Phenotypical and functional analyses of natural killer cells from low NK activity individuals among healthy and patient populations.

We investigated the deficiency of natural killer (NK) activity by contrasting healthy individuals with patients. Human NK activities of 125 individuals consisting of 68 healthy donors and 57 patients (36 autoimmune disease and 21 cancer patients) were measured by Eu-DTPA release assay in which the target cells were labeled by nonradioactive materials-Eu-DTPA, and they were phenotypically analyzed with three-color flow cytometry. Furthermore, a part of these donors was functionally studied on NK cells sorted out from PBL. 23.3% of healthy donors and approximately 70% of patients had low NK activity (LNK). In these healthy LNK and patient LNK, the population of CD3-CD16+CD56+ subset in PBL was significantly lower than that of the same subset in healthy individuals with high and medium NK activity (HMNK). The cytotoxicity of CD3-CD16+CD56+ cells sorted out from PBL in healthy LNK and patient LNK were approximately the same with or higher than that in healthy HMNK. No differences were found either in the expression of CD2 and LFA-1 antigens on the CD3-CD56+ NK cells or in the amount of granulous proteins such as perforin and granzyme A in these cells among healthy HMNK, healthy LNK and patient LNK. These results suggested that low NK activity of healthy LNK and patient LNK was more reflected by the diminution of the population of CD3-CD16+CD56+ subset in PBL rather than the functional defects of NK cells. A phenotypical and functional study on healthy LNK has not been reported extensively, and we found several differences between healthy LNK and patient LNK in this study. By stimulation with IL-2, the cytotoxicity of healthy LNK increased more rapidly than that of patient LNK, and at high effector:target cell ratio (> or = 40) it was significantly higher than that of patient LNK. The population of CD3+CD16+/CD56+ subset in PBL of healthy LNK was higher than that of patient LNK, but on the other hand it was about the same as that of healthy HMNK.