Decrease in Natural Killer (NK) cell populations in peripheral blood of patients with CML who relapsed after treatment interruption. Analysis by flow cytometry of the expression of total CD56+ cells (A), NK cells with profile CD3-CD56 + CD16+ (B) and NKT cells with profile CD3 + CD56 + CD16+ (C) in peripheral blood from the different groups of patients and healthy donors (Healthy donors (●), new CML diagnosis (△), patients On TKI (■), patients Off TKI who did not relapse (▲), patients Off TKI who relapsed (▼)). Each dot corresponds to one sample and lines represent mean ± standard error of the mean (SEM). Statistical significance was calculated using one-way ANOVA and Tukey’s multiple comparisons test. * p < 0.05; *** p < 0.001; **** p < 0.0001.