EFFECTS OF SUBCHRONIC EXPOSURE TO CARAMEL COLOR-III ON THE IMMUNE-SYSTEM IN MICE

Administration of Caramel Colour III is associated with lymphopenia in laboratory animals, especially if the animals are fed a vitamin B-6-d eficient diet. Recently, functional immunological alterations in rats exposed to Caramel Colour III have been reported. The component of Car amel Colour III that is responsible for the immunological effects has been shown to be 2-acetyl-4-tetrahydroxybutyl imidazole (THI). In the present study, female Balb/c mice fed a diet with a relatively high vi tamin B-6 content were exposed to 2 or 10% of a commercial Caramel Col our III preparation with a low THI content (less than 25 ppm) in the d rinking water for 9 wk. Although this treatment did not induce a lymph openia in the exposed mice, flow cytometric analysis of lymphocyte sub populations demonstrated reductions in the CD4(+) and CD8(+) cell popu lations. In addition, the proliferative response of spleen cells to B and T cell mitogens was significantly reduced in the mice exposed to 2 % Caramel Colour III, No changes were observed in natural killer cell activity or in the humoral antibody response to a viral antigen. The r esults indicate that Caramel Colour III that meets the specified limit of less than 25mg THI/kg may, nevertheless, interfere with the lympho id system in mice with an adequate vitamin B-6 status.