The relationship between bile duct damage and portal fibrosis in chronic liver diseases remains unclear. This study was designed to show whether human intrahepatic biliary epithelial cells can undergo epithelial–mesenchymal cell transition, thereby directly contributing to fibrogenesis. Primary human cholangiocytes were stimulated with transforming growth factor-β (TGFβ) or TGFβ-presenting T cells and examined for evidence of transition to a mesenchymal phenotype. Liver sections were labelled to detect antigens associated with biliary epithelial cells (cytokeratin 7 and 19 and E-cadherin), T cells (CD8), epithelial–mesenchymal transition (S100A4, vimentin and matrix metalloproteinase-2 (MMP-2)), myofibroblasts (α-smooth muscle actin) and intracellular signal-transduction mediated by phosphorylated (p)Smad 2/3; in situ hybridisation was performed to detect mRNA encoding TGFβ and S100A4. Stimulation of cultured cells with TGFβ induced the expression of pSmad2/3, S100A4 and α-smooth muscle actin; these cells became highly motile. Although normal bile ducts expressed ALK5 (TGFβ RI), low levels of TGFβ mRNA and nuclear pSmad2/3, they did not express S100A4, vimentin or MMP-2. However, TGFβ mRNA and nuclear pSmad2/3 were strongly expressed in damaged ducts, which also expressed S100A4, vimentin and MMP-2. Fibroblast-like cells which expressed S100A4 were present around many damaged bile ducts. Cells in the ‘ductular reaction’ expressed both epithelial and mesenchymal markers together with high levels of TGFβ mRNA and pSmad2/3. In conclusion, the cells forming small- and medium-sized bile ducts and the ductular reaction undergo EMT during chronic liver diseases, resulting in the formation of invasive fibroblasts; this process may be driven by a response to local TGFβ, possibly presented by infiltrating T cells.

Background. Tubulitis is a defining feature of renal allograft rejection. Graft dysfunction may result from damage inflicted on tubular epithelial cells by intratubular cytotoxic T lymphocytes. Graft cells are known to produce chemokines during acute rejection, but it is not known whether changes in expression of specific chemokines can influence the composition of the intratubular lymphocyte population. We examined expression of individual chemokines in biopsy sections showing different pathological rejection grades. Methods. Sections from Banff-graded transplant biopsies were examined for the presence of β-chemokines (MCP-1, MIP-1α, MIP-1β, and RANTES) by immunofluorescence and semiquantitative confocal laser scanning microscopy. Results. β-Chemokines were expressed predominantly at the basolateral surface of tubular epithelial cells. Expression of MCP-1 and MIP-1β was significantly higher in sections showing grade 2 rather than grade 1 acute rejection. RANTES and MIP-1α showed no significant variation in level of expression between rejection grades. Conclusions. β-Chemokines are expressed by tubular epithelial cells during acute rejection. Consistent expression of RANTES and MIP-1α suggests a general role in recruiting T lymphocytes. However, MCP-1 and MIP-1β may play a more subtle role in recruitment of specific T-cell subsets, such as Th1 cells, during acute cellular rejection.

Professional antigen-presenting cells, such as dendritic cells, macrophages and B cells have been implicated in the pathogenesis of rheumatoid arthritis, constituting a possible target for antigen-specific immunotherapy. We addressed the possibility of blocking antigen presentation of the type II collagen (CII)-derived immunodominant arthritogenic epitope CII_259–273 to specific CD4 T cells by inhibition of antigen uptake in HLA-DR1-transgenic mice in vitro and in vivo. Electron microscopy, confocal microscopy, subcellular fractionation and antigen presentation assays were used to establish the mechanisms of uptake, intracellular localization and antigen presentation of CII by dendritic cells and macrophages. We show that CII accumulated in membrane fractions of intermediate density corresponding to late endosomes. Treatment of dendritic cells and macrophages with cytochalasin D or amiloride prevented the intracellular appearance of CII and blocked antigen presentation of CII_259–273 to HLA-DR1-restricted T cell hybridomas. The data suggest that CII was taken up by dendritic cells and macrophages predominantly via macropinocytosis. Administration of amiloride in vivo prevented activation of CII-specific polyclonal T cells in the draining popliteal lymph nodes. This study suggests that selective targeting of CII internalization in professional antigen-presenting cells prevents activation of autoimmune T cells, constituting a novel therapeutic strategy for the immunotherapy of rheumatoid arthritis.