In vivo augmentation of natural killer cell activity by Candida albicans

We determined in vivo effects of Candida albicans (CA) on murine natural killer (NK) cell activity. C3H mice were treated with heat-killed CA and splenic NK cell activity assayed at 2, 7, 30 and 50 days post treatment. A single injection of CA caused enhancement of splenic NK activity as measured in a 4 h 51Cr-release assay. Peak NK activity was detected at day 7 and persisted for up to 30 days, after which it declined to control values at 50 days. Augmentation of NK activity by CA resulted from enhanced lytic effects of NK cells, which was independent of effector cell binding capacity. Moreover, enhanced NK activity was associated with an increase in the proliferative response to CA antigen and in splenic cellularity when compared to saline injected controls. Thus, CA seems to act as an immunomodulator causing an augmentation of NK cell activity. Since other biological response modifiers (BRMs) do not show the same strength of augmentation, CA could be used as a new BRM having possible anticancer effects.