Figure 2.

Possible inhibitory mechanisms result in immune escape. The liver microenvironment is enriched with various cells that can inhibit the T cell responses. Abnormal PD-1, Tim-3, and other negative signaling pathways probably result in the T cell exhaustion. MDSCs and Tregs could be a great source of arginase and suppress T cell responses through arginase and secreting several immune-modulatory cytokines such as TGF-β1 and IL-10. In addition, CD24⁺ Breg cells may suppress T cell function by IL-10. Furthermore, HBV-specific CD8⁺ T cells could be lysed by activated NK cells via a contact-dependent manner (for example, TRAIL/TRAIL-R). MDSC, Myeloid-derived suppressor cells; TRAIL, tumor necrosis factor-related apoptosis-inducing ligand.