Killer-cell immunoglobulin-like receptor ligand compatibility in the outcome of Finnish unrelated donor hematopoietic stem cell transplantation.

Incompatibility in killer-cell immunoglobulin-like receptor (KIR) ligand between recipient and donor of hematopoietic stem cell transplantation has been reported to lead to natural killer (NK) cell activation. This activation may result in better transplantation outcome through reduced risk of graft-versus-host (GvH) disease, relapse and mortality. In the present study the effect of KIR ligand incompatibility was investigated retrospectively in 186 unrelated stem cell transplantations performed in Finland during years 1993-2004. No clear evidence for a better outcome in cases with KIR ligand incompatibility was obtained. Transplantation-related mortality was 64% in Kaplan-Meier analysis in the GvH direction KIR ligand-mismatched group and 33% in the KIR ligand-matched group. This difference was statistically non-significant. Consequently, no support could be obtained for a beneficial effect of KIR ligand incompatibility in the present set of unrelated donor transplantations.