Recent progress in immunopharmacology and therapeutic effects of polysaccharides.

Lentinan, a (1----3)-beta-D-glucan with (1----6)-beta-D-glucopyranoside branches and its related polysaccharides have marked antitumour activity in allogeneic, syngeneic and autochthonous primary hosts, suppress chemical and viral oncogenesis, and prevent cancer recurrence or metastasis after surgery. Results of the clinical application of lentinan have proven prolongation of life-span of the patients with advanced and recurrent stomach, colorectal and breast cancer with only little toxic side effect. These polysaccharides also increase host resistance to various kinds of bacterial, viral and parasitic infections including AIDS. Lentinan appears to represent Host Defence Potentiators (HDPs), which can restore or augment the ability of responsiveness of the host to lympho-cytokines or other intrinsic bioactive factors through maturation, differentiation or proliferation of the important cells for host defence mechanisms. That is, HDPs might make the physiological constitution highly cancer and infection-resistant, which may be a concept in Oriental Medicine, the fundamental principle of which is to regulate homeostasis of the whole body and to bring the diseased person to his normal state. HDPs such as lentinan are the most appropriate drugs to prevent cancer recurrence, or the manifestation of AIDS symptoms in HIV carriers.