胸腺细胞在胸腺外凋亡的形态学证据

In vitro thymus explants culture designed in this paper can mimic the thymic microenvironment 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 explants, 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 intrathymic 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.     

小鼠胸腺髓质上皮细胞系体内诱导胸腺细胞功能成熟

来源于BALB/c小鼠 (H-2^d)胸腺的髓质上皮细胞系MTEC1细胞表达H-2^d和I -A^d 分子 .为研究上皮细胞诱导胸腺细胞阳性选择及功能分化的能力 ,首先用γ 线照射C5 7BL/6J小鼠(H-2^d) ,再经静脉注射 (H-2^b×d)F1代骨髓细胞 ,制备 H-2^b×d→H-2^b)嵌合体 ,然后将MTEC1细胞注射到嵌合体胸腺内 .注射后 2个月 ,经HE染色显示 ,MTEC1细胞在嵌合体小鼠胸腺被膜下皮质区成簇存在 ,体外免疫学试验发现 ,嵌合体小鼠脾细胞含有抗原特异性H-2^d识别限制的杀伤T细胞 (CTL) ,IL -2产生T细胞及增殖应答T细胞 .在MLR试验中 ,嵌合体小鼠脾细胞显示对H-2^d 同种异型抗原的明显耐受 .从而证明MTEC1髓质上皮细胞能在胸腺微环境内诱导H-2^d识别限制的对特异抗原应答的T细胞发育及功能成熟 .由此提出在胸腺髓质区进行“2次胸腺选择”的假说 ,并讨论了其意义 .     

皮下组织的结构和功能

皮下组织即浅筋膜,由疏松结缔组织和脂肪组织构成.组成皮下的疏松结缔组织又叫蜂窝组织,其结构特点是纤维分布比较疏松,而基质相对较多(图1),由于有胶原纤维和弹性纤维交织在一起,既有韧性,又有弹性,故可使器官、组织的形态和位置既有相对的固定性,又具一定的可变性.其基质呈均质胶状,主要化学成分为粘蛋白和水等,粘蛋白是由透明质酸、硫酸软骨素A、c等与蛋白质结合而成,其中以透明质酸最为重要,透明质酸是个长分子(拉长达2.5×10~-6,分子之间有微小的间隙,形成分子筛.它可使小于其孔隙的物质,如水溶性的电解质、代谢产物、清蛋白等,很容易通过,如皮下注射     

胸腺细胞在胸腺外凋亡的形态学证据

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。     

Effect of mouse thymic medullary epithelial cell line on thymocyte development and functional maturation in vivo

Ｄｕｒｉｎｇｔｈｙｍｉｃｄｅｖｅｌｏｐｍｅｎｔ,ｉｎｔｅｒａｃｔｉｏｎｓｂｅｔｗｅｅｎＴＣＲｏｎｔｈｙｍｏｃｙｔｅｓａｎｄＭＨＣｍｏｌｅｃｕｌｅｓｏｎｔｈｙｍｉｃｓｔｒｏｍａｌｃｅｌｌｓｄｅｔｅｒｍｉｎｅｔｈｅｆａｔｅｏｆｉｍｍａｔｕｒｅｔｈｙｍｏｃｙｔｅｓ[1].(ｉ)Ｐｏｓｉｔｉｖｅｓｅｌｅｃｔｉｏｎ:ｔｈｅｍａｔｕｒａｔｉｏｎｏｆｔｈｙｍｏｃｙｔｅｓｉｎｔｏｓｅｌｆＭＨＣｒｅｓｔｒｉｃｔｅｄａｎｔｉｇｅｎｓｐｅｃｉｆｉｃａｎｄｓｅｌｆｔｏｌｅｒａｎｔＴｃｅｌｌｓ;(ｉｉ)ｎｅｇｅｔｉｖｅｓｅｌｅｃｔ…