[Possible zymosan stimulation of the immune response of BALB/c mice to sheep erythrocytes and tumor target cells].

Zymosan and its combinations with cyclophosphamide were tested for their effect on various immune responses. Zymosan alone had only minor effect on the cytotoxicity of lymphocytes to allogeneic and syngeneic tumour cells but significantly stimulated delayed-type hypersensitivity response, rosette formation and plaque forming cell response to sheep red blood cells in normal mice. Zymosan diminished immunosuppressive action of cyclophosphamide on the plaque and rosette formations and nonspecific allogeneic lysis of target cells by lymph node lymphocytes. Delayed-type hypersensitivity skin reaction and syngeneic T-killer cell activity increased significantly after the procedure of combination therapy. Lymphocyte stimulation action by the polysaccharide depended on the injection schedule used. Preliminary injection of zymosan was an optimal condition for enhancement of the cellular immune response.