Abstract
The effects of differentiation inducers on the sensitivity of two human myeloid cell lines, K562 and HL-60, to natural killer (NK) cell lysis were examined. K562 cells treated with 12-O-tetradecanoyl phorbol-13-acetate (TPA) and HL-60 cells treated with either TPA or dimethylsulfoxide (DMSO) not only became less sensitive NK targets, but also became less competitive in cold target inhibition experiments. Target binding cell assays revealed that TPA-treated target cells bound fewer NK effector cells than did untreated targets. TPA treatment renders K562 and HL-60 target cells more susceptible to hypotonic lysis, indicating that the decreased NK sensitivity is not due to altered osmotic fragility. The observed reduction in sensitivity to NK lysis was not apparently mediated by interferon (IFN) released by the target cells, as neither alpha nor gamma IFN were detected in culture supernatants. Furthermore, the effects of TPA were additive to the known protective effect of IFN on NK target cells. In contrast to the parent line, a subclone of HL-60 resistant to chemically induced differentiation did not become a less sensitive target after exposure to TPA. These observations with myeloid and erythroid target cells imply that the reduced killing of the TPA-treated cells was secondary to impaired recognition of the target by the effector, and that the state of cellular differentiation is a major determinant of susceptibility to NK cell-mediated lysis.
Published Version
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