Figure 5.

Senescent cell burden in the aging organism. Acute tissue damage causes a local, rapid increase in senescent cell burden, briefly disturbing the healthy balance (green area), followed by a rapid immune response aimed at clearing those cells. However, senescent cell burden increases with age, because of the “bystander” effect and incomplete senescent cell clearance caused by a deteriorating immune system. Further disturbance of this delicate senescent cell balance occurs as a result of degenerative processes and cancer.