Peptides and cytokines.

In the last decade a number of proteinaceous inflammatory mediators have been structurally characterized. Two of these mediators, tumor necrosis factor alpha (TNF alpha) and Interleukin 1 alpha and beta (IL-1), have pleiotropic properties. Both cytokines are now known to be potent inducers of a number of cell-selective chemotactic cytokines, which belong to a novel superfamily of structurally related low-molecular-weight proteins. One of the most prominent members is termed "IL-8" and represents a neutrophil-selective attractant, whereas another one called "monocyte chemotactic protein 1 (MCP-1)" is a monocyte-selective chemotaxin. Other members seem to be selective chemotaxins for other leukocyte types and subsets. These chemotactic cytokines are produced by a variety of different cells under appropriate stimulation conditions. Large amounts of IL-8 have been detected in scales of psoriatic lesions and may be of importance in explaining predominant neutrophil infiltration in psoriatic lesions. Regulation of gene expression and/or release of these chemotactic cytokines may occur by IL-1 receptor antagonists or soluble TNF-alpha-receptors. So far, natural antagonists to these chemotactic cytokines have not been described; however, pharmacological inhibition of its gene expression and/or release is possible.