Epithelial cell specificity and apotope recognition by serum autoantibodies in primary biliary cirrhosis

Abstract

A major enigma of primary biliary cirrhosis (PBC) is the selective targeting of biliary cells. Our laboratory has reported that following apoptosis human intrahepatic biliary epithelial cells (HiBEC) translocate the E2 subunit of the pyruvate dehydrogenase complex immunologically intact into apoptotic bodies, forming an apotope. However, the cell type and specificity of this reaction has not been fully defined. To address this issue we have investigated whether PDC-E2, BCOADC-E2, OGDC-E2, four additional inner mitochondrial enzymes and four nuclear antigens remain immunologically intact with respect to post-apoptotic translocation in HiBEC and 3 additional control epithelial cells. We report that all three 2-oxo acid dehydrogenase enzymes share the ability to remain intact within the apotope of HiBEC. Interestingly the E2 subunit of the branched chain 2-oxo acid dehydrogenase complex also remained intact in the other cell types tested. We extended the data using 95 AMA+ and 19 AMA- PBC and 76 control sera for reactivity against the 7 mitochondrial proteins studied herein and also the ability of AMA- sera to react with HIBEC apotopes. Sera from 3/95 AMA+ sera, but none of the controls, reacted with 2, 4-dienoyl CoA reductase 1 (DECR1), an enzyme also present intact only in the HiBEC apotope; DECR1 has not been previously associated with any autoimmune disease. Finally the specificity of HIBEC apotope reactivity was confined to AMA+ sera. In conclusion, we submit that the biliary specificity of PBC is secondary to the unique processes of biliary apoptosis.

Presence of disease specific autoantibodies against liver sinusoidal cells in primary biliary cirrhosis

“…Panels of mouse monoclonal antibodies and human combinatorial autoantibodies against specific antigens, such as members of the ODC family [4,6,[25][26][27] or the gp210 antigen [19,28] , have been used in paraffin-embedded liver sections, and their significance in diagnosis and prognosis has been verified. Tsuneyama et al [4] have demonstrated that both AMApositive and AMA-negative PBC patients, but not controls, have abnormal expression of either PDC-E2 or a cross-reacting molecule in the apical region of the biliary epithelium.…”

The modulation of co-stimulatory molecules by circulating exosomes in primary biliary cirrhosis

“…6 We have previously demonstrated that apoptotic bodies from biliary epithelial cells contained the PBC-specific mitochondrial autoantigens. 26 Hence, within the liver, it is likely that biliary epithelial cells may produce exosomes that are critical for the homeostasis of biliary function 52,53 and we further hypothesize that exosomes released by damaged bile duct cells may augment this process. Indeed, since circulating exosomes can be internalized efficiently by APC (as shown in Figure 2), it is likely that such cells are involved in the processing and presentation of autoantigen to autoreactive T cells.…”

“…[11][12][13][14][15] Data from human studies and animal models demonstrate that the pathogenesis of PBC involves not only autoreactive T cells and other immune cells [16][17][18][19][20][21][22] but also biliary epithelial cells. 12,18,19,[23][24][25][26][27][28][29][30] Herein, we demonstrate that circulating exosomes from PBC could be taken up by antigenpresenting cells (APCs) and affect the expression of cell surface co-stimulatory molecules. We also demonstrate that circulating exosomes in PBC contain altered patterns of miRNA expression with elevated miRNA-451a and miRNA-642-3p compared to healthy adults.…”

New Insights into Aging Process with a Focus on Cell Morphology, Autophagy and Role of Macrophages and NFAT

“…Apoptosis is induced with bile salts as described previously [21][22], with minor modifications. Briefly, PKH-26-labelled or unlabelledHiBECs were incubated in culture medium containing 1 mM sodium glycochenodeoxycholate (GCDC; Sigma-Aldrich) at 37°C for 4 h. The apoptosis rate was assessed by flow cytometry after staining with 7-aminoactinomycin D (7-AAD) and fluorescein isothiocyanate (FITC)-annexin V (BD Biosciences, San Jose, CA, USA).…”