A growing body of evidence supports the clinical utility of KIR haplotype analysis, particularly in donor selection strategies aimed at optimizing survival, reducing relapse, and minimizing GVHD. A previous study by Ruggeri et al. provided compelling clinical evidence for the beneficial role of donor NK cell alloreactivity in HLA-mismatched HSCT [38]. The gene discussed is KIR3DL1; the disease is graft versus host disease.