Small M, Kaiser M, Tse W, Heimfeld S, Blumberg S
Department of Cell Biology and Histology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel.
Eur J Immunol. 1996 Apr;26(4):961-4. doi: 10.1002/eji.1830260438.
The activity of two peptidases was determined in immortalized lines of thymic stromal cells. A line of total stromal cells (T-TG-St) was grown from transgenic mouse expressing temperature-sensitive SV40 T antigen under the control of the regulatory elements of the mouse major histocompatibility complex class I gene. From these cells we isolated a subset (DP-TG-St) that binds thymocytes which are mainly CD4+8+. We also assayed a clone of fetal thymic epithelial cells (BA/10) that binds CD4+8+ thymocytes. Both lines of double -positive cell-binding stroma exhibited strong activity of two peptidases, neutral endopeptidase (NEP; EC 3.4.24.11) and aminopeptidase N (APN; EC 3.4.11.2). In contrast, the activity of both enzymes was very low in the total thymic stromal line. Use of the specific inhibitors confirmed that these two enzymes were responsible for the activity observed but also suggested the presence of additional unidentified aminopeptidase(s) in the same stromal cells. The high activity of the two peptidases on stromal cells that bind thymocytes at the double-positive stage raises the possibility that they might contribute to the microenvironment of the developing thymocytes.
在永生化胸腺基质细胞系中测定了两种肽酶的活性。总基质细胞系（T-TG-St）是从在小鼠主要组织相容性复合体I类基因调控元件控制下表达温度敏感型SV40 T抗原的转基因小鼠中培养而来。从这些细胞中，我们分离出了一个亚群（DP-TG-St），它能结合主要为CD4+8+的胸腺细胞。我们还检测了一个能结合CD4+8+胸腺细胞的胎儿胸腺上皮细胞克隆（BA/10）。这两个双阳性细胞结合基质系均表现出两种肽酶，即中性内肽酶（NEP；EC 3.4.24.11）和氨肽酶N（APN；EC 3.4.11.2）的强活性。相比之下，这两种酶在总胸腺基质系中的活性非常低。使用特异性抑制剂证实这两种酶是所观察到的活性的原因，但也表明在同一基质细胞中存在其他未鉴定的氨肽酶。这两种肽酶在双阳性阶段结合胸腺细胞的基质细胞上的高活性增加了它们可能对发育中的胸腺细胞微环境有贡献的可能性。
