Clinical applications of adoptive natural killer cell immunotherapy for cancer: current status and future prospects.

Natural killer (NK) cells are cytotoxic and cytokine-producing lymphocytes involved in the immune defense against viral infections and tumors. NK cells activated with cytokines, such as interleukin-2, have been used since the 1980s as adoptive immunotherapy against cancer. NK cell alloreactivity has been demonstrated to enhance control of acute myeloid leukemia relapse and greatly reduce the risk of graft-versus-host disease in HLA haplotype-mismatched hematopoietic transplantation, and has been explored as a tool for adoptive immunotherapy for cancer patients. Future manipulation to improve NK cell adoptive immunotherapy by means of increasing target recognition and reducing inhibitory signaling is being explored.