Effects of the herbal medicine "Sai-rei-to" on in vitro interferon-gamma production of peripheral blood mononuclear cells.

The herbal medicine "Sai-rei-to" has been used in the treatment of swellings and edemas for about 3000 years in China. Recently, this drug has been prescribed as an adjuvant in the treatment of rheumatoid arthritis (RA) among Japan's western medicine doctors. It is thought to possess regulatory effects on the immune system, although its mode of action is not yet fully described. In the present in vitro study, we at first induced interferon-gamma (IFN-gamma) in the cultures of peripheral blood mononuclear cells of healthy volunteers by adding pokeweed mitogen (PWM), phytohemagglutinin (PHA), recombinant interleukin-2 (IL-2), or control medium. We then added "Sai-rei-to" to these cultures and investigated the effects of this drug on IFN-gamma production levels. The results demonstrated that "Sai-rei-to" had 2 different effects: (i) it inhibited the IFN-gamma production in cultures with PWM or PHA (which induced large volumes of IFN-gamma), and (ii) it increased IFN-gamma production in the cultures with IL-2 (IL-2 induced only small volumes of IFN-gamma). These findings indicate that "Sai-rei-to" possesses regulatory effects on the IFN-gamma production. IFN-gamma is an important cytokine in the immune system, and it has also attracted attention as a factor related to the pathogeneses of RA. Therefore, concomitant administration of such a medicine which can appropriately control IFN-gamma production in vivo could be beneficial for RA patients from the immunological viewpoint. Clinical experience in the past has shown that "Sai-rei-to" has a very low incidence of side effects, and can be administered orally for long periods. We expect that concomitant administration of "Sai-rei-to" with current therapy could be clinically useful in the management of RA patients.