Senescent cells accumulate with age, a way to suppress cancer risk by shutting down damaged cells, but one that leads to all sorts of other biochemical damage. Here, researchers theorize that senescent cells lead to issues with the immune system and thus the age-related increase in risk of autoimmune disease. Compare this with the theory that issues with the immune system lead to an inability to destroy senescent cells, and thus their accumulation. As you can see many very fundamental and important issues of cause and effect in the aging body are still up for debate. "If the hypothesis is correct, the control of the formation, accumulation and elimination of senescent cells can be used to prevent and/or treat autoimmune diseases. The accumulation or removal of senescent cells would modify the microenvironment and therefore the immune reaction. Many other problems caused by immunosenescence can be also partially explained by our hypothesis. Basically, the accumulation of senescent cells is a finely regulated process. Every imbalance in the accumulation of senescent cells between the immune system and the potential target organs can initiate a chronic inflammation or autoimmunity."

Link: http://www.ncbi.nlm.nih.gov/pubmed/19501986