In vitro immunosuppressive properties of the plant alkaloid tetrandrine.

Tetrandrine is an extract of the creeper Stephania tetrandra used in traditional Chinese medicine for the treatment of rheumatic diseases. It has recently been shown to retard and even reverse the lesions of silicosis in humans and rats. Data presented in this report indicate that tetrandrine has potent immunosuppressive properties. Mitogen-induced lymphoproliferative responses were markedly reduced even when tetrandrine was added after the initiation of cultures. In vitro antibody synthesis by B cells was also suppressed by tetrandrine, as was the natural killer cell-mediated lysis of K562 cells. It does not interfere with receptor-ligand binding, but does affect the inositol triphosphate second messenger system. These effects of tetrandrine were observed at nontoxic concentrations as shown by lymphocyte viability studies. These results indicate that tetrandrine possesses potent immunosuppressive properties, and may warrant further study in animal models of chronic inflammatory conditions, autoimmune diseases and transplant rejection.