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, 20mM vitamin C) and TNF-α (e.g., 26.0% reduction, p<0.005, 20mM 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, 20mM vitamin C). Notably, the number of IL-1 and IL-8 producing monocytes as well as TNF-α and IFN-γ producing lymphocytes were not significantly affected by 20mM 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 NFκB activation which is mandatory for the induction of pro-inflammatory cytokines.