1H-1H COSY, 1H-1H correlation spectroscopy; ANOVA, Analysis of variance; Akt, Protein kinase B; CCK-8, Cell counting kit-8; D2O, Deuterium oxide; DCFH-DA, 2',7'-Dichlorofluorescein diacetate; DEPT, Distortionless enhancement by polarization transfer; DMEM, Dulbecco's modified Eagle's medium; DPBS, Dulbecco's phosphate-buffered saline; ELISA, Enzyme-linked immunosorbent assay; ERK, Extracellular signal-regulated kinase; FT-IR, Fourier transform infrared spectroscopy; GC-MS, Gas chromatography-mass spectrometry; HMBC, Heteronuclear multiple bond correlation; HPGPC, High-performance gel permeation chromatography; HPLC, High performance liquid chromatography; HSQC, Heteronuclear single quantum correlation; Heteropolysaccharide; IL-6, Interleukin-6; Immunomodulatory activity; IκBα, I kappa B alpha; JNK, c-Jun N-terminal kinase; LPS, Lipopolysaccharides; MAPKs, Mitogen-activated protein kinase; MCP-1, Monocyte chemoattractant protein-1; Mw, Weight average molecular weight; NF-κB, Nuclear factor-kappa B; NMR, Nuclear magnetic resonance; NO, Nitric oxide; PI3K, Phosphatidylinositol-3-kinase; PMP, 1-Phenyl-3-methyl-5-pyrazolone; RIPA, Radioimmunoprecipitation assay; ROS, Reactive oxygen species; RT-PCR, Reverse transcription-polymerase chain reaction; Structural characterization; Suillus granulatus; TLR2, Toll-like receptor 2; TLR4, Toll-like receptor 4; TNF-α, Tumor necrosis factor-α; iNOS, Inducible nitric oxide synthase