Effect of Missing Killer-immunoglobulin-like Receptor Ligand in Recipients Undergoing HLA Full Matched, Non-T-depleted Sibling Donor Transplantation: a Single Institution Experience of 151 Asian Patients

This retrospective analysis studied the impact of natural killer (NK) alloreactivity based on the missing ligand model, for a cohort of recipients undergoing haemopoietic stem cell transplant without T-cell depletion from HLA full-matched sibling donors. All patients received a uniform myeloablative conditioning regimen and prophylaxis for GVHD. A total of 151 patients were studied, including 62 patients with AML or myelodysplastic syndrome, 42 patients with ALL and 47 patients with CML. We found that 81% of patients had at least one missing KIR-ligand (KIR-L), and HLA-C1 allogroup homozygosity is present in 70% of patients. From multivariate analysis, we observed that the only consistently significant factor that was associated with superior survival was disease stage. Missing KIR-L, whether considering HLA-Bw and HLA-C alleles, without or with HLA-A ligands or narrowing to only HLA-C alleles alone to classify the number of missing KIR-L, did not have any impact on OS or relapse-free survival. This negative finding implies that as the KIR-L composition of recipient is not important in this matched non-T-depleted setting, further immunotherapeutic measures involving adoptive NK cell infusions have to be explored to exploit the benefit of NK alloreactivity for such transplants.