ENHANCEMENT OF ANTITUMOR CYTOTOXICITY OF HEPATIC LYMPHOCYTES BY ORAL-ADMINISTRATION OF PSK

We have studied the effects of oral administration of a biological res ponse modifier (BRM), PSK, on hepatic lymphocytes. Many PSK positive c ells were observed in the liver by anti-PSK antibody staining. Flow cy tometric analysis revealed an increase in the number of OX8 (CD8) posi tive cells in the nonparenchymal nonadherent liver cells (NPNALCs) whi ch were isolated from the liver enzymatically digested by perfusion wi th collagenase. NPNALCs were fractionated by discontinuous density gra dient centrifugation, and the number and cytotoxic activity of these c ells were examined in each fraction. Although the yield of lymphocytes in each fraction was not significantly increased by the oral administ ration of PSK, the natural killer (NK) activity was markedly enhanced in low density fractions. The present findings suggest that oral admin istration of PSK is effective for prevention of liver metastasis throu gh the augmentation of organ-associated NK activity.