INVIVO EFFECT OF ASCORBIC-ACID ON ENHANCEMENT OF HUMAN NATURAL-KILLER-CELL ACTIVITY

The in vivo effect of ascorbic acid on human natural killer (NK) cell activity was determined. Twenty control healthy subjects were given as corbic acid at a concentration of 60 mg/kg, and blood was drawn at 0,1 ,2,4,8, 24 and 48 hours after treatment with ascorbic acid. Peripheral Blood Lymphocyte-NK activity was measured by a 4-hr. -Cr-51-release a ssay using K562 tumor cells as targets. Treatment with ascorbic acid w as shown to have a biphasic effect on NK activity: a transient slight suppression between 1 to 2 hrs. (20% of control) was followed by a sig nificant enhancement (an over-shoot) at 8 hrs. that was further increa sed at 24 hrs., then the activity returned to the normal level by 48 h rs. Changes in the activity of ascorbate treated NK cells were inverse ly related to the E:T ratio; namely 231%, 189%, 141% and 127% at 6:1, 12:1, 25:1 and 50:1 E:T ratio respectively. Flow cytometry analysis in dicated no quantitative changes in the NK cell sub-populations post tr eatment with ascorbic acid in the experimental subjects as compared wi th control untreated subjects. Simultaneous to measurement of NK count and activity, ascorbic acid and its uptake by PBL was measured in the plasma. The uptake of the vitamin was maximized at 2-4 hours and main tained at a high level up to 24 hours. We conclude that ascorbic acid is a potent immunomodulator and its effect in enhancement of NK cytoto xicity may explain one mechanism by which ascorbic acid exerts its pro bable anti cancer activity.