Interleukin-6 and aging: blood levels and mononuclear cell production increase with advancing age and in vitro production is modifiable by dietary restriction.

Interleukin-6 (IL-6) is a multifunctional cytokine that is proving to be a major contributor to the acute phase inflammatory response. IL-6 expression is normally low and serum levels are usually nondetectable in the absence of inflammation. With advancing age, however, 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. There is also speculation that IL-6 may contribute to the pathogenesis of several diseases that are common in late-life including lymphoma, osteoporosis, and Alzheimer's disease. In this report we demonstrate that plasma levels of IL-6 rise with advancing age in well-selected healthy elderly people and comparably in old rhesus monkeys. That this change reflects a primary aging process is suggested by our findings in C57BL/6 mice in which the age-associated increase in the in vitro synthesis of IL-6 is largely prevented by life span-extending dietary restriction.