Effect of saikosaponin derivatives upon the immune response against T-dependent and T-independent antigens in mice.

Effect of water soluble extracts and purified derivatives from the root of the plant Bupletum falcatum L. upon the immune response of BALB/c mice was investigated using heterologous erythrocytes and bacterial lipopolysaccharide. This Chinese Medicine is famous for its reputed anti-inflammatory, anti-tumor and other biological activities, and has been widely used alone or in a complexed form since ancient times in Oriental Countries. The effect on immune responsiveness of this drug was judged by the measurement of antibody secreting cells causing localized hemolysis in agar gel. The purified derivatives, Saikosaponin (SS) a and d, suppressed anti-SRBC plaque-forming cells (PFC), but the other derivatives, b1 and b2 and c, did not. Moreover, derivatives a and d also enhanced anti-LPS PFC. From experiments establishing minimum effective doses for anti-SRBC PFC in mice, one mg/kg was optimum for BALB/c mice. The effect of the drug on antibody formation against heterologous erythrocytes was nonspecific because treated mice had greatly depressed PFC responses against both sheep and rabbit erythrocytes. The phenotypic effect of this drug as judged by PFC against T-dependent or T-independent antigen was not identified. However, it was suggested that the purified derivatives SSa and d stimulated both T- and B-cells. The possible mechanism of effect against immunocompotent cells is discussed.