Interleukin-6 signal transduction and lymphocyte function

Interleukin-6 (IL-6) is a pleiotropic cytokine that acts on a wide variety of cell types. It has important regulatory functions in the immune system, is a mediator of the acute-phase response, and is involved in the regulatio n of differentiation, proliferation, and survival of target cells. A major signal transduction pathway for IL-6 involves activation of JAK kinases and the transcription factor Stat3. In addition, a great many of other signall ing pathways are induced. Stat3 has been shown to be a central player of IL -6 signalling in many systems whereas the functions of most other IL-6-acti vated pathways are not yet understood. In this review, we discuss the curre nt knowledge on IL-6 functions in the immune system, IL-6 signal transducti on, and its significance for lymphocyte function.