Cisternas P A, Armati P J
School of Biological Sciences, Building AO8, The University of Sydney, Sydney, NSW 2006, Australia,
Anat Embryol (Berl). 1999 Oct;200(4):433-43. doi: 10.1007/s004290050293.
We report for the first time the development and morphological characteristics of the spleen thymus, lymph nodes and liver of the northern brown bandicoot, Isoodon macrourus. To date few marsupial species have been studied. The development and morphological characteristics of the organs shared the typical features of those few other marsupials studied as well as those of eutherians. These suggest comparative functional properties with the eutherian immune system. The thymus differentiated within the first week of pouch life and showed evidence of immunolymphopoiesis up to juvenile stages. The spleen, though seeded by lymphocytes within the first week of pouch life, was slower to mature, but differentiated and showed signs of immunocompetency by the time young left the pouch. The mature spleen displayed the same anatomical blood filtering and immunosurveillance properties as that of the eutherian spleen, with evidence of erythrocyte destruction, thrombopoietic activity, activation and differentiation of immunocompetent lymphocytes. However, the absence of sheathed capillary structures in the spleen may indicate differences in the humoral response to circulating antigens. Similarly, lymph nodes also mature by this stage with anterior nodes appearing before posterior nodes. The mature lymph nodes displayed structural features of secondary immuno-lymphoid organs consistent with production of immune responses. Finally, the liver displayed haemopoietic activity for the first four weeks of pouch life. The pattern of development in the bandicoot appears to parallel the pattern reported for other marsupials, yet the thymus matures considerably earlier than previously reported and may be of significance in the development and onset of cell-mediated immunity. Current studies to characterise cellular components, such as T/B lymphocyes and accessory cells of these organs will help to define the mechanisms of immune recognition, activation and hence outline the basis of the marsupial humoral and cellular immunity.
我们首次报告了北褐袋鼹（Isoodon macrourus）脾脏、胸腺、淋巴结和肝脏的发育情况及形态特征。迄今为止，对有袋类物种的研究较少。这些器官的发育和形态特征既具有已研究的其他少数有袋类动物的典型特征，也具有真兽类动物的典型特征。这表明它们与真兽类免疫系统具有比较性功能特性。胸腺在育儿袋生活的第一周内分化，并在幼年期之前都显示出免疫淋巴细胞生成的迹象。脾脏虽然在育儿袋生活的第一周内就有淋巴细胞定植，但成熟较慢，但在幼崽离开育儿袋时已分化并显示出免疫活性迹象。成熟的脾脏具有与真兽类脾脏相同的解剖学血液过滤和免疫监视特性，有红细胞破坏、血小板生成活性以及免疫活性淋巴细胞激活和分化的证据。然而，脾脏中缺乏被膜毛细血管结构可能表明对循环抗原的体液反应存在差异。同样，淋巴结在这个阶段也成熟，前淋巴结比后淋巴结先出现。成熟的淋巴结显示出二级免疫淋巴器官的结构特征，与免疫反应的产生一致。最后，肝脏在育儿袋生活的前四周具有造血活性。袋鼹的发育模式似乎与其他有袋类动物报告的模式相似，但胸腺成熟的时间比以前报告的要早得多，这可能在细胞介导免疫的发育和起始中具有重要意义。目前对这些器官的细胞成分（如T/B淋巴细胞和辅助细胞）进行表征的研究将有助于确定免疫识别、激活的机制，从而概述有袋类动物体液免疫和细胞免疫的基础。
