Epidermal cytokines.

The concept of the epidermis being a site for the initiation of immune responses has only been developed over the past decade. There is strong evidence that epidermal cells have immune functions. Accordingly the epidermis harbors dendritic cells having antigen presenting capacity and cells belonging to the T-cell family. Moreover, keratinocytes are capable of secreting various immunomodulating cytokines or secretory regulins. Cytokines are glycoproteins which are synthesized and secreted by various cells, bind to specific receptors and regulate activation, proliferation and differentiation of immune as well as non-immune cells. Keratinocytes upon injury i.e. mechanical irritation, ultraviolet irradiation, tumor promotors, synthesize and release interleukin-1 alpha, -1 beta, -6, -8, colony stimulating factors, tumor necrosis factors-alpha as well as growth (transforming growth factor beta) and suppressor (epidermal cell-contra-interleukin-1) factors. Since there is strong evidence in support of a network of interacting cytokines maintaining a proper balance which only partially has been discovered, so far no causative role of a single cytokine has been established in any disease. However, excessive or insufficient production of these mediators may contribute to certain disease states, particularly those of infectious and autoimmune origins. Thus, cytokines appear to be promising candidates for the treatment of infectious, autoimmune, immunodeficiency and malignant diseases. Future studies are necessary to clarify the therapeutic efficacy of the combined application of different cytokines and more investigations are also needed to elucidate the lymphokine cascade in vivo.