A modification of the natural killer cell assay by substitution of 111indium for 51Chromium

Natural killer (NK) cells are a heterogenous subgroup of lymphocytes possessing the ability to lyse spontaneously various normal, virally infected and transformed cell lines without prior sensitization. Although their lytic activity can be augmented by interferon and interleukin-2, and their function can be inhibited by prostaglandins and corticosteroids, their precise physiological or immunological role has not yet been determined. Roles in anti-tumour surveillance, resistance to viral infection and haemopoietic regulation have been suggested. NK activity has been shown to be defective in a number of diverse conditions such as the Chediak-Higashi syndrome, systemic lupus erythematosus, sarcoidosis and pregnancy. Most current estimations of NK activity rely on a modification of Brunner's cell mediated cytotoxicity assay in which cells bearing NK activity are co-cultured with chromium-labelled K562, a cell line derived from a myeloid leukaemia. However, the work of this and other groups have demonstrated the advantages of indium in isotope-release assays. Hence the experiments described in this report were undertaken to evaluate the use of indium in the NK/K562 assay.

Cell line K562 was maintained in permanent cell culture at 37°C in a humidified atmosphere of 5% CO2, 95% air in RPMI 1640 cell-culture medium supplemented with 10% foetal calf serum (FCS), 100 IU ml^-1 of penicillin, 100 μg ml^-1 of streptomycin and 2 mM of L-glutamine. All cell culture plastics and medium were obtained from Flow or Gibco.