Optimized flow cytometry panel for the detection and analysis of human tumor-induced memory-like NK cells

Recent studies indicate that under certain conditions such as viral infection or exposure to pro-inflammatory cytokines, NK cells may acquire features of adaptive immune cells. In this context, various forms of adaptive NK cells have been described, i.e. "liver-resident" memory-like NK cells, cytomegalovirus (CMV)-induced memory NK cells and interleukin (IL)12/15/18 cytokine-induced memory-like (CIML)-NK cells. We recently provided evidence that upon a 7-day co-culture with irradiated leukemia specimens NK cells can exhibit a memory-like phenotype with substantial anti-leukemic functionality. Here, we propose an antibody panel that allows the identification of subtle changes in the activation status and maturation during memory cell conversion of these so-called tumor-induced memory-like (TIML)-NK cells but also the comparison of those with other forms of memory NK cells. As tremendous efforts are currently undertaken to evaluate the clinical benefit of adoptive cell transfer of various forms of NK cells, we here delineate the process of our panel design in detail to provide future researchers with the means to optimize the flow cytometric analysis of various forms of memory NK cells within their clinical trial protocols.