Polysaccharides from pectinase digests of green tea enhances host immune defence through toll-like receptor 4

To develop new immunostimulatory ingredients, green tea polysaccharides were obtained by pectinase-assisted extraction. The present study investigated the immune stimulating and protective ability of polysaccharides from pectinase digests of green tea (PPGT) against infectious disease and the mechanisms involved. Macrophages stimulated with PPGT exhibited dose-dependent increases in nitric oxide, tumour necrosis factor-α (TNF-α) production and phagocytosis. PPGT increased phosphorylation of mitogen-activated protein (MAP) kinase, nuclear factor-kappaB (NFκB) and signal transducers and activators of transcription (STATs) through toll-like receptor 4 (TLR4) activation. The survival of mice infected with a lethal dose (1 × 10 7 CFU) of S. typhimurium was significantly extended by PPGT administration. Furthermore, PPGT induced production of cytokines (interleukin-12, interferon-γ, and TNF-α) in mice infected with a sub-lethal dose (1 × 10 5 CFU) of S. typhimurium. Furthermore, PPGT was significantly promoted natural killer cell and cytotoxic T lymphocyte activity. The above results lead to conclude that PPGT have a potent immune stimulating effect on immune cells via TLR4 pathway.