Activating killer immunoglobulin-like receptor incompatibilities enhance graft-versus-host disease and affect survival after allogeneic hematopoietic stem cell transplantation.

Objectives:  Killer immunoglobulin-like receptors (KIRs) regulate function of natural killer (NK) cells and a subset of T cells. In this study, we prospectively evaluated the impact of donor and recipient activating KIR genes on outcome of allogeneic hematopoietic stem cell transplantation (alloHSCT) for patients with hematological malignancies. Methods:  One-hundred consecutive recipients of myeloablative transplantation and their donors were tested for KIR genotype as well as for immune reconstitution, including activating KIR expression on NK cells and T cells. Results:  In a multivariate analysis, mismatches of particular activating KIRs such that the patient was negative and the donor was positive (P−D+) resulted in increased risk of acute (KIR2DS1) and chronic (KIR2DS3) graft-versus-host disease (GVHD) as well as relapse (KIR2DS5). KIR2DS1 incompatibility in the same direction in the presence of HLA-C-group 2 ligand in recipient was associated with reduced overall (risk ratio, RR = 3.01; P = 0.01) and disease-free survival (RR = 2.92, P = 0.03). Activating mismatches in P−D+ direction resulted in decreased CD4+ : CD8+ T-cell ratio up to 1 yr after alloHSCT, as a consequence of decreased CD3+CD4+ number within the first 100 d and increased CD3+CD8+ number in later time-points. Among six evaluated patients, expression of activating KIRs on NK cells and T cells was particularly prominent for those developing intestinal GVHD. Conclusion:  Our findings indicate that the presence of particular activating KIRs in donor with their absence in recipient enhances GVHD, which is not accompanied by graft-versus-leukemia effect. Evaluation of activating KIR genotype may allow optimization of both donor selection and transplantation procedure in order to avoid GVHD.