HLA and KIR genotyping correlates with relapse after T-cell-replete haploidentical transplantation in chronic myeloid leukaemia patients

Background: Conflicting results have been reported regarding the predicative roles of alloreactive natural killer (NK) cells on the outcomes of transplantation in leukaemia patients. Methods: We prospectively analysed the human leukocyte antigen (HLA) typing of donor–recipient pairs and the KIR typing of the donors in 97 CML patients to address the predictive roles of NK cells in relapse undergoing T-cell-replete haploidentical transplantation. Results: Patients with class I ligands for the donor-inhibitory KIR gene exhibited decreased molecular and haematologic relapse rates ( P =0.003 and P =0.015, respectively). There was a significantly reduced risk of molecular and haematologic relapse in patients with HLA-C1C2 or C2C2 who accepted donors with KIR2DS1 or in patients with HLA-Bw4 who accepted donors with KIR3DS1 (‘recipient with relevant KIR ligand for donor-activating KIR’, n =25), compared with the remaining transplants ( n =72, P =0.009 and P =0.009, respectively). In addition, the presence of class I ligand in the recipients of donor-activating KIR contributed to a decreased relapse rate in patients lacking class I ligand in the recipient of donor-inhibitory KIR ( P =0.04 and P =0.03, respectively). Conclusions: This study suggests that the presence of class I ligands for the donor-activating or donor-inhibitory KIR gene in the recipient might confer some protection against leukaemic relapse in T-cell-replete haploidentical transplantation.