Effects of a pectic polysaccharide from a medicinal herb, the roots of Bupleurum falcatum L. on interleukin 6 production of murine B cells and B celllines

The effect of T-cell-independent B cell mitogen, a pectic polysaccharide, b upleuran 2IIc, from a medicinal herb, the roots of Bupleurum falcatum L. on interleukin 6 (IL-6) production of murine B cells and B cell lines was inv estigated in order to clarify the mechanism of enhanced immunoglobulin (Ig) secretion from B cells. Bupleuran 2IIc enhanced IgM secretion from highly purified murine normal B cells. When normal B cells from murine spleen were cultured with bupleuran 2IIc in the presence of anti-IL-6 neutralizing ant ibody, the enhanced IgM secretion by bupleuran 2IIc was reduced. When B cel ls were stimulated with bupleuran 2IIc, their IL-6 secretion and the transc ription of IL-6 mRNA were enhanced. The enhanced IL-6 secretion by bupleura n 2IIc was also observed in B cell line, Y16 cell. When bupleuran 2IIc was digested with endo-alpha-(1 --> 4)-D-polygalacturonase, the resulting enzym e resistant carbohydrate portion, "ramified" region (PG-1) composed of rham nogalacturonan core containing neutral sugar side chains showed potent IL-6 secretion-enhancing activity. These results suggest that the "ramified" re gion of bupleuran 2IIc stimulates the secretion of IL-6 as the active site, and the resulting IL-6 may partially contribute the enhancement of IgM sec retion as an autocrine and/or paracrine mechanism. (C) 2000 Elsevier Scienc e B.V. All rights reserved.