Non-canonical functions of adaptive natural killer cells

Abstract

Abstract Natural killer (NK) cells are critical for the control of cytomegalovirus (CMV) infections in both mice and humans. Subsets of phenotypically and functionally distinct adaptive NK cells accumulate after CMV infection and potentially represent desirable new targets for a preventive CMV vaccine owing to their putatively greater antiviral functionality. However, our lab and others have described a series of non-canonical functions of NK cells that prevent harmful disease outcomes by modulating the responses of other leukocytes. In fact, we now demonstrate that bulk human blood NK cells can suppress CMV-specific T cell responses during in vitro culture. We reason that amplification of these non-canonical functions within an expanded subset of virus-induced adaptive NK cells would be beneficial to health in the context of virus persistence. In order to compare the canonical antiviral and non-canonical immunoregulatory functions of conventional and adaptive NK cells, we first sought to determine if it was possible to expand these subsets using K562 feeder cells with membrane bound IL-21. Similar to our recent longitudinal clinical profiling of adaptive NK cells (Gyurova et al. 2019), we observed variable increase or decrease in the baseline frequencies of adaptive (i.e. FcRγneg) NK cells following ex vivo expansion of cells from disparate healthy donors. Ex vivo expanded NK subsets demonstrated a reduced capacity to kill K562 cells. These results establish a method for obtaining sufficient quantities of adaptive and conventional NK cells for functional evaluation of antiviral and regulatory activity.