Pre-Transplant Natural Killer Cell Activity Predicts Survival and Tumor Recurrence After Living Donor Liver Transplantation

<b>Background/Objectives</b>: Natural killer (NK) cells are essential mediators of innate immune defense and play a key role in tumor surveillance following liver transplantation (LT). Despite this, the prognostic relevance of pre-transplant NK cell activity in living donor LT (LDLT) has not been fully established. <b>Methods</b>: This retrospective analysis included 134 adult patients who underwent LDLT. NK cell activity was evaluated prior to transplantation using interferon-γ release assays and classified as low (<10 pg/mL) or high (≥10 pg/mL). Overall survival (OS) was assessed for all participants, whereas recurrence-free survival (RFS) was analyzed patients with HCC. <b>Results</b>: Patients classified as having high NK activity (≥10 pg/mL) experienced significantly better overall survival compared to those with low activity (log-rank <i>p</i> = 0.032). In the multivariate analysis, high NK activity showed a strong trend toward improved overall survival (HR, 0.52; 95% CI, 0.26-1.04; <i>p</i> = 0.063). Among recipients with HCC, high NK activity was associated with a markedly improved recurrence-free survival (log-rank <i>p</i> = 0.004). Multivariate Cox regression further established NK activity as an independent factor for tumor recurrence (HR, 0.27; 95% CI, 0.08-0.87; <i>p</i> = 0.028). <b>Conclusions</b>: Pre-transplant NK cell activity independently predicts both survival and recurrence following LDLT.