Polysaccharides PES isolated from a common Oriental herb Acanthopanax senticosus were found to have a wide spectrum of immunomodulatory activities on experimental animals. The potential usefulness of these polysaccharides is suggested in the observations that PES inhibited transplanted tumor growths and ameliorated toxicities of the toxic substances in experimental animals. Of most interest is the observations that they suppressed human TB propagation in mice and guinea pigs, as evaluated by lymph node responses and OT skin tests in the guinea pig model, and the quantitation of the TB in the lungs in the mouse model.