Affiliation: Institute for Infection Medicine, Christian Albrechts University of Kiel, Brunswiker Str. 4, 24105 Kiel, Germany.
Interleukin-26 (IL-26) belongs to the family of cellular cytokines which share sequence homology with IL-10, however, without functional conservation. The il-26 gene is situated on the human chromosome 12q15 in close neighbourhood to the genes for the related T-cellular cytokines interferon-γ (IFN-γ) and IL-22. il-26 was discovered due to its overexpression in T cells after growth transformation with herpesvirus saimiri. IL-26 is produced by activated T cells, forms homodimers, and acts on epithelial target cells such as colon carcinoma cells or keratinocytes. Presumably due to its positive net charge, IL-26 adheres to glycosaminoglycans on cell surfaces. Stimulation with IL-26 results in the phosphorylation and activation of the transcription factors STAT1 and STAT3 and in the induction of CD54 surface expression and secretion of cytokines such as IL-8 and IL-10. These effects are mediated by an IL-26-specific receptor complex consisting of IL-20R1 and IL-10R2. Thus, IL-26 appears to be a rather proinflammatory and cell-surface associated cytokine linking local T-cell activation with epithelial functions.