A polysaccharide from Sargassum fusiforme protects against immunosuppression in cyclophosphamide-treated mice

► A water-soluble polysaccharide (SFPS) was isolated and purified from Sargassum fusiforme. ► Structural characterization of SFPS was investigated. ► SFPS stimulated proliferation and cytokines secretion of murine splenic lymphocytes. ► SFPS markedly increased the phagocytic rates and cytokines secretion of peritoneal macrophages. ► SFPS had immunostimulatory effects against cyclophosphamide-induced immunosuppression.