An investigation of the immune suppression induced by some saikosaponin derivatives

The relationship between lymphocyte activation by purified plant glycoside and the suppression of antibodies against sheep erythrocytes was investigated by an adoptive cell transfer system. Glycosides are one of the main components of Shôsaikotô--famous hematopoietic remedies of oriental medicine. In earlier reports, BALB/c mice treated with these drugs, suppressed the plaque-forming cell (PFC) response to T-dependent antigens. In contrast, the PFC response was enhanced for T-independent antigens. In this communication, an experiment was designed to determine the nature of the suppressive factor(s) produced in treated mice. Mice were orally or intraperitoneally administered 1 mg/kg of five types of purified SS derivatives every other day on five consecutive occasions. Spleen cells and serum were prepared from SS-treated mice and were then passively transferred to recipient mice. On the spleen cells (and not any of the sera) from drug-treated hosts effectively suppressed the PFC in recipients. The spleen cells of treated mice were further divided into adherent and non-adherent cells; each cell type was transferred into recipient animals. The observed suppressive activity was clearly detected in the non-adherent cell population. A subsequent analysis of the lymphocyte subpopulation revealed that Lyt.1.1 negative and Lyt.2.2 positive cells were responsible for this suppression. It was concluded that some SS derivatives elevate the activities of the major immunocyte population, with suppressor cell activity predominating.