On the immunological theory of aging.

Aging is a complex phenomenon the cause of which is not fully understood, despite the plethora of theories proposed to explain it. As we age, changes in essentially all physiological functions, including immunity, are apparent. Immune responses decrease with aging, contributing to the increased incidence of different chronic diseases with an inflammatory component (sometimes referred to as 'inflamm-aging'). It is clear from many studies that human longevity may be influenced by these changes in the immune system, but how they proceed is not clearly determined. In this chapter, we will review the age-related changes in the immune response and assess the validity of the immune theory of aging (i.e. that these changes in immune response are the primary cause of aging). Many data in humans support the notion that age-associated immune dysfunction may at least in part explain the aging process. Explanatory power may be enhanced by combination with other theories such as the free radical theory. More longitudinal studies are needed to corroborate the immune theory of aging.