Interestingly, the numbers of these TNF-expressing CD8+ T cells were further enhanced by Treg depletion (Fig. 3B). Accordingly, numbers of polyfunctional CD8+ T cells increased shortly after Treg depletion, but this effect was not sustained (Fig. 3C).Taken together, these results demonstrate early induction of TNF and IFNγ-producing CD8+ T cells during HBV infection that is controlled by Tregs. To investigate whether initial depletion of Tregs influences the establishment of HBV-specific CD8 T cells and ultimately the development of memory T cells, we quantified the

numbers of intrahepatic HBV-specific CD8+ T cells during the course of infection using Kb multimer staining (Fig. 4A) and characterized their differential selleck chemical expression of the survival factor CD127 and the homing receptor CD62L (Fig. 4B). Multimer staining revealed that HBc- and S-protein–specific CD8+ T cell populations expanded continuously in the liver, increasing from below 0.5% of all CD8+ LALs on day 7 to 2%-6% on day 70 (Fig. 4A). To our surprise, no differences were found when Treg-depleted and nondepleted mice were compared (Fig. 4A) clearly demonstrating Erlotinib that Tregs did not impair development of HBV-specific CD8+ T cells following AdHBV infection. Although on day 7 postinfection most

HBV-specific CD8+ T cells were of the effector or effector memory phenotype, a growing population of HBc93-100 (Fig. 4C, upper panel) and HBs190-197-specific (Fig. 4C, lower panel) CD8+ T cells with a central memory T cell phenotype (i.e., CD62LhighCD127+) emerged over time. In the late phase of infection (day 70), 70%-90% of HBV-specific CD8+ T cells in the liver were CD62LhighCD127+ central memory cells (Fig. 4C), indicating

that virus-specific central memory T cells reside not only in lymphoid tissues, but also in the liver. Although leading to a slightly reduced frequency of HBc93-100-specific CD8+ T cells on day 44, depletion of Tregs during the early phase of infection did not influence the establishment of long-term HBV-specific memory CD8+ T cells. The first line of defense against viral infections is the innate immune system, in which activation of macrophages and dendritic cells (DCs) plays a prominent role. Cytokines released by these cells contribute to inflammation and may Histidine ammonia-lyase suppress viral replication. To find out whether Tregs also exert regulatory effects on macrophages and DCs, we quantified F4/80+ macrophages and 33D1+MHCII+ DCs during the course of infection by flow cytometry and analyzed their IFNγ and TNFα secretion. We found a pronounced recruitment of macrophages into the liver until day 7 postinfection, which was enhanced at day 3 postinfection after depletion of Tregs (Fig. 5A). Upon Treg depletion, there was no change in the dynamics or relative numbers of macrophages producing IFNγ or TNFα spontaneously ex vivo.