Immunologic and anti-immunosuppressive effects of vitamin A

The effects of vitamin A alcohol on cell-mediated immunity in vitro and its ability to prevent the immunosuppressive effects of prednisolone and cyclophosphamide in vivo were studied in mice. Lymphocytes from Calmette-Guérin bacillus (BCG) sensitized mice were stimulated specifically with purified protein derivative (PPD) and nonspecifically with phytohemagglutinin (PHA). In the vitamin A injected animals there was significant enhancement of the spleen lymphocyte transformation not only in the PPD-sensitive cells but also in the T cells at large. In addition, vitamin A was able to restore to normal the cellular and humoral forms of immunity in prednisolone and cyclophosphamide-treated animals. It is suggested that vitamin A in nontoxic doses may have a role in enhancing the responses to weak immunogens and in reversing immunosuppression.