Target cell specificity of human natural killer (NK) cells. I. Development of an NK-resistant subline of K562.

By depletion of effector-target conjugates and cloning, a variant of the human leukemic line K562 that is partially resistant to lysis by natural killer (NK) cells when tested under conditions of culture and assay identical to that of the parent has been derived. Its karyotype shows markers similar to the original K562. The resistant phenotype remains stable after over 1 year of continuous passage and persists in multiple replicate subclones. However, it can be killed to a degree equal to the parent by antibody-activated complement, antibody-dependent cellular mechanisms, and by effector cells activated by staphylococcal protein A. These observations and experiments on cold target competition suggest that on its surface there is a significantly decreased, absent, or blocked effective target structure for a major population of unstimulated peripheral blood NK cells.