Taplin M E, Frantz M E, Canning C, Ritz J, Blumberg R S, Balk S P
Division of Hematology-Oncology, Beth Israel Hospital, Boston, MA 02215, USA.
Immunology. 1996 Mar;87(3):402-7. doi: 10.1046/j.1365-2567.1996.496571.x.
Several lines of evidence indicate that a subset of murine intestinal intraepithelial lymphocytes (iIEL), particularly those which express the CD8 alpha alpha homodimer, mature extrathymically. This study confirms that a small fraction of adult human iIEL also express the CD8 alpha alpha homodimer and demonstrates that most of these cells in the small intestine are T cells using the alpha beta T-cell receptor (TCR). Whether these cells or other subsets of adult human iIEL mature extrathymically in the intestine was assessed by measuring the expression of terminal deoxynucleotidyltransferase (TdT), an enzyme expressed exclusively by immature lymphocytes. Very low levels of TdT message could be detected by polymerase chain reaction (PCR) amplification in some iIEL samples. The level of TdT expression was assayed by competitive PCR amplification and compared with thymocytes and peripheral blood lymphocytes. These measurements indicated that the number of immature T cells expressing TdT in the intestinal epithelium was less than one cell per 10(7) lymphocytes. This demonstrates that there are few if any TdT expressing immature T cells in the adult human intestinal mucosa and indicates, therefore, that T-cell development in the intestinal mucosa does not contribute significantly to the T-cell repertoire of the adult human intestine.
多条证据表明，小鼠肠道上皮内淋巴细胞（iIEL）的一个亚群，特别是那些表达CD8αα同型二聚体的细胞，在胸腺外成熟。本研究证实，一小部分成年人类iIEL也表达CD8αα同型二聚体，并表明小肠中的大多数这些细胞是使用αβT细胞受体（TCR）的T细胞。通过测量末端脱氧核苷酸转移酶（TdT）的表达来评估这些细胞或成年人类iIEL的其他亚群是否在肠道中胸腺外成熟，TdT是一种仅由未成熟淋巴细胞表达的酶。在一些iIEL样本中，通过聚合酶链反应（PCR）扩增可检测到极低水平的TdT信息。通过竞争性PCR扩增测定TdT表达水平，并与胸腺细胞和外周血淋巴细胞进行比较。这些测量表明，肠道上皮中表达TdT的未成熟T细胞数量少于每10^7个淋巴细胞一个细胞。这表明在成年人类肠道黏膜中几乎没有表达TdT的未成熟T细胞，因此表明肠道黏膜中的T细胞发育对成年人类肠道的T细胞库贡献不大。
