Interleukin-15 expression in cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome)

Background Cytokines are of potential importance in the pathogenesis of cut aneous T-cell mediated disorders, including cutaneous T-cell lymphoma (CTCL ). Objectives To compare interleukin (IL)-15 expression in certain inflammator y cutaneous diseases, with that in CTCL (mycosis fungoides and Sezary syndr ome). Methods IL-15 mRNA and protein expression were examined by in situ hybridiz ation and immunohistochemistry, respectively, on formalin-fixed, paraffin-e mbedded biopsies of normal human skin, atopic dermatitis, psoriasis, paraps oriasis and CTCL. Results Despite similar expression of IL-15 mRNA, we found differences in I L-15 protein expression between normal human skin, atopic dermatitis and ps oriasis on the one hand, and parapsoriasis and CTCL on the other. IL-15 pro tein 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 fungoi des and Sezary syndrome. Conclusions Induction of keratinocyte IL-15 expression appears to be a feat ure of CTCL. The factors stimulating such an expression remain unknown.