胸腺细胞在胸腺外凋亡的形态学证据

MORPHOLOGICAL EVIDENCE FOR THYMOCYTES APOPTOSIS OUTSIDE THE THYMUS

本文采用的胸腺外植块培养法实验既能够模拟胸腺微环境中胸腺细胞的发育周期又能够切断血液流通,理论上造成一种胸腺封闭状态(产生的胸腺细胞不能迁出胸腺外,假如某些胸腺细胞有迁出倾向,它也只能堆积于胸腺血管内)。培养3天后,在透射电子显微镜下观察到胸腺外植块血管内存在有胸腺细胞,并且处于不同的凋亡时期。本文的实验结果,在形态学上首次为胸腺外死亡假说找到了直接证据,说明胸腺细胞不必一定在胸腺原位死亡,它也可以获得死亡信号之后进入血管,随血液循环至外用最终死亡。但是这决不是意味着否定胸腺内死亡假说,因为我们同时观察到在胸腺基质细胞表面原位凋亡的胸腺细胞数量远超过进入血管后凋亡的胸腺细胞(但是在基质细胞表面凋亡的胸腺细胞并没有被基质细胞有效吞噬),所以我们的观点是:胸腺细胞同时存在胸腺内死亡和胸腺外死亡两种方式,一部分胸腺细胞在胸腺原位死亡的,而另一部分胸腺细胞是迁出胸腺后死亡溶解的。

In vitro thymus explants culture designed in this paper can mimic the thymic microenvi-ronment as it were in vivo. Theoretically,thymus explants are cut off free from blood stream. So if some developing or developed thymocytes had the inclination to migrate into the periphery, they would only be accumulated in the blood vessels within thymus explants. After 3- day's culture, under transmission electron microscope we observed the migrating thymocytes accumulated in the blood vessels of C57BL/6 mice thymus ex-plants, and these thymocytes were occurring apoptosis at different stage. To our knowledge, this findings offers the first morphological evidence that thymocytes do not necessarily die inside the thymus in situ,and that having acquired the death signals thymocytes can migrate into the blood stream and die quickly outside the thymus. But this is not to say that we deny the in-trathymic death hypothesis. On the contrary, we found the number of thymocytes occurring in situ apoptosis on the surfaces of stromal cells is far more than that of migrating into the blood vessels. So,our proposal is that there are two sites for thymocytes apoptosis, some die inside the thymus and the others die outside the thymus.