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Blood, 26 March 2009, Vol. 113, No. 13, pp. 3119-3129. Prepublished online as a Blood First Edition Paper on October 22, 2008; DOI 10.1182/blood-2008-06-164103.
TRANSPLANTATION Anti-leukemia activity of alloreactive NK cells in KIR ligand-mismatched haploidentical HSCT for pediatric patients: evaluation of the functional role of activating KIR and redefinition of inhibitory KIR specificity1 Immunologia, Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy; 2 Dipartimento di Medicina Sperimentale, Università di Genova, Genoa, Italy; 3 Immunologia Clinica e Sperimentale, Istituto Giannina Gaslini, Genoa, Italy; 4 Oncoematologia Pediatrica, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Policlinico San Matteo; Dipartimento di Scienze Pediatriche, Università di Pavia, Pavia, Italy; 5 Centre d'Immunologie de Marseille-Luminy, Université de la Méditeranée, Marseille, France; 6 Laboratorio di Tipizzazione Tissutale and 7 Laboratorio di Ricerca Trapianto di Midollo Osseo e Oncoematologia Pediatrica, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy; and 8 Centro di Eccellenza per la Ricerca Biomedica, Università di Genova, Genoa, Italy We analyzed 21 children with leukemia receiving haploidentical hematopoietic stem cell transplantation (haplo-HSCT) from killer immunoglobulin (Ig)–like receptors (KIR) ligand-mismatched donors. We showed that, in most transplantation patients, variable proportions of donor-derived alloreactive natural killer (NK) cells displaying anti-leukemia activity were generated and maintained even late after transplantation. This was assessed through analysis of donor KIR genotype, as well as through phenotypic and functional analyses of NK cells, both at the polyclonal and clonal level. Donor-derived KIR2DL1+ NK cells isolated from the recipient displayed the expected capability of selectively killing C1/C1 target cells, including patient leukemia blasts. Differently, KIR2DL2/3+ NK cells displayed poor alloreactivity against leukemia cells carrying human leukocyte antigen (HLA) alleles belonging to C2 group. Unexpectedly, this was due to recognition of C2 by KIR2DL2/3, as revealed by receptor blocking experiments and by binding assays of soluble KIR to HLA-C transfectants. Remarkably, however, C2/C2 leukemia blasts were killed by KIR2DL2/3+ (or by NKG2A+) NK cells that coexpressed KIR2DS1. This could be explained by the ability of KIR2DS1 to directly recognize C2 on leukemia cells. A role of the KIR2DS2 activating receptor in leukemia cell lysis could not be demonstrated. Altogether, these results may have important clinical implications for the selection of optimal donors for haplo-HSCT.
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