Cytokines in the liver

Cytokines comprise a group of small proteins released from cells in order t o influence the function of other cells. By binding to highly specific cell -surface receptors, they trigger a vast array of intracellular signalling c ascades. Cytokines have been described as interleukins, growth factors, int erferons and chemokines, Unlike hormones, which act in a similar way, cytok ines are produced by many different types of cell and act on many other typ es. Most of them are produced only after certain stimuli. The most intense field of cytokine activity is without doubt host defence. The liver resembles a central organ of cytokine activity due to the fact th at it hosts hepatocytes, which are highly susceptible to the activity of cy tokines in a variety of physiological and pathophysiological processes, Mor eover, the non-parenchymal cells of the liver, in particular Kupffer cells (KCs), the resident tissue macrophages of the liver, are able to synthesize a variety of cytokines that may act systemically on any other organ of the body, or in a paracrine manner on hepatocytes and other nonparenchymal liv er cells. A classic example of how cytokines act can be observed during the acute phase reaction discussed in this article, The role of cytokines in l iver development, acute liver injury, liver regeneration, liver fibrosis an d liver metastasis is also discussed. (C) 2001 Lippincott Williams & Wilkin s.