Possible involvement of suppression of Th2 differentiation in the anti-allergic effect of Sho-seiryu-to in mice.

The clinical effectiveness of the Kampo medicine Sho-seiryu-to (SST) has recently been demonstrated in a double-blind randomized study of allergic asthma and rhinitis. We investigated the effect of SST on a type 1 allergic model in mice. Ovalbumin (OVA)-induced sneezing and the total and OVA-specific IgE levels were significantly suppressed with SST at 1.0 g/kg, but that of OVA-specific IgG(2a) was not. In the splenocytes isolated from SST-administered mice, OVA-induced interleukin (IL)-4 production decreased while interferon (IFN)-gamma production was not. The co-culture experiments using purified CD4(+)T cells and antigen-presenting cells (APCs) suggested that SST influenced both cell types. Flow-cytometric analysis showed that SST suppressed the number of IL-4 producing CD4(+)T cells but not the number of IFN-gamma producing CD4(+)T cells. The CD86(+) major histocompatibility complex class II(+) (MHC II)(+) cells and CD28(+)CD4(+)T cells were decreased by SST treatment, while CD80(+)MHC II(+) cells, CD40(+)MHC II(+) cells and CD154(+)CD4(+)T cells showed no change. These data suggested that SST may suppress IL-4 production in CD4(+)T cells via influencing CD28-CD86 interaction. In addition to the previously reported inhibitory activity on histamine release, suppression of Th2 differentiation at the stage of APC-CD4(+)T cell interaction may be involved in the anti-allergic effects of SST.