Cytokine-related immunomodulating activities of an anti-tumor glucan, sizofiran (SPG).

Sizofiran (SPG), antitumor glucan isolated from Shizophyllum commune Fries was examined for its effect on the lymphoid cell functions related to production of cytokines or responses to these cytokines. Lymphoid cells were isolated from mice injected intramuscularly with SPG and then examined for responses to the cytokines, interleukin (IL)-1, IL-2 or IL-3 or the production of these cytokines in response to the stimuli of mitogens, and the following results were obtained. (1) The thymocytes isolated from the SPG-treated mice proliferated in response to stimulation by IL-1 in combination with concanavalin A (ConA) to a much greater degree than was the case with control mice. (2) When the spleen cells isolated from the mice were cultured with IL-2 or IL-3, augmented proliferative response was observed in either case. (3) Peritoneal macrophages, when stimulated with lipopolysaccharide (LPS), produced IL-1 to the levels much higher than those of control mice. (4) When the spleen cells were cultured with ConA, augmented production of IL-2 and IL-3 were also observed. (5) In addition, we found that activity stimulating the bone marrow cells in vitro culture was reproducibly detected in the serum of mice 20 h after injection with SPG. Overall, these results indicate that SPG injected into mice has the ability to produce the bone marrow stimulating factor(s) in the serum early after injection and stimulate lymphoid cells to become much more responsive to various stimuli such as lectins or cytokines.