Glycoproteins and Polysaccharides are the Main Class of Active Constituents Required for Lymphocyte Stimulation and Antigen-Specific Immune Response Induction by Traditional Medicinal Herbal Plants

Traditional herbal remedies stimulate and modulate the immune system, and it is thought that their glycoproteins and polysaccharides are responsible for this activity. We prepared crude water, protein, and polysaccharide extracts from Atractylodes macrocephala Koidz, Helianthus annuus L., Scutellaria barbata D. Don, and Hedyotis diffusa Willd, respectively, and compared their immune-stimulating activities in vitro and in vivo. All protein and polysaccharide samples of the plants led to greater lymphocyte proliferation and TNF-α and IL-6 production in cultured splenocytes than did the crude water extracts at the same concentrations tested. In addition, the protein and polysaccharide samples did not contain lectin- or lipopolysaccharide-like molecules, so glycoproteins were deduced to be responsible for the lymphocyte stimulation. Oral administration with each of the samples enhanced the hen egg-white lysozyme (HEL)-specific humoral immune and lymphocyte proliferative responses in HEL low-responder C57BL/6 mice. Splenocytes from the mice fed the samples showed significantly greater increases in the level of IFN-γ, but not IL-4, after stimulation with HEL compared with that from the untreated control. However, higher increases in HEL-specific IgG1, IgG2b, and IgG3 rather than IgG2a were found in the mice fed the samples. These results indicate that the sample-mediated enhancement of anti-HEL-specific humoral immune responses was due to the stimulation of B lymphocytes rather than a selective priming of helper T cell populations. Collectively, we suggest that glycoproteins and/or polysaccharides of traditional herbal remedies enhance cellular and humoral immune response induction and thus could be useful for patients who need enhanced immune function.