The effect of PS-K, a protein bound polysaccharide, on immune responses against allogeneic antigens.

A single dose of PS-K administered to C57B1/6J mice after immunization augmented both the humoral and cellular allogeneic responses against P815 tumor cells. PS-K addition to primary alloantigen sensitization cultures (C57B1/6J spleen cells against X-irradiated P815 cells) resulted in augmented 3H-thymidine uptake and cell mediated cytolytic activity. Ten daily administrations of PS-K to DBA/2J mice after implantation of a mammary tumor of DBA/2HaDD origin results in increased tumor regression and prolonged survival of the mice. PS-K addition to human mixed lymphocyte cultures caused an augmentation of both cell mediated cytolytic activity and 3H thymidine uptake. The dose dependence of the PS-K effects were described by a bell shaped curve and PS-K did not appear to affect the day of peak development of the various responses. The effects were consistently greater if PS-K was administered at the same time or after antigen presentation. Thus, the immunoaugmenting effects induced by PS-K were similar in each model system tested.