Interleukin‐6: A Cytokine for Gerontolgists

Interleukin‐6 (IL‐6) is a multifunctional cytokine that presumably plays its major role as a mediator of several of the acute phase inflammatory responses. These include inflammatory cell and lymphocyte activation and hepatocellular stimulation of acute phase protein synthesis. IL‐6 expression is normally low, and serum levels are usually non‐detectable in the absence of inflammation. However, with advancing age, serum levels become detectable, and it is proposed that this reflects an age‐associated loss in the normal regulation of gene expression for this molecule. The cause of this is most likely multi‐factorial, but there is evidence that it relates to an age‐associated loss of T cell immunoregulatory functions as well as menopausal loss of estrogen. In any event, the “inappropriate” presence of IL‐6 results in many changes typical of chronic inflammation. There is also speculation that IL‐6 may contribute to the pathogenesis of several diseases of late‐life including lymphoma, osteoporosis, and Alzheimer's disease. In this review the biology of this important cytokine is presented and its relevance to gerontology is highlighted.