Effect of PSK on interferon production in tumor-bearing mice.

The effect of PSK on the depressed interferon (IF) production in tumor-bearing mice was studied. In tumor-bearing mice, in vitro IF production by spleen cells treated with polyinosinic-polycytidylic acid (poly I:C) was remarkably inhibited. However, these inhibitions were prevented by the intraperitoneal (ip) administration of PSK. Mice were inoculated intravenously (iv) with poly I:C-treated spleen cells, administered with PSK ip at 3 days after the tumor inoculation. When PSK was not given, poly I:C-treated spleen cells did not show an inhibitory effect on tumor growth. In mice given PSK ip, poly I:C-treated spleen cells exerted slightly inhibiting effects on tumor growth. These results suggest that PSK prevented such a modulation in tumor-bearing mice.