In situ localization of interleukin-1 in normal and psoriatic skin.

Interleukin-1 (IL-1) is a family of polypeptides that mediates a wide range of inflammatory and immune responses. In human skin, unstimulated keratinocytes produce a large amount of such cytokines. Although the precise role of IL-1 in the skin is unknown, there is experimental evidence supporting involvement of IL-1 in the pathogenesis of inflammatory skin diseases. In this study, we investigated in situ localization of IL-1 alpha and IL-1 beta in normal and psoriatic skin. Using polyclonal antibodies and the avidin-biotin peroxidase complex, we demonstrated the presence of both IL-1 alpha and IL-1 beta in normal and psoriatic formalin-fixed paraffin-embedded tissues. In both cases, IL-1 alpha was more prominent. However, the distribution of IL-1 alpha differed between normal and psoriatic skin. In normal skin, IL-1 alpha distribution was predominantly intercellular, whereas IL-1 alpha distribution was predominantly within the cytoplasm in psoriatic skin. These studies confirm that IL-1 alpha is the predominant form of IL-1 in the skin and provide further support for the hypothesis that IL-1 participates in the pathogenesis of psoriasis.