Differential priming of CD8 and CD4 T-cells in animal models of autoimmune hepatitis and cholangitis

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Abstract
The pathogenesis of autoimmune liver diseases is poorly understood. Animal models are necessary to investigate antigen presentation and priming of T-cells in the context of autoimmunity in the liver. Transgenic mouse models were generated in which the model antigen ovalbumin is expressed in hepatocytes (TF-OVA) or cholangiocytes (ASBT-OVA). Transgenic OT-I (CD8) or OT-II (CD4) T-cells specific for ovalbumin were adoptively transferred into TF-OVA and ASBT-OVA mice to induce in vivo priming of antigen-specific T-cells. T-cell migration and activation, as well as induction of liver inflammation, were studied. OT-I T-cells preferentially located to the liver of both mouse strains whereas no migration of OT-II T-cells to the liver was observed. OT-I T-cells proliferated in the liver of TF-OVA mice and the liver and liver draining lymph nodes of ASBT-OVA mice. OT-II CD4 T-cells were activated in spleen and liver draining lymph node of TF-OVA mice but not in ASBT-OVA mice. Transfer of OT-I T-cells led to histologically distinct inflammatory conditions in the liver of ASBT-OVA and TF-OVA mice and caused liver injury as determined by the elevation of serum alanine aminotransferase. Conclusion: An antigen expressed in hepatocytes is presented to CD8 and CD4 T-cells, whereas the same antigen expressed in cholangiocytes is presented to CD8 but not CD4 T-cells. In both models, activation of CD8 T-cells occurs within the liver and causes liver inflammation. The models presented here are valuable to investigate the priming of T-cells in the liver and their role in the development of autoimmune disease of the liver. (HEPATOLOGY 2007.)