Pharmazentrum Frankfurt/ZAFES, Klinikum der Johann Wolfgang Goethe Universität, Theodor-Stern Kai 7, 60590 Frankfurt am Main, Germany.
J Autoimmun. 2013 May;42:39-49. doi: 10.1016/j.jaut.2012.11.001. Epub 2012 Nov 28.
In our novel mouse model for autoimmune hepatitis (AIH), wildtype FVB mice infected with an Adenovirus (Ad) expressing the major AIH autoantigen human cytochrome P450 2D6 (hCYP2D6) show persistent histological and immunological features associated with AIH, including the generation of anti-hCYP2D6 antibodies with an epitope specificity identical to LKM-1 autoantibodies in AIH-patients. Since FVB mice do not express hCYP2D6, the immune response was directed against mouse CYP (mCYP) homologues. Additional expression of hCYP2D6 in transgenic mice resulted in amelioration of the liver disease. In the present study we used the CYP2D6 model to assess why tolerance breakdown and induction of autoimmune liver disease is more efficient if the triggering antigen is similar but not identical to the target autoantigen. We found that in contrast to the specificity and magnitude of anti-hCYP2D6 antibody responses, T-cell responses differ profoundly between wildtype and transgenic mice. Detailed T-cell epitope mapping studies show a robust, antigen-specific T-cell reactivity in FVB mice largely directed against one CD4 and three CD8 epitopes, activating a total of approximately 1% CD4 and 10% CD8 T-cells, respectively, while infected hCYP2D6 mice generated almost no hCYP2D6-specific T-cells. The frequency of hCYP2D6-specific T-cells was approximately 3-fold higher in the liver compared with the spleen. Amino acid sequence comparison revealed that the immunodominant epitopes were located in hCYP2D6-segments of intermediate homology between hCYP2D6 and its mCYP homologues. Our data indicate that self/non-self molecular mimicry, rather than molecular identity, is a prerequisite for breaking T-cell tolerance in the liver.
在我们用于自身免疫性肝炎（AIH）的新型小鼠模型中，感染表达主要 AIH 自身抗原人细胞色素 P450 2D6（hCYP2D6）的腺病毒（Ad）的野生型 FVB 小鼠显示出与 AIH 相关的持续性组织学和免疫学特征，包括生成与 AIH 患者中 LKM-1 自身抗体具有相同表位特异性的抗 hCYP2D6 抗体。由于 FVB 小鼠不表达 hCYP2D6，因此免疫反应针对的是鼠 CYP（mCYP）同源物。在转基因小鼠中额外表达 hCYP2D6 可改善肝脏疾病。在本研究中，我们使用 CYP2D6 模型来评估为什么如果触发抗原与靶自身抗原相似但不相同，则自身免疫性肝病的免疫耐受破坏和诱导更为有效。我们发现，与抗 hCYP2D6 抗体反应的特异性和幅度相比，T 细胞反应在野生型和转基因小鼠之间存在明显差异。详细的 T 细胞表位映射研究表明，FVB 小鼠中存在针对一个 CD4 和三个 CD8 表位的强大、抗原特异性 T 细胞反应，分别激活了约 1%的 CD4 和 10%的 CD8 T 细胞，而感染 hCYP2D6 的小鼠几乎没有产生针对 hCYP2D6 的特异性 T 细胞。与脾脏相比，肝脏中 hCYP2D6 特异性 T 细胞的频率大约高 3 倍。氨基酸序列比较表明，免疫优势表位位于 hCYP2D6 与 mCYP 同源物之间具有中等同源性的 hCYP2D6 片段中。我们的数据表明，自身/非自身分子模拟而不是分子同一性是在肝脏中打破 T 细胞耐受的前提。
