The effect of a biological response modifier, PSK, on the intestinal immune system in tumor-bearing mice.

We have previously shown that oral administration of PSK not only exerts antitumor activity, but also restores immune response in tumor-bearing mice. In order to analyze the immunomodulative effect of PSK, we investigated the effects of oral PSK on the intestinal immune systems in ICR mice bearing sarcoma 180. Oral administration of PSK increased the number of Peyer's patches that developed relatively well, and led to recovered mitogenic response of lymphocytes from gut-associated lymphatic tissue and responsiveness to oral preimmunization with SRBC in tumor-bearing mice. These results suggest that PSK modulates the immunity in intestinal tract of tumor-bearing mice.