Polysaccharide K (PSK)

Polysaccharide-K is a protein-bound polysaccharide, which is used as an anticancer immunologic adjuvant in some countries. PSK is isolated from the fruitbody of Trametes versicolor. PSK was effective against various allogeneic and syngeneic animal tumors and has been given orally to cancer patients. Various suppressed or enhanced immune responses of tumor-bearing animals were restored to normal levels by the administration of PSK in the tumor models tested. The killer T cell activity was augmented in tumor-bearing mice by intraperitoneal or oral administration of PSK, and there was correlation between the PSK associated antitumor effect and the killer T cell activity. It was found that PSK competed with immunosuppressive substances isolated from tumor-bearing mice and that the intestinal immune system appeared to be modulated by oral administration of PSK.