Carbohydrate-based vaccines have shown therapeutic efficacy for infectious disease and cancer. The mushroom Ganoderma lucidum (Reishi) containing complex polysaccharides has been used as antitumor supplement, but the mechanism of immune response has rarely been studied. Here, we show that the mice immunized with a L-fucose (Fuc)-enriched Reishi polysaccharide fraction (designated as FMS) induce antibodies against murine Lewis lung carcinoma cells, with increased antibody-mediated cytotoxicity and reduced production of tumor-associated inflammatory mediators (in particular, monocyte chemoattractant protein-1). The mice showed a significant increase in the peritoneal B1 B-cell population, suggesting FMS-mediated anti-glycan IgM production. Furthermore, the glycan microarray analysis of FMS-induced antisera displayed a high specificity toward tumor-associated glycans, with the antigenic structure located in the nonreducing termini (i.e., Fucα1-2Galβ1-3GalNAc-R, where Gal, GalNAc, and R represent, respectively, Dgalactose, D-N-acetyl galactosamine, and reducing end), typically found in Globo H and related tumor antigens. The composition of FMS contains mainly the backbone of 1,4-mannan and 1,6-α-galactan and through the Fucα1-2Gal, Fucα1-3/4Man, Fucα1-4Xyl, and Fucα1-2Fuc linkages (where Man and Xyl represent D-mannose and D-xylose, respectively), underlying the molecular basis of the FMSinduced IgM antibodies against tumor-specific glycans. mushroom polysaccharide | antitumor activity | anti-Globo H antibody V arious forms of herbal medicine polysaccharides have become valuable as health supplements worldwide (1, 2), suggesting that administration of such polysaccharides may improve innate immunity in vivo. The underlying molecular mechanisms, however, still remain ambiguous. Aberrant terminal fucosylation as well as sialylation in tumor-associated glycans is one of several glycosylation events important in cancer progression (3, 4), and such unusual glycans have recently been used for the development of anticancer vaccines (5-7). As an example, the Globo H-based glycoconjugate vaccines are currently undergoing large-scale clinical trials and have shown promise in therapeutic treatment (8, 9). Studies on the immune response to pathogenic microorganisms (such as Haemophilus influenza type B and Streptococcus pneumonia) have demonstrated that polysaccharides containing repeating antigenic units are generally T cell-independent (TI) (10, 11). Furthermore, recent findings revealed that specific B-cell subsets could establish memory for providing specific Ig synthesis in response to TI-associated polysaccharides (12)(13)(14). In an attempt to understand the biological significance of polysaccharides derived from natural sources, we previously isolated and characterized a crude extract fraction of water-soluble and L-fucose (Fuc)-containing polysaccharides (F3) from Ganoderma lucidum (Reishi) (a mushroom that has been long used as a herb medicine) (15). F3 has since been shown essential for regulation of cytokine network...
