INFLUENCE OF ASCORBIC-ACID ON THE RESPONSE TO MITOGENS AND INTERLEUKIN PRODUCTION OF PORCINE LYMPHOCYTES

The influence of ascorbic acid (AA) on lymphocyte functions was examin ed in vitro and ex vivo in peripheral blood mononuclear cells (PBMC) o f vitamin C-deficient pigs, which are unable to synthesise ascorbic ac id. AA is accumulated to physiological levels in PBMC in vitro. The ce ll proliferation induced by T lymphocyte mitogens was unaltered at all AA concentrations tested (0-400 mu g/ml, i.e. 0-23 mM). Conversely, t he response to pokeweed mitogen (PWM) which activates T and B lymphocy tes as significantly reduced with increasing intracellular and extrace llular AA concentrations. The response to lipopolysaccharide (LPS) sho wed a tendency to increase at low (9 mu M) and was significantly reduc ed at high AA concentrations (>36 mu M). The IL2 production induced by PWM (but not by concanavalin A (Con A) or phytohemagglutinin (PHA)) d ecreased at high AA (>142 mu M). In contrast, IL6 production induced b y mitogens was not dependent on AA concentrations. In concordance with these results, AA-depleted PBMC which were obtained from pigs that we re fed an AA-free diet, displayed an increasing response to LPS and PW M. Collectively, the data indicate that ascorbic acid selectively infl uences the proliferation of B lymphocytes and negatively acts on IL2 p roduction by T lymphocytes when a threshold of saturation is exceeded.