Vitamin C and immunity: natural killer (NK) cell factor.

The influence of a vitamin C regimen, 250 mg% in the drinking water, on natural killer (NK) cell activity was investigated in three highly inbred strains of mice. Spleen effector cells from these donors, both tap water control and experimental after 4-5 weeks, were tested against YAC-1 murine lymphoma target cells in a 4-hour 51Cr release assay. Ascorbate treatment was observed to be without effect on NK activity in the autoimmune- and lymphoma-prone NZB strain as well as in the normal and low cancer-incidence BALB/c and DBA/2. The relative levels of hemopoietic stem cells, purported to be decisive in determining NK levels, were of a similar order in these three strains as their relative NK activities. It appears that the established association of vitamin C with modulation of the immune response, as observed in activation of T cell-mediated immunity and the enhancement of interferon production, would not include alterations in natural cytotoxic reactivity.