HLA-C and acute leukemia: Cox regression multivariate analysis of total acute leukemia patients showed that KIR2DL1/HLA-C*04 interaction was an independent prognostic factor for EFS (HR = 4.795, p = 0.005, Harrell C-statistic = 0.798 ± 0.051) and OS (HR = 6.731, p = 0.005, Harrell C-statistic = 0.837 ± 0.047), as was the risk status at enrollment (HR = 2.209, p = 0.013 for EFS and HR = 2.182, p = 0.033 for OS) when analyzed together with sex, age, the type of leukemia and the low/high expression of ULBP-1 on leukemic blast cells (Figure 6A).