Biomedical Research Laboratories, Kureha Chemical Industries Co., Ltd., Tokyo, Japan.
PSK (Krestin) is a protein-bound polysaccharide isolated from cultured mycelia of Coriolus versicolor in basidiomycetes. PSK is a biological response modifier which possesses unique characteristics. We investigated the effects of PSK on the immune response of aged C57BL/6 mice bearing a syngeneic transplantable tumor adenocarcinoma 755. (a) In C57BL/6 mice, the delayed foot pad reaction against sheep erythrocytes and resistance to syngeneic tumor challenge reached a peak when the mice were at 30 weeks of age, and decreased at 50-60 weeks of age. The serum of normal mice exerts a modifying effect on blastogenesis of lymphocytes to phytohemagglutinin. The positive effect reached a peak at 30 weeks of age, and thereafter declined with age. (b) When adenocarcinoma 755 was inoculated to C57BL/6 mice at 10-, 30- and 60-weeks of age, immune responses were depressed in 10-week-old and 60-week-old mice. PSK prevented such depression. However, in 30-week-old mice, tumor-induced suppression was slight, and administration of PSK to them increased proportion of mice which did not develop a tumor. (c) In 60-week-old tumor-bearing mice, the antitumor effects was increased with a combination of PSK and adoptive transfer of spleen cells from 10-week-old normal mice. The immune responses of mice, which change with the progress of age, are depressed by tumor burden. The administration of PSK to aged mice is effective to restore immune responses from tumor-induced suppression.
PMID: 3430562 [PubMed – indexed for MEDLINE]