Kakkon-to, a traditional herbal medicine (
Kampo formula), has been used historically in China and Japan for the treatment of
infectious diseases such as
influenza and the
common cold. However, the
biological mechanism of its therapeutic action has not yet been elucidated. In this study, we investigated the immunological function of
Kakkon-to and found that the high molecular weight fraction of the extract activated macrophages in vitro. This fraction was found to be composed primarily of saccharides and in vitro intensively stimulated mouse peritoneal macrophages that produce Th1 inflammatory
cytokines such as
tumor necrosis factor α (
TNFalpha),
interleukin-1beta (IL-1beta),
interferon-gamma (IFN-gamma), and
interleukin-6 (IL-6). The fraction did not activate macrophages from C3H/HeJ lacking
Toll-like receptor 4 (TLR4) or MyD88-deficient mice, indicating that macrophage activation by the fraction was mediated by TLR4. The route of administration of the fraction into mice regulated the kinetics of
TNFalpha production in immune organs.
Intravenous administration induced
TNFalpha production in the four target organs of spleen, liver, lung, and Peyers patch; however, the most abundant production occurred in the liver and peaked at 30-60 min post administration. Peritoneal administration induced similar kinetics but the most abundant production occurred in the spleen. In contrast,
oral administration induced
TNFalpha production in the liver, lung, and Peyers patch, but not in the spleen. Although liver and lung are
TNFalpha-abundant organs, production peaks in these organs occurred later than in Peyers patch. We also found that the fraction induced antibody production as an adjuvant against a specific
antigen ovalbumin (OVA) when administered simultaneously and subcutaneously in a dose-dependent manner. Interestingly, the fraction induced
IgG-
class antibody in response to low doses of the
antigen, which induced only
IgM-
class antibody when administered alone, suggesting that the fraction induces a class switch of
immunoglobulin as an adjuvant in vivo. The high molecular weight fraction of
Kakkon-to extract could be applicable as a potent immunostimulating
drug and adjuvant.