Regulatory Effect of Astragalus Polysaccharides on Intestinal Intraepithelial γδT Cells of Tumor Bearing Mice

Astragalus polysaccharides (APS) possess multiple immunomodulatory activities. Due to its high molecular weight, orally administration of APS is not easily absorbed into the blood stream, and how APS exerts its capacity in vivo is still not well elucidated. We assume that enteric mucosal immune response might trigger the immune regulation of APS, and our previous studies demonstrated that APS had regulatory activity on intraepithelial lymphocytes (IELs). Therefore, this study aimed to investigate the functions of APS on intestinal intraepithelial gamma delta T cells, a major subset in IELs and an essential component of maintaining homeostasis and immune regulation in enteric mucosa. Results showed that APS could promote proliferation and function of intestinal intraepithelial gamma delta T cells in vitro, the IFN-gamma, FasL and GrB mRNA levels in gamma delta T cells were all significantly increased. Moreover, APS also improved the activity of intestinal intraepithelial gamma delta T cells in vivo, as cytokines production and cytotoxicity of gamma delta T cells were all remarkably improved in tumor-bearing mice treated with APS. In addition, the levels of TNF-alpha and IFN-gamma were significantly increased, whereas the levels of IL-10 and TGF-beta were significantly decreased in tumor-bearing mice treated with APS. In conclusion, this study demonstrated that APS could improve proliferation and function of intestinal intraepithelial gamma delta T cells, which might an important pathway for immunomodulation of APS in cancer therapy.