Inhibitory function of Tregs via soluble FGL2 in chronic hepatitis B

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Summary

CD4+CD25+CD127dim/− regulatory T cells (Tregs) have been implicated in suppressing T cell immune responses to hepatitis B virus (HBV), but the inhibition mechanism has not being clear yet. This study investigated the effects of soluble FGL2 (sFGL2) secreted by Tregs on immune suppression in chronic HBV-infected patients. We verified that sFGL2 protein and mRNA were highly expressed in Tregs. The separated Tregs by using magnetic beads from peripheral blood mononuclear cells (PBMCs) in 20 patients with chronic hepatitis B were co-cultured with PBMCs at a ratio of 1:3 with anti-CD3 stimulating antibody or FGL2 blocking antibody. The proliferation index of CD8+T cells after blocking FGL2 was higher than that in blank group (3.58±0.18 vs. 3.28±0.17, P=0.034) in 18 of 20 samples, and lower than that in CD3 stimulation group (3.82±0.19, P=0.026) in 16 of 20 samples. The IFN-γ secreted in the mixed culture in the absence of Tregs was higher than that in the culture in the presence of Tregs, but it could be abolished by FGL2 blocking antibody. These results suggest that sFGL2 protein secreted by Tregs suppresses the proliferation and function of CD8+ T cells in chronic hepatitis B.

This project was supported by National 973 Project in Viral Hepatitis, China (MOST, No. 2007CB512900).