Immunomodulatory Effect of the Polysaccharide-Rich Fraction from Sclerotium of Medicinal Mushroom Poria cocos F.A. Wolf (Aphyllophoromycetideae) on Balb/c Mice

Dried sclerotia of medicinal mushroom Poria cocos F.A.Wolf were extracted with cold water. The extract was precipitated by ethanol and then lyophilized to obtain the polysaccharide-rich fraction (PRF). The immunomodulatory effect of the PRF on Balb/c mice was investigated. Oral administration of the PRF did not affect the growth of healthy mice. The relative proliferation ratio of phytohemagglutinin-stimulated splenocytes increased significantly, whereas the natural killer cell activity and numbers of T, T helper, T cytotoxic (Tc), and B cells remained unchanged, excluding the occurrence of a nonspecific immune-response. Some other healthy mice were immunized with ovalbumin (OVA) to conduct specific immune-response experiments. Oral administration of PRF at 200 mg/kg bw to the immunized mice increased the Tc percentage among splenocytes but reduced anti-OVA immunoglobulin G and M levels significantly, indicating that PRF could modulate the specific immune response of Balb/c mice and that the modulation is via the activation of T cells.