Fig. 2

General view of NK cell-based immunotherapies. (1) A number of NK cell sources were explored for infusion in adoptive NK cell therapy, including autologous NK cell from patients themselves, peripheral blood or umbilical cord blood and placenta-derived NK cell from healthy donors, and clonal NK cell lines such as NK-92, NK-YS, KHYG-1. (2) Strategies targeting to enhance anti-tumor activity of NK cell including employing CAR structures, using immune checkpoint blockades to block inhibitory receptors on NK cell surfaces, augmenting NK cells by cytokines, applying BiKEs and TriKEs, and inducing memory-like NK cells. (3) Biologically active agents or the “activated” NK cells were then infused to patients, causing lysis of tumor cells and further improving the clinical outcome. Ag, antigen; BiKE, bispecific killer cell engager; CAR, chimeric antigen receptor; CD, cluster of differentiation; IL, interleukin; ICB, immune checkpoint blockade; ML-NKs, memory-like natural killer cells; NKs, natural killer cells; PB, peripheral blood; TriKE, trispecific killer cell engager; UCB, umbilical cord blood