The determination of natural killer activity of human peripheral blood lymphocytes by measuring the DNA-synthesis of proliferating target cells (K 562 cell line).

Natural killer (NK) activity of human peripheral blood lymphocytes was determined by measuring 3H-thymidine incorporation into proliferating highly NK-sensitive K 562 target cells alone and in the presence of effector cells. Although the absolute figures varied, depending mostly on the strength of DNA-synthesis of the target cells on the day of the assay, the results were highly reproducible and compared well with those of the 51Cr-release assay (CRA). The method was extremely simple and less tedious than CRA. The interpretation of the data was facilitated by including known control cells of low and high NK activity. The cells less sensitive to NK activity did not seem to be suited for this kind of assay.