Aging is defined as the progressive functional decline of tissue function accompanied by increasing mortality with advancing age. Many researchers proposed various theories of aging, however, precise molecular mechanism of organismal aging remains elusive. The presence of autoantibody and the concentration of various inflammatory cytokines are often correlated to age, even in healthy individuals who do not have autoimmune or infectious diseases. In addition, low grade chronic inflammation has been regarded as a background for many age-related human diseases. These findings suggest that chronic inflammation plays a causative role in organismal aging and that proper regulation of aged immune system may decelerate organismal aging.