The cytokines: physiological and pathophysiological aspects.

Publisher Summary This chapter discusses the physiological and pathophysiological aspects of cytokines. Despite the fact that many of the molecules are described on the basis of a single biological function, several molecules subsequently turned out to be pleiotropic with a wide range of actions and target cells. All cytokines act locally modulating the behavior of adjacent cells in a manner that is called “paracrine.” Many act on cells that secrete them (autocrine) or cells at distant sites (endocrine). An important action of some cytokines is the modulation of the function of other cytokines as well as the classical neurological and endocrine systems. The actions of an individual cytokine on a particular cell type may critically depend on the extracellular milieu of other mediators and on the modulation of intracellular signaling pathways. Another interesting aspect of many cytokines is the occurrence of redundancy that is more than one cytokine exhibiting the same biological activity. An extreme example of cytokine redundancy is tumor necrosis factor (TNF). The chapter also discusses the biochemistry, pathophysiology, and assays of cytokines in body fluid as well as its measurements in various diseases such as inflammation, infection, sepsis, endotoxemia, and bacterial shock.