AbstractThe effects of oral administration of antitumor polysaccharide SPR-901 (RBS), anα-1,3 branchedα-1,6 glucan, on concanavalin A (Con A)-induced interleukin 2 (IL-2) production of splenocytes were studied. The augmentation effect on Con A-induced IL-2 production was evident when more than 30 mg/kg of SPR-901 was administered orally to mice. On the other hand, oral administration of B512 dextran, an analogousα-1,6 glucan, did not show any augmentation effects on IL-2 production. The augmentation effect of SPR-901 on IL-2 production seemed to be mediated mainly by macrophages stimulated with SPR-901.