KIR alloreactivity based on the receptor-ligand model is associated with improved clinical outcomes of allogeneic hematopoietic stem cell transplantation: Result of single center prospective study

Receptors on natural killer (NK) cells, named killer immunoglobulin-like receptors (KIRs), recognize HLA class I alleles. Patients (n = 59) who received allogeneic hematopoietic stem cell transplantation (HSCT) from either a related (n = 17) or unrelated donor (n = 42) in Samsung Medical Center (Seoul, South Korea) were included. KIR mismatch was defined as incompatibility between the donor KIR and recipient KIR ligand (receptor-ligand model), and all cases were classified into the two broad haplotypes of KIR A and B. Patients with acute leukemia (n = 51, 86.4%) or myelodysplastic syndrome (n = 8, 13.6%) were included. Peripheral blood was used as the source of stem cells in all patients. Kaplan-Meier survival curves for overall survival (OS), disease-free survival (DFS), and cumulative incidence of relapse (CIR) favored recipients with a KIR-mismatched donor, although the differences were not statistically significant. In multivariate analysis, KIR mismatch was an independent prognostic indicator of a better OS (P = 0.010, HR = 0.148, 95% CI 0.034-0.639), DFS (P = 0.022, HR = 0.237, 95% CI 0.069-0.815), and CIR (P = 0.031, HR = 0.117, 95% CI 0.017-0.823). OS, DFS, and CIR did not differ significantly between the KIR A and B haplotypes.