[Heterogeneity of a KU-2 cell line derived from human renal cell carcinoma--differential susceptibilities of its sublines to NK cell-mediated cytotoxicity].

Natural killer (NK) cell activity against 4 different sublines of a permanent cell line KU-2 derived from human renal cell carcinoma were measured by 51Cr-release assay and single cell binding assay. KU-2 and its sublines exhibited different susceptibilities of interferon (IFN)-augmented NK cell cytotoxicity. Moreover, 2 out of 4 sublines changed in susceptibility to NK cell cytotoxicity in a few months. Along with the direct assay for NK cell activity, frequency and kinetics of NK cell-mediated cytotoxicity against 3 sublines were studied by single cell binding assay where spontaneous killing of target cells was directly visualized by the reading of trypan blue uptake into target cells among effector-target cell conjugates. The frequency of killer cells among conjugates was dependent on the susceptibility of the sublines to the IFN-augmented NK cell cytotoxicity. These results suggested the following: KU-2 cell line was not homogeneous but composed of a heterogeneous population of cells and even in one subline derived from a clone, the cells with different susceptibilities to NK cell-mediated cytotoxicity developed spontaneously in ordinary culture conditions with the passage of a certain period of time.