KIR-HLA receptor-ligand mismatch associated with a graft-versus-tumor effect in haploidentical stem cell transplantation for pediatric metastatic solid tumors

Killer immunoglobulin‐like receptors (KIRs) on natural killer cells (NKs) recognize groups of human leukocyte antigen (HLA) class I alleles. Cells without an inhibitory HLA ligand may trigger NK activation. Reduced risk of relapse has been reported in malignant hematologic diseases after haploidentical transplantation when HLA ligands against the inhibitory KIRs present in the donor were absent in the recipient. We performed haploidentical transplant in three children with refractory solid tumors. Our results showed that beneficial antitumor effects could be observed in the presence of inhibitory KIR–HLA mismatch. These preliminary results suggest a possible association between disease control and NK cell alloreactivity. Pediatr Blood Cancer 2009;53:120–124. © 2009 Wiley‐Liss, Inc.