In vivo monitoring of natural killer cell trafficking during tumor immunotherapy.

Natural killer (NK) cells are a crucial part of the innate immune system and play critical roles in host anti-viral, anti-microbial, and antitumor responses. The elucidation of NK cell biology and their therapeutic use are actively being pursued with 200 clinical trials currently underway. In this review, we outline the role of NK cells in cancer immunotherapies and summarize current noninvasive imaging technologies used to track NK cells in vivo to investigate mechanisms of action, develop new therapies, and evaluate efficacy of adoptive transfer.