The role of cytokines in the psoriatic inflammation

Psoriasis represents an inflammatory skin disorder which is characterized by a marked hyperproliferation of keratinocytes in association with vascular expansion, fibroblast activation, leukocyte infiltration, alterations of eicosanoid metabolism and of cytokine production. However, it is unclear at present whether these changes may be a cause or a result of the significantly increased keratinocyte turnover. More than one mechanism is involved in triggering active psoriasis, particularly a genetic predisposition and environmental factors affecting the immune system. Most of the therapeutic regimes used for the treatment of psoriasis are immunosuppressive. Therefore, it is tempting to speculate that a specific defect of the immune system represents an important pathogenic principle in psoriasis. There are several lines of evidence that changes in cytokine production by keratinocytes and immunocompetent cells in the skin of the patients (particularly of interleukin-6 and TGF-alpha) may play an important role in the propagation of the inflammatory response in psoriasis. Further studies are required to reveal the role of a local T-cell activation as a basic mechanism for initiation and maintenance of the psoriatic inflammatory response. Accordingly, parameters, such as the evaluation of cytokine production in vitro and in vivo, as well as the measurement of cellular activation products, may be useful tools for diagnosis and monitoring of psoriasis.