We analyzed the influence of donor killer-cell immunoglobulin-like receptor (KIR) gene haplotypes on the risk of relapse and probability of event-free survival (EFS) in children with acute lymphoblastic leukemia (ALL) who received HLA-haploidentical transplantation of ex vivo T-cell depleted peripheral blood stem cells. The KIR gene haplotype was evaluated in 85 donors and the KIR B-content score was determined in the 63 KIR haplotype-B donors. Patients transplanted from a KIR haplotype-B donor had a significantly better EFS than those transplanted from a KIR A-donor (50.6% versus 29.5%, respectively, p=0.033). Moreover, a high donor KIR B-content score was associated with a significantly reduced risk of relapse (Log-rank test for trend p=0.026). These data indicate that KIR genotyping should be included in the donor selection algorithm for haploidentical transplantation in children with ALL with the aim of choosing, whenever possible, a KIR haplotype-B donor with a high KIR B-content score.
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