Production and measurement of cytotoxic factor/s produced by lymphocytes in response to an NK-sensitive tumour cell line

Previous work has shown that patients with advanced hepatocellular carcinoma (HCC) have defective natural killer cell mediated cytotoxicity (NK CMC). Recently factors released by natural killer (NK) cells, termed natural killer cytotoxic factors (NKCF), have been described as being the NK-lytic mediators. Since interleukin 1 (IL-1) and NKCF have similar properties and are both released by NK cells upon interaction with an NK-sensitive target cell, a possible link between these two factors was investigated. Using the same procedures for the induction and measurement of NKCF a cytotoxic factor which will be referred to as CF, was identified. During this procedures chromium and tritium were used as radioactive markers and the methods for the measurements are described. Using dicontinuous Percoll gradients, the release of CF activity was found to be highest in cell fractions that had been enriched for large granular lymphocytes (LGL). Although cytotoxic activity of CF could be blocked by anti IL-1 antiserum, the proteins responsible for both IL-1 and CF activities could be separated. These results suggest that although CF and IL-1 are not the same proteins, they are closely related. The NK CMC of peripheral blood mononuclear (PBM) cells from patients with HCC was found to be defective, however, unexpectedly the CF released by the same cells was found to be normal. When PBM cells were treated with monensin, the CF activity released was found to be unimpaired. These results indicate that the release of CF activity does not correlate with NK CMC and suggests that NK cells have more than one function. Thus in HCC patients, whilst the NK CMC function is defective their ability to release CF/NKCF, appears to be unimpaired. CF is unlikely to be a constituent of the cytotoxic granules