Immune surveillance and immune evasion of senescent cells.

Senescence, which is defined as a state of stable cell cycle arrest, can occur in all tissues of the body. The surveillance and clearance of senescent cells by the immune system is necessary for tissue homeostasis; when this immune surveillance does not occur efficiently, for example, during tumorigenesis and ageing, it has pathological consequences. For example, if the immune clearance of senescent cells is evaded, such as through recruitment of immunosuppressive cells, expression of immune checkpoint molecules by senescent cells or suppression of antigen presentation, senescent cells accumulate and lead to tissue dysfunction. Therefore, therapeutic modulation of the immune surveillance of senescent cells could be effective for the prevention and treatment of age-associated diseases including cancer. In this Review, we discuss our current understanding of the tissue-specific and context-specific processes that influence immune surveillance of senescent cells. We highlight the need for further research examining senescence across additional settings as well as the role of unexplored immune cell populations.