Studies of an immunomodulator, swainsonine. I. Enhancement of immune response by swainsonine in vitro.

Swainsonine isolated from Metarhizium sp., was found to enhance the activities of the mouse immune system in vitro. Concanavalin A stimulated lymphocyte proliferation and proliferative response in mixed lymphocytes culture, which were suppressed by immunosuppressive factor obtained from serum of sarcoma 180 tumor bearing mouse, were restored to normal levels by the addition of swainsonine. Furthermore, the concanavalin A induced incorporation of [3H]thymidine into mouse spleen cells was remarkably increased by treatment with swainsonine over a wide dose range, From studies using fluorescence activated cell sorting, swainsonine was shown to enhance the expression of concanavalin A receptors of spleen cells.