Impact of Activating Killer Immunoglobulin-Receptor Genotype of the Donor on Outcome of Unrelated Donor - Hematopoietic Stem Cell Transplantation.

Function of NK cells is regulated by a balance between inhibitory and activating signals transmitted through killer immunoglobulin-like receptors (KIR). The goal of the present analysis was to evaluate the impact of donor activating KIR genotype (KIR2DS1 and KIR2DS2 loci) on outcome of unrelated donor-hematopoietic stem cell transplantation (URD-HSCT). Fourty-two URD-HSCT recipients with haematological malignancies, aged 28 (14–48) years (male/female - 26/16) were included in the analysis. The conditioning regimen was myeloablative and based on chemotherapy alone (n=33) or total body irradiation (n=9). Graft-vs-host disease (GVHD) prophylaxis consisted of cyclosporin, methotrexate, and pre-transplant anti-thymocyte globulin. Patients were grouped according to their donors’ activating KIR genotype including two loci: KIR2DS1 and KIR2DS2.

The overall survival at 2.5 years with respect of the donors’ activating KIR genotype was as follows: KIR2DS1(−)DS2(−) (n=15) − 82% (+/−12%), KIR2DS1(+)DS2(−) (n=9) − 78% (+/−14%), KIR2DS1(−)DS2(+)− (n=7) 86% (+/−13%), KIR2DS1(+)DS2(+) (n=11) − 0%. The OS rate differed significantly between KIR2DS1(+)DS2(+) group and the remaining patients: 0% vs. 82% (+/−7%), p=0.03. The difference resulted mainly from higher cumulative incidence of non-relapse mortality in the KIR2DS1(+)DS2(+) group: 100% vs. 18% (+/−8%), p=0.098. The reasons of death in patients with KIR2DS1(+)DS2(+) donors were chronic GVHD (n=4) and acute GVHD (n=1). We conclude that the concomitance of both KIR2DS1 and KIR2DS2 in the donor is associated with high risk of mortality following URD-HSCT, resulting mainly from the incidence of severe GVHD. Whether this effect is associated with the activity of NK cells or KIR-bearing T lymphocytes requires further investigation.