We compared NK cell responses and muscle strength. Mature CD56dim NK cell responses to K562 leukemia cells showed inverse correlations with muscle strength, as measured by knee extensor peak torque (Figure 6; Table S2 in Supplementary Material), isometric peak torque, and average power (data not shown). Both CD56dim NK cell responses to K562 target cells were significant or trended against strength after factoring in age and sex (Table S2 in Supplementary Material). As expected, skeletal muscle mass correlated with strength in this elderly cohort D (data not shown). Notably, both CD56dim NK cell degranulation (as measured by CD107a) and MIP-1β responses to K562 cells robustly inversely associated with strength after factoring in either thigh muscle mass or leanness (Table S2 in Supplementary Material and data not shown). This indicates that muscle quality substantially and inversely associated with NK cell response to leukemia cells. As with other associations, CMV status did not weaken this inverse correlation (Table S2 in Supplementary Material).