Potentiation of host-mediated antitumor activity in mice by .BETA.-glucan obtained from Grifola frondosa (maitake)

A polysaccharide (3-branched β-1, 6-glucan MT-2) extracted from fruit bodies of Grifola frondosa (maitake) showed an antitumor effect against mouse syngeneic tumors (MM-46 carcinoma and IMC-carcinoma). It is not only directly activates various effector cells (macrophages, natural killer cells, killer T cells, etc.) to attack tumor cells, but also potentiates the activities of various mediators including lymphokines and interleukin-1. Thus, it acts to potentiate cellular functions and at the same time to prevent a decrease of immune functions of the tumor-bearing host.