Specific combinations of donor and recipient KIR-HLA genotypes predict for large differences in outcome after cord blood transplantation

The ability of cord blood transplantation (CBT) to prevent relapse depends partly on donor natural killer (NK) cell alloreactivity. NK effector function depends on specific killer-cell immunoglobulin-like receptors (KIR) and HLA interactions. Thus, it is important to identify optimal combinations of KIR-HLA genotypes in donors and recipients that could improve CBT outcome. We studied clinical data, KIR and HLA genotypes and NK-cell reconstitution in CBT patients (n=110). Results were validated in an independent cohort (n=94). HLA-KIR genotyping of recipient germline and transplanted CB grafts predicted for large differences in outcome. Patients homozygous for HLA-C2 group alleles had higher 1-year relapse rate and worse survival after CBT than did HLA-C1/C1 or HLA-C1/C2 ( HLA-C1/x ) patients: 67.8% vs. 26.0% (p HLA-C1/x patients receiving a CB graft with the combined HLA-C1-KIR2DL2/L3/S2 genotype had lower 1-year relapse rate (6.7% vs. 40.1%, p=0.002) and superior survival (74.2% vs. 41.3%, p=0.003) compared to recipients of grafts lacking KIR2DS2 or HLA-C1 . HLA-C2/C2 patients had lower relapse rate (44.7% vs. 93.4%, p=0.001) and better survival (30.1% vs 0%, p=0.01) if they received a graft with the combined HLA-C2-KIR2DL1/S1 genotype. Relapsed/refractory disease at CBT, recipient HLA-C2/C2 genotype and donor HLA-KIR genotype were independent predictors of outcome. Thus, we propose the inclusion of KIR genotyping in graft selection criteria for CBT. HLA-C1/x patients should receive a HLA-C1-KIR2DL2/L3/S2 CB graft, while HLA-C2/C2 patients may benefit from an HLA-C2-KIR2DL1/S1 graft.