探討小鼠自體免疫腦下垂體炎之病理機制：浸潤腦下垂體免疫細胞的增生

Abstract

摘要 自體免疫腦下垂體炎 (Autoimmune hypophysitis, AH) 是一個逐漸受到重視的腦下垂體疾病。這個疾病的典型症狀有頭痛、視覺障礙、內分泌功能缺損。其病理特徵是淋巴細胞 (T與B 細胞) 浸潤腦下垂體。然而目前對自體免疫腦下垂體炎的致病機制了解十分有限。在這個研究中，我們利用小鼠模式去探討浸潤腦下垂體的淋巴細胞是否在進行增殖，而如果答案是肯定的，又是何種細胞正在進行增殖。我們誘發小鼠產生自體免疫腦下垂體炎，以proliferating cell nuclear antigen (PCNA) 抗體，利用免疫組織化學染色，發現發病小鼠的腦下垂體中，有許多免疫細胞在進行增生。相較之下，在只有施打免疫完全佐劑的控制組小鼠中，只有少量的細胞在增生。我們利用雙重免疫組織化學染色，使用PCNA和淋巴細胞標誌物的抗體，發現浸潤腦下垂體的T細胞及B細胞在增生。另外有一些腦下垂體內分泌細胞也在增生，可能是腦下垂體遭受淋巴細胞浸潤破壞，因而產生的自我修復。我們使用流式細胞儀分析，也發現浸潤腦下垂體的T細胞中，有約4.53%的細胞在進行增生。而浸潤腦下垂體的B細胞中，有約2.2%的細胞在進行增生。進一步分析發現約4.6%的CD4+ T細胞在進行增生。而有約8.3%的CD8+ T細胞在進行增生。本研究證明了在小鼠的自體免疫腦下垂體炎，浸潤腦下垂體的免疫細胞會在腦下垂體進行增生，此結果使我們對自體免疫腦下垂體炎的致病機制有更進一步的認識，這個發現也可以解釋細胞毒性藥物 (cytotoxic drugs)，如azathioprine，可以藉由抑制細胞分裂來治療自體免疫腦下垂體炎的原因。

Abstract Autoimmune hypophysitis (AH) is an increasingly recognized disease of the pituitary gland. AH of typically presents with headache, visual-field defects and hormonal deficiencies. The defining pathological feature of AH is lymphocytic infiltration (T and B cells) in the pituitary, however, current understanding to the pathogenesis of AH is very limited. In this study, we aimed to explore whether pituitary-infiltrating lymphocytes proliferate, and if the answer is positive, what kind of cells proliferate, in a mouse model we have previously established. We induced experimental autoimmune hypophysitis (EAH) in the mouse model and studied the proliferation of the pituitary-infiltrating cells by immunohistochemistry. We found that considerable more cells proliferated in the pituitaries of mice that developed EAH, as demonstrated by immunohistochemical stainings using an antibody against proliferating cell nuclear antigen (PCNA). In contrast, only little proliferative activities were noted in the pituitaries of control mice immunized by adjuvants only. By double immunohistochemical staining against PCNA and lymphocyte markers, we found that a portion of pituitary-infiltrating T cells and B cells proliferated in this mouse model. Proliferating T and B cells scattered within the parenchyma of the pituitaries, suggesting a possible mechanism of sustained inflammation caused by T and B cells in the pituitary. Finally, some pituitary parenchymal cells also proliferated, suggesting a regeneration mechanism to compensate the lost pituitary cells caused by inflammation. We confirmed that 4.53% of pituitary-infiltrating T cells and 2.2% of pituitary-infiltrating B cells proliferated by flow cytometry analysis. 4.6% of pituitary-infiltrating CD4+T cell proliferated and 8.3% of pituitary-infiltrating CD8+ T cells proliferated, as demonstrated by flow cytometry analysis. Here we show that pituitary-infiltrating lymphocytes proliferate in situ in EAH. Our results provide a deeper understanding to the pathogenesis of autoimmune hypophysitis. Furthermore, these finding may explain how some cytotoxic drugs such as azathioprine may treat autoimmune hypophysitis.