A novel type of B-cell mitogen isolated from juzen-taiho-to (TJ-48), a Japanese traditional medicine.

Juzen-taiho-to (TJ-48), a Japanese traditional medicine, is known to have various immunological activities including the induction of B-cell proliferation. We investigated the properties of the pectic polysaccharide fraction of TJ-48 (F-5-2) which is most active in the proliferation of spleen cells. To an extent equal to that of TJ-48, F-5-2 induced the proliferation of B-cells, particularly those holding both sIgM and sIgD. The proliferation induced by F-5-2 was T-cell independent and macrophage dependent. The macrophages could be substituted for a soluble factor(s) secreted from the macrophages but not for IL-1. Generally, B-cell mitogens are known to induce the proliferation of B-cells and subsequently differentiation into plasma cells. However, although F-5-2 induced the B-cell differentiation, it arrested their development in the intermediate stage of the B-cell differentiation. The B-cells induced by F-5-2 produced IgM antibody in response to IL-6 and an antigen (SRBC) but not IgG antibody. F-5-2 induced the expression of IL-6R not only on IgM+ and IgG+ B-cells but also on IgD+ B-cells. These results suggest that F-5-2 is a new type of B-cell mitogen.