The beneficial impact of missing KIR ligands and absence of donor KIR2DS3 gene on outcome following unrelated hematopoietic SCT for myeloid leukemia in the Chinese population

The effect of natural killer (NK) cell alloreactivity on the outcome of unrelated hematopoietic SCT (HSCT) remains a topic of debate. NK cell alloreactivity after allogeneic HSCT is regulated by killer-cell Ig-like receptors (KIRs). To investigate the influence of KIRs on outcome after unrelated HSCT, we retrospectively analyzed the HLA and KIR genotypes of 116 donor–recipient pairs. We found that missing KIR ligands in recipients were significantly associated with a decreased leukemic relapse risk ( P =0.019, HR=0.329), mainly in myeloid disease ( P =0.003, HR=0.193). This beneficial effect was seen in AML/myelodysplastic syndrome and also in chronic myeloid leukemia. In myeloid disease, missing KIR ligands also improved 5-year OS ( P =0.034, HR=0.430) and disease-free survival (DFS) ( P =0.024, HR=0.445). Meanwhile, the presence of donor-activating KIR2DS3 gene was associated with increased relapse risk ( P =0.003, HR=5.046), decreased OS ( P =0.004, HR=3.181) and DFS ( P =0.003, HR=2.919) in myeloid disease. No effect was seen in patients with lymphoid disease. Our study indicated that, in unrelated HSCT for myeloid leukemia, missing KIR ligands in recipients offered a lower relapse risk and a long-term survival advantage. The presence of KIR2DS3 in the donor was an important risk factor for myeloid leukemia.