Effects of vitamin C on the immune system in the guinea pig

Humans and guinea pigs require vitamin C in the diet. As yet, the exact function of the vitamin in the body and the optimum concentrations remain unknown. The guinea pig serves as a model for nutritional and immunological studies to elucidate the role of the vitamin. In this study, guinea pigs were given supplemental doses of either 500 mg, 250 mg or 0 mg vitamin C per day in their drinking water and the functioning of the immune system was assessed. Serum ascorbate levels were monitored over an eight week period and the animals were inspected for signs of scurvy. The delayed type hypersensitivity reaction to mycobacterial antigens, a T lymphocyte-dependent function, was recorded as the diameter of the induration formed at the injection site. The total number of leukocytes per cu mm of blood was counted and the relative percentage of T cells was determined by the lymphocyte-erythrocyte resetting procedure. Guinea pig serum IgG levels were measured by radial immunodiffusion as antibody production is aided by a subset of T cells. While the animals in the 500 mg supplement group enjoyed a longer lifespan than those in the 250 mg supplement group, the latter displayed slightly higher results in all parameters: their serum ascorbate level continued to rise while the level of the higher dosage group declined; they had greater counts of both total leukocytes and T cells as well as a higher immunoglobulin titer. Values for both supplement groups were higher than for the controls. These results obtained in guinea pigs indicate that vitamin C supplementation augments the level of measurable indicators of the function of the immune system; they further suggest, but do not define, an optimum supplementation level. Additional experiments using more sensitive techniques should be carried out to determine the most beneficial concentration range.