concanavalin-a and Ascorbic-Acid-Deficiency

The influence of ascorbic acid (AA) on lymphocyte functions was examined in vitro and ex vivo in peripheral blood mononuclear cells (PBMC) of vitamin C-deficient pigs, which are unable to synthesise ascorbic acid. AA is accumulated to physiological levels in PBMC in vitro. The cell proliferation induced by T lymphocyte mitogens was unaltered at all AA concentrations tested (0-400 micrograms/ml, i.e., 0-2.3 mM). Conversely, the response to pokeweed mitogen (PWM) which activates T and B lymphocytes was significantly reduced with increasing intracellular and extracellular AA concentrations. The response to lipopolysaccharide (LPS) showed a tendency to increase at low (9 microM) and was significantly reduced at high AA concentrations (> 36 microM). The IL2 production induced by PWM (but not by concanavalin A (Con A) or phytohemagglutinin (PHA)) decreased at high AA (> 142 microM). In contrast, IL6 production induced by mitogens was not dependent on AA concentrations. In concordance with these results, AA-depleted PBMC which were obtained from pigs that were fed an AA-free diet, displayed an increasing response to LPS and PWM. Collectively, the data indicate that ascorbic acid selectively influences the proliferation of B lymphocytes and negatively acts on IL2 production by T lymphocytes when a threshold of saturation is exceeded.

Topics: Animals; Ascorbic Acid; Ascorbic Acid Deficiency; B-Lymphocytes; Cells, Cultured; Concanavalin A; Interleukin-2; Interleukin-6; Lipopolysaccharides; Lymphocyte Activation; Lymphocytes; Mitogens; Phytohemagglutinins; Pokeweed Mitogens; Swine; T-Lymphocytes