermatitis or psoriasis, but was detected, mainly at low levels but in a few patients at higher levels, in epidermal keratinocytes in parapsoriasis, mycosis fungoides and Sézary syndrome.
Conclusions: Induction of keratinocyte IL-15 expression appears to be a feature of CTCL. The factors stimulating such an expression remain unknown.