Inflammatory and immune reactions associated with stratum corneum and neutrophils in sterile pustular dermatoses

In this review we present our own experimental findings as well as those fr om the literature related to the pathomechanisms for the inflammatory chang es in psoriasis and its related diseases. A growing body of evidence has in dicated that T cell-mediated immunity plays an important role in triggering and maintenance of psoriatic lesions. It has been revealed that lymphokine s produced by activated T cells in psoriatic lesions have a strong influenc e on the proliferation of the epidermis. Characteristic neutrophil accumula tion under the stratum corneum can be observed in the highly inflamed areas of psoriatic lesions. These neutrophils are chemotactically attracted and activated there by synergistic action of chemokines, IL-8 and Gro-alpha rel eased by stimulated keratinocytes, and particularly by C5a/C5a des arg prod uced via the alternative complement pathway activation. We demonstrated tha t the infiltrating neutrophils adhere to iC3b-opsonized corneocytes to prod uce active oxygen and probably lysosomal enzymes. From a close relationship observed between neutrophil accumulation and high mitotic ratio of the les ional epidermis, we think that these stimulated neutrophils influence the g rowth and differentiation of epidermal keratinocytes. Aberrant expression o f HLA-DR on neutrophils suggests their activation of infiltrating T cells i n the presence of bacterial superantigen. These T cells in turn influence t he transepidermal neutrophil migration through the effect of their cytokine s on the keratinocyte production of proinflammatory mediators including IL- 8 and C3. In this review we discuss the pivotal roles played by stratum cor neum and neutrophils in several skin diseases, where neutrophils accumulate beneath the stratum corneum in a sterile condition. (C) 2000 Tohoku Univer sity Medical Press.