Effects of vitamin C on intracytoplasmic cytokine production in human whole blood monocytes and lymphocytes.

Background: Vitamin C (ascorbic acid) is an essential water-soluble nutrient which primarily exerts its effect on immune homeostasis as physiological antioxidant. However, conflicting data exist regarding the effect of vitamin C on the expression of pro-inflammatory cytokines.
Methods: It was the aim of this study to investigate the impact of vitamin C on intracytoplasmic production of pro-inflammatory cytokines in monocytes and lymphocytes by flow cytometry after human whole blood assay.
Results: Vitamin C dose dependently inhibited the LPS-induced number of monocytes producing IL-6 (e.g., 41.0% reduction, p < 0.001, 20 mM vitamin C) and TNF-alpha (e.g., 26.0% reduction, p < 0.005, 20 mM vitamin C). Simultaneously, the number of lymphocytes producing IL-2 after PMA/ionomycin stimulation was dose dependently reduced (e.g., 24.2% inhibition, p < 0.005, 20 mM vitamin C). Notably, the number of IL-1 and IL-8 producing monocytes as well as TNF-alpha and IFN-gamma producing lymphocytes were not significantly affected by 20 mM vitamin C.
Conclusions: These data suggest that vitamin C selectively influences intracytoplasmic cytokine production and therefore, further studies are needed to elucidate the underlying mechanisms of immunomodulation, i.e. regulation of NF kappa B activation which is mandatory for the induction of pro-inflammatory cytokines.