Effect of a protein bound polysaccharide (PS-K) on tumor development and infections in splenectomized rats and mice

Daily oral administration of PS-K, an immunomodulating agent, was found to improve survival rate in tumor bearing mice and rats and to decrease susceptibility to infection in mice. Surprisingly, splenectomized tumor bearing rats and mice responded better to PS-K treatment as measured by survival rate, tumor size and immunosuppressive properties of serum. The mechanism of PS-K antitumor activity in both experimental systems might be due to the alteration of splenic immune suppressive mechanisms during tumor growth in the host. On the other hand, host resistance to acute infection was found to be less dependent upon the presence or absence of spleen suggesting a different mechanism of PS-K activity in acute infectious disease.