Key Points
Lentinula edodes, Grifola frondosa, Pleurotus cornucopiae, Pholiota nameko, and many other kinds of edible mushrooms have shown their potent and unique immunomodulating activities. It has mainly been recognized that their activities result from the action of their polysaccharides or polysaccharide–protein complexes. The polysaccharides appear to stimulate the human immune response and to be effective in preventing immunodeficiency diseases via activation of cytokine networks. In this chapter, these properties of the immunomodulating polysaccharides from L. edodes, G. frondosa, P. nameko, P. cornucopiae, and others are described.