KLRK1 and cancer: Using a 10 color flow cytometry panel, we assessed the surface expression of six NK cell receptors, which are known to activate (NKG2D and DNAM-1) or inhibit (NKG2A, PD-1, TIGIT, and TIM-3) NK cell effector functions in a cohort of 16 healthy donors and 20 cancer patients (Table 2).