HSC share many features with professional antigen-presenting cells (APCs),11 and have been shown to process and present antigen to T cells.12 T cell

activation requires Caspase inhibitor clinical trial interaction of the T cell receptor (TCR) with cognate peptide antigen presented in the context of major histocompatibility complex (MHC) on APC, as well as the interaction of ligand-receptor pairs providing costimulatory signals. Once T cells are activated, coinhibitory molecules play a role in dampening the T cell response, serving as an “off-switch.” APC regulate T cell responses through the balance of signals delivered through costimulatory and coinhibitory molecules, with B7 family ligands expressed on APC playing a major role in T cell mediated immunity.13 Accumulated evidence demonstrates that there are at least seven members present in the B7 family, namely, B7-1

(CD80), B7-2 (CD86), B7-H1 (PD-L1), B7-DC (PD-L2), B7-H2, B7-H3, and B7-H4.14 B7-1 and B7-2 interact with the receptor CD28 on T cells to provide costimulatory signals as well as interacting with CTLA4 to provide coinhibitory signals. B7-H1 LDK378 price and B7-DC interact with PD-1 to induce T cell apoptosis. B7-H2 interacts with ICOS on T cells and provides a costimulatory signal. B7-H3 and B7-H4 are newly identified ligands that inhibit T cell responses by interacting with as yet unidentified receptors.15 In the present study we investigated the impact of AHSC on adaptive

immune responses in the context of B7 family members using an in vitro mouse model. AHSC express the selleck coinhibitory molecule B7-H4, which provides a signal to dampen antigen-specific T cell responses. This work bears important implications for the dysfunctional immune responses that are often described in liver fibrosis, which is the natural environment of AHSC, and suggests a major role of these cells in modulating T cell immunity. α-SMA, alpha smooth muscle actin; AHSC, activated hepatic stellate cells; APCs, antigen presenting cells; CFSE, carboxyfluorescein diacetate succinimidyl ester; FACS, fluorescence activated cell sort; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GFAP, glial fibrillary acidic protein; HCV, hepatitis C virus; HSC, hepatic stellate cells; IFNγ, interferon gamma; IL-2, interleukin 2; LCMV, lymphocytic choreomeningitis virus; MAPK, mitogen activated protein kinase; MFI, mean fluorescence intensity; MHC, major histocompatibility complex; QHSC, quiescent hepatic stellate cells; TCR, T cell receptor. C57BL/6 mice (Jackson Laboratory) were used for HSC isolation. CD8+ T cells specific for lymphocytic choreomeningitis virus (LCMV) glycoprotein gp33-41 were isolated from spleens of P14 TCR transgenic mice. HSCs were isolated from mouse livers as described.