Effects on Lymphocyte-Mediated Immune Responses

Lymphocyte performance is known to be affected by ascorbate concentration. For instance, Cameron et aL (1979) reported an enhancement in immunocompe-tence upon saturation of lymphocytes with ascorbate. Both in vitro and in vivo studies have indicated an immunostimulatory effect of ascorbate on lymphocytic cells (references cited in Jariwalla and Harakeh, 1994). 

The role of vitamin C during immunization was also studied. It was shown that guinea pigs placed on a scorbutic diet after immunization with attenuated Mycobacterium butryicum responded to intradermal injection of tubercular protein. On the other hand, animals made scorbutic prior to the tuberculin inoculation did not respond positively to the tuberculin (Mueller and Kies, 1962 Zweiman et aL, 

The relationship of the above observations in ascorbate-deprived guinea pigs to lymphocyte dysfunction is not clear-cut. Observations by Fraser et al. (1978) on lymphocytes from scorbutic animals suggested a decrease in T lymphocyte count and an increase in B lymphocytes. This phenomenon was reversed when animals were supplemented with a high dose (250 mg/day) of ascorbate. The scorbutic animals had a lower T cell response to concanavalin A (Con A) and an increased B cell response to lipopolysaccharide, compared to animals on diets replenished with ascorbic acid. However, Anthony et al. (1979) did not observe a reduction in T cells in the spleen of scorbutic animals. Because vitamin C-deficient diets can lead to inanition and scorbutic animals are more susceptible to infections, better models are needed to address the relationship between direct effects of vitamin C level and lymphocytic function (Cunningham-Rundles et al., 1993). 

In contrast to the above studies, no increase in proliferation response to mitogen was seen in peripheral blood lymphocytes isolated from healthy elderly persons taking large doses of vitamin C along with other vitamins (Goodwin and Garry, 1983). The same persons, however, did show improved reactivity in a skin test. 

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