The effect of a protein-bound polysaccharide on T cell subsets of peripheral venous blood and thoracic duct lymph.

To investigate the effect of a protein-polysaccharide preparation, PSK, on immune system function, the ratios of peripheral venous blood and thoracic duct lymphocyte subsets were determined in 6-week-old male SPF Wistar-Imamichi strain rats maintained on a diet containing 2% PSK ad libitum. Peripheral blood and thoracic duct lymph specimens were obtained from pretreatment, 4- and 8-week PSK-treated, and period-matched control groups of rats. The lymphocyte count and percentages of helper/inducer and suppressor/cytotoxic T cells were determined with a laser flow-cytometry system using monoclonal antibodies W3/13, W3/25 and OX8. Compared with the controls, the PSK-treated group showed significantly lower total T cell and helper/inducer T cell counts in the peripheral blood, but showed no difference in the suppressor/cytotoxic T cell count. However, in the thoracic duct, there were significantly increased total T cell and helper/inducer T cell counts, but no difference in suppressor/cytotoxic T cell counts compared with the controls. These data appear to indicate a significant activity of oral PSK, resulting in modulation of lymphocyte distribution in the body by facilitation of the transition of circulating T lymphocytes, especially helper/inducer T cells, into the lymph.