Natural killing can be independent of interferon generated in vitro

PBL produce interferon in response to culture with the tumor cell line K562, but this production of interferon does not correlate with natural cytotoxicity. A basal level of natural killing is independent of interferon generated in vitro. We base this conclusion on the following findings: (i) natural killing and interferon level are not temporally correlated; (ii) preincubation of lymphocytes at 37 °C greatly reduces their ability to produce interferon but does not affect their lytic capacity against K562; and, (iii) addition of an anti-interferon antibody has no effect on NK. We conclude that NK against K562 is not dependent upon or correlated with the level of interferon generated during in vitro assay.