Variance in resistance to natural and antibody‐dependent cellular cytotoxicity and to complement‐mediated lysis among K562 lines

Isolation of sub‐populations of the NK‐sensitive ery‐thro‐leukaemic cell line K562 by limiting dilution techniques has revealed‐marked clonal variation in susceptibility to natural cytotoxicity. Detailed examination of two such lines (E10/P2 and F9/P2) which differed significantly in their susceptibility to both native and activated NK‐cell‐mediated lysis revealed that their differences were stable and independent of culture conditions. The resistant (F9/P2) and sensitive (E10/P2) lines had comparable cold‐inhibitory and effector‐cell adsorption capacities, indicating that differential susceptibility was not attributable to variable expression of NK target structures. F9/P2 was also less susceptible to antibody‐dependent cellular cytotoxicity (ADCC) and complement‐mediated lysis, indicating the existence of variants with a generalized capacity to resist several immunolytic processes.