Survival correlates with increased KIR expression on donor-derived NK cells after transplantation. Kaplan-Meier survival estimates in recipients of UBM or TCD transplants are shown below. The ratios of day +100, donor-derived recipient CD3^-/CD56⁺ NK cells to donor cells expressing KIR were analyzed as described. The results were analyzed with a Cox multivariate proportionate hazards model that included KIR expression, percentage of CD56^+bright cells, IFN-γ production, and survival (n = 72). The recipients were further stratified by KIR expression ratio of equal to or more than 0.6 or less than 0.6, which was the mean R/D ratio of all samples (left panel). Stratification based on graft type (UBM, n = 35; TCD, n = 37) accentuates the correlation of KIR expression with survival but was not an independent predictor (right panel).