CD56^+Bright and CD56^+DIM natural killer cells in patients with chronic myelogenous leukemia (CML) demonstrate progressive decreases in number. cytotoxicity, clonogenic frequency. and proliferation on a per cell basis

Human natural killer cells (NK) require accessory cell-derived contact and soluble factors for maximal expansion. We demonstrate that M2-10B4 accessory cell soluble factors increase expansion of both CD56^+dim and CD56^+brigt normal NK while addition of M2-10B4 stromal ligands further augments only expansion of normal CD56^+bright NK. Utilizing single cell sorting of CDSe^+bright NK, M2-10B4 soluble and contact factors independently increase both recruitment of clonogenic NK and proliferation on a per cell basis, This well-defined M2-10B4 accessory cell system was used to investigate potential NK defects in 22 CML patients. Absolute circulating NK/cc progressively decreased from 63,700±6400 in normal donors (n=15), to 40,700±6700 in early chronic phase (ECP, n=7), to 3I,000±5100 in late chronic phase/advanced phase (LCP/AP, nail), and to 10,70015200 in blast crisis (BC, n=4) CML. Even after NK purification to correct for differences in NK number, resting NK cytotoxicity against K562 tumor targets is significantly reduced in CML patients compared to normal controls. However, this reduced cytotoxicity can be corrected by 18 hour incnhaltnn with 1000 T I/ml rf!.-2 Whn nlatftd in limitino Hiliitinn nn viahl M2-IOB4. we show that both NK clonogenic frequency and proliferative capacity are significantly reduced as CML progresses demonstrating an inherent defect in their ability to respond to normal NK stimuli. Although NK cloning efficiency between normal donors and ECP CML uatients was the same, significant differences were observed in (1) absolute number of circulating CD56⁺/CD3- NK, (2) resting cytotoxic function and (3) proliferation on a per cell basis. Therefore, even ECP CML NK exhibit characteristic abnormalities suggesting early and progressive influences of CML on the immune system.