Homeostatic proliferation of NK cells: friend or foe in cellular immunotherapy?

Evaluation of: Sun JC, Beilke JN, Bezman NA, Lanier LL: Homeostatic proliferation generates long-lived natural killer cells that respond against viral infection. J. Exp. Med. 208(2), 357-368 (2011). NK cells are an important tool in cellular immunotherapy owing to their role in infections and antitumor immunity. Until recently, these cells have been thought to be short-lived cytotoxic effectors that are cleared from the body soon after resolution of an immune response. In the commented study, Sun et al. confirmed that, similar to T cells, NK cells sensed the space in the immune system and underwent homeostatic proliferation in order to provide necessary protection to the body. Moreover, homeostatically driven NK cells persisted in the tissues for a long time without loss of activity. These findings have important consequences for immunotherapy, suggesting that the mechanisms of homeostatic expansion can be deployed in order to expand NK cells for therapeutic purposes in vivo. As homeostatically driven NK cells are long-lived effectors, such therapies can exert prolonged effects for the immunity of the patients.