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.