[Effect of PSK on the recovery of macrophage function and T cell-mediated immunity in tumor-bearing mice].

The effect of PSK on the depressed bactericidal activity of macrophages and delayed-type hypersensitivity (DTH) to Listeria monocytogenes in BALB/c mice bearing transplantable Meth A fibrosarcoma was studied. In tumor-bearing mice pretreated with PSK, L. monocytogenes was cleared rapidly from the circulating blood and bacterial growth in the liver was inhibited effectively in the early phase of infection. This resistance to the infection could be transferred with peritoneal exudate cells (PEC) but not with non-adherent PE cells of PSK-treated mice. In the early phase of infection, tumor-bearing mice developed a lower level of DTH to L. monocytogenes than did nongrafted control mice. However, the control levels of DTH could be obtained by pretreatment of tumor-bearing mice with PSK. These results suggest that the restoration of resistance to L. monocytogenes in tumor-bearing mice by PSK may be ascribed to both prevention of depression or activation of macrophage function and prevention of depression of T cell-mediated immunity.