Аннотация:Abstract We previously demonstrated that m RNA for the pro‐inflammatory cytokine interleukin 20 ( IL ‐20) is expressed in suprapapillary keratinocytes of lesional psoriatic skin ( LS ). Here, we describe the distribution of IL ‐20 protein and the identity of the IL ‐20‐positive cells in LS . We found that the main part of IL ‐20 immunoreactivity is present in mononuclear cells of the dermal papillae, and that the IL ‐20‐positive cells located in the papillae were langerin+, CD 1a+, CD 4+ and CD 303+. These cells might be immature dendritic cell. In situ hybridization for IL ‐20 m RNA on non‐ LS , ex vivo stimulated with IL ‐1 β revealed a colocalization between IL ‐20 m RNA and the keratinocyte marker CK 14. No IL ‐20 m RNA was detected in the dermal mononuclear cells. Our results suggest that IL ‐20 is produced by keratinocytes, released into the epidermis and then possibly taken up by papillary mononuclear cells. Our study supports that IL ‐20 is involved in the pathogenesis of psoriasis.
