11 In general, HSCs actively shape local hepatic immune regulation through the release of soluble mediators with immune function and through the promotion of lymphocyte chemotaxis and adherence.12 HSCs have potent innate immune functions13 and, by executing these innate immune functions, promote hepatic fibrogenesis.14 HSCs can contribute to the local induction of T cell immunity by antigen presentation to CD4 and CD8 T cells.15 However, these cells have also been reported to eliminate alloantigen-specific

T cells during mixed lymphocyte reactions,16 to suppress DCs through interleukin-10 (IL-10),17 and to protect hepatic islet allografts from T cell–mediated rejection.18 Furthermore, they can expand regulatory T cells (Tregs) see more in an IL-2–dependent manner.19 Here we examine whether HSCs Akt inhibitor control the development of

T cell immunity in a non–MHC-restricted fashion. We provide evidence that HSCs directly interact with T cells in a CD54-dependent fashion as a third-party inhibitory cell population. α-SMA, α-smooth muscle actin; Ad, adenovirus; APC, antigen-presenting cell; CCL4, carbon tetrachloride; CFSE, carboxyfluorescein succinimidyl ester; d, day; DC, dendritic cell; DI, division index; ELISA, enzyme-linked immunosorbent assay; GFAP, glial fibrillary acidic protein; HSC, hepatic stellate cell; HSC-CM, hepatic stellate cell–conditioned medium; IFN-γ, interferon-γ; Ig, immunoglobulin; IL, interleukin; LFA-1, lymphocyte function-associated antigen 1; LPS, lipopolysaccharide; LSEC, liver sinusoidal endothelial cell; MHC, major histocompatibility complex; MOI, multiplicity of infection; OVA, ovalbumin; NS, not significant; PCR, polymerase chain reaction; pGFP, green fluorescent protein plasmid; PMA, phorbol 12-myristate 13-acetate; TCR, T cell receptor; TGF-β, transforming growth factor β; Treg, regulatory T cell. All animal experiments were performed in accordance with German legislation governing animal studies and the Principles of Laboratory Animal Care guidelines

(National Institutes check details of Health publication 85-23, 1996 revision). C57BL/6J, CD54−/−, BALB/c, and B6.C-H-2bm1 mice (bearing a point mutation in H-2Kb preventing the presentation of SIINFEKL), H-2KbSIINFEKL–restricted T cell receptor (TCR)–transgenic animals (OT-1), and H-2Kb–restricted Des-TCR mice were bred and maintained under specific pathogen-free conditions according to the guidelines of the Federation of Laboratory Animal Science Associations. Liver fibrosis was induced by intraperitoneal injections of carbon tetrachloride (CCL4; 0.5 μL/g of body weight) dissolved in an equal volume of sterile mineral oil twice per week for 6 weeks. Antibodies and reagents for flow cytometry were purchased from BD Bioscience (Heidelberg, Germany) or eBioscience (San Diego, CA). Quantitative enzyme-linked immunosorbent assays (ELISAs) were acquired from BD Biosciences.