Structural characterization of a polysaccharide from Trametes sanguinea Lloyd with immune-enhancing activity via activation of TLR4

A bioactive polysaccharide (TS2-2A) with a molecular weight of 15 kDa was isolated from Trametes sanguinea Lloyd, a medicinal food homologous fungus, by water extraction-alcohol precipitation and chromatographic separation. NMR analysis of polysaccharide and MS/MS analysis of its oligosaccharide indicated that TS2-2A featured a novel straight chain with a backbone of 1,3-α-d-glucopyranose and 1,4-β-d-glucopyranose at a molar ratio of 1:4. Moreover, TS2-2A, recognized by Toll-like receptor 4 (TLR4), stimulated RAW 264.7 macrophages to release related cytokines and contributed to immune-enhancing effects. Briefly, with remarkable immune-enhancing activity and noncytotoxicity, TS2-2A was proposed to be a potential immune enhancer for supplementing drugs or functional foods.