Comparison between natural reactivity (NR) against Candida albicans and natural killer (NK) activity against YAC-1 tumour cells.

Cytotoxic activity against Candida albicans was measured in vitro in a 4-h 51Cr-release assay. The levels of reactivity correlated well with the number of polymorphonuclear cells in the effector population, being augmented by the enrichment of polymorphonuclear granulocytes. To exclude the possible role of contaminating natural killer cells, natural killer activity against tumour cells was compared with natural reactivity against Candida albicans in vitro. The findings indicate that there are many differences between these reactivities including organ and strain distribution, age dependency, adherence to nylon, and susceptibility to modulation by immuno-adjuvants and to treatment with anti-Thy 1.2 antiserum plus complement. These data further define in vitro polymorphonucleate-mediated cytotoxicity against Candida albicans on the basis of the above-mentioned criteria and clearly demonstrate that this in vitro reactivity could not be due to the presence of contaminating natural killer cells in the effector cell population.