Leukemia cells induce in vitro down-regulation of NCRs. Effect of leukemia-cell coculture with differentiating healthy donor NK cells (A) and resting healthy donor NCR^bright NK cells (B). (A) MFI of surface staining with anti-NKp30 and anti-NKp46 PE-conjugated mAbs on CD45^high CD3⁻CD56⁺ NK cells are represented. ▪ represent NK cells differentiated from CD34⁺ progenitors in the presence of irradiated allogeneic PBMCs. □ represent NK cells differentiated in the presence of irradiated blasts from patients with NCR^dull AML. ▨ represent NK cells differentiated in the presence of irradiated blasts from patients with NCR^bright AML. NK cells were analyzed 15 days after the starting culture of CD34⁺ cells. Data represent the mean ± SD of 6 independent experiments. *P = .05 (NS). (B) MFI of surface staining of anti-NKp30 PE-conjugated mAb on resting NCR^bright NK cells from healthy donors. Expression of NKp30 was explored on NK cells cultured for 1 to 5 days in the presence of nonirradiated blasts from patients with NCR^dull AML (□) or nonirradiated healthy donor PBMCs (▪). Data present mean MFI ± SD of at least 3 independent experiments.