Regular Article LYMPHOID NEOPLASIA

immature KIR2 NK cells exert antileukemic activity toward pediatric BCP-ALL in vivo. • In vivo treatment with low-dose 5-aza-cytidine enhances immature and mature NK-cell counts and promotes antitumor response. Therapeutic natural killer (NK)-cell–mediated alloreactivity toward acute myeloid leukemia has largely been attributed to mismatches between killer immunoglobulin-like receptors (KIRs)onNKcells and their ligands,HLAclass Imolecules,on targetcells.Whileadult acute B-cell precursor leukemia (BCP-ALL) appears to be resistant to NK-cell–mediated lysis, recentdata indicate thatpediatricBCP-ALLmightyetbea targetofNKcells. In thisstudy,we demonstrate in a donor-patient–specific NOD.Cg-Prkdcscid IL2rgtmWjl/Sz (NSG) xenotrans-plantation model that NK cells mediate considerable alloreactivity toward pediatric BCP