Effects of brazilin on induction of immunological tolerance by sheep red blood cells in C57BL/6 female mice

Brazilin was examined for its effects on the induction of immunological tol erance. Brazilin was administered to C57BL/6 female mice for 2 consecutive days before the immunization with high dose SRBC (10(9) cells) which can pr oduce immunological tolerance. Delayed type hypersensitivity, IgM plaque fo rming cells, ConA induced IL-2 production and mitogen- or antigen-induced p roliferation of lymphocytes were measured as evaluation parameters. Adminis tration of brazilin prior to immunization could keep the DTH and IL-2 produ ction almost optimaly immunized levels. Brazilin also inhibited the elevati on of non-specific suppressor cell activity. ConA induced proliferation of splenocytes in high dose SRBC immunized mice was significantly decreased by pretreatment of brazilin. And this might be one of the reason for augmenta tion of DTH by brazilin. However, IgM plaque forming cells were not affecte d by the treatment of brazilin. These results indicate that brazilin preven ts the induction of immunological tolerance caused by high dose SRBC by sup pressing the elevation of suppressor cell activity and by inhibiting the de crease in IL-2 production in C57BL/6 female mice.