1, 17 However, its detailed function on CD8+ T-cells during chronic viral infection in humans has remained unknown. Therefore, we addressed CD244 as a potential inhibitory
molecule in chronic HBV infection and analyzed its expression and functional influence on impaired virus-specific CD8+ T-cells. Our results suggest that CD244 can act as an inhibitory receptor on HBV-specific CD8+ T-cells, which is supported by at least four important findings: First, CD244 was higher on virus-specific CD8+ T-cells in chronic HBV compared to total CD8+ T-cells, which Erismodegib in vivo could be interpreted as a specific up-regulation. Liver-derived virus-specific and total CD8+ T-cells expressed high amounts of CD244, indicating an up-regulation at the side of viral replication. Second, viral clearance was associated with low expression of CD244. Third, chronically
infected HBV patients were characterized by high coexpression of CD244 with PD-1 in the peripheral blood and the liver. click here Fourth, CD244 blockade recovered T-cell proliferation, cytokine production, and cytotoxicity in chronic infection but not in acute patients, resolvers, and EBV infection. These observations indicate that CD244 contributes to T-cell dysfunction and can act in concert with other inhibitory molecules. In our study, chronically infected HBV patients are characterized by high levels of CD244 in comparison to acutely infected individuals and resolvers. In this context, Peritt et al.18 could show that CD244 expression increases in HIV patients with disease progression, which confirmed
our observation of CD244 up-regulation during chronic HBV infection. Notably, CD244 was highly coexpressed with PD-1 in the peripheral blood and the liver of chronically infected patients but not with activation markers. These characteristics underline the inhibitory function of CD244 in HBV persistence and are in line with recently published data in mice.1, 17 A distinct up-regulation of inhibitory molecules such as PD-1 on intrahepatic CD8+ T-cells reflects the specific immunological features in the chronically infected liver as the side of viral replication.19 We therefore selleck investigated CD244 on liver-derived virus-specific CD8+ T-cells and could show that CD244 was up-regulated on intrahepatic CD8+ T-cells with high PD-1 coexpression. Higher CD244 expression in the liver could be due to higher levels of antigen or a different cytokine milieu in the inflamed liver tissue. The inhibitory function of CD244 was suggested to be mainly dependent on the receptor per cell amount and the presence of SAP.20 Thus, low or intermediate expression was suggested to deliver positive signaling, whereas high expression in the presence of low SAP mediates negative signaling.6 The data collected in our study support these findings and are consistent with an inhibitory function of CD244 on CD244highCD8+ T-cells.