Regulation of maturation and function of dendritic cells by tea glycoprotein

Tea glycoprotein (TGP) is a glycoconjugate purified from the leaves of green tea (Camellia sinensis). The objective of this study was to evaluate the immunomodulatory effects of TGP on dendritic cells. Murine bone marrow cells were cultured with recombinant mouse (rm)GM-CSF and rmIL-4 for 6 days followed by another 2 days in the presence of TGP or lipopolysaccharide (LPS). The results showed that TGP did not have significant inhibition on cell proliferation and apoptosis. Compared with untreated cells, dendritic cells treated with TGP (50 μg/ml) expressed higher levels of MHC class II molecules and major co-stimulatory molecules such as CD 86, CD 80 and CD 40. However, the endocytic activity was impaired markedly. TGP could enhance the secretion of IL-12p70, but inhibit IL-10 and NO secretion. The activation of antigen-presenting ability and the lymphocyte proliferation of mixed lymphocyte reaction by dendritic cells was also enhanced after treatment with TGP. In addition, an enhanced expression of CCR7 mRNA of dendritic cells treated with TGP was similar to dendritic cells treated with LPS. Taken together, TGP was capable of promoting both phenotypic and functional maturation of murine bone marrow-derived dendritic cells in vitro, which promises the potential clinical application of TGP.