Andjelić S, Jain N, Nikolić-Zugić J
Immunology Program, Memorial Sloan-Kettering Cancer Center, New York 10021.
Eur J Immunol. 1993 Sep;23(9):2109-15. doi: 10.1002/eji.1830230910.
CD8lo4lo cells are the immediate precursors of immature CD8hi4loTcRlo, CD8lo4hiTcRlo and CD8hi4hiTcRlo double-positive (DP) thymocytes in the adult murine thymus. These cells are the first subset in the adult thymus to express accessory CD8 and CD4 molecules, to rearrange the T cell receptor (TcR) alpha chain genes and to express the TcR alpha beta heterodimer at low levels at the surface. Here, we investigate the fetal ontogeny of CD8lo4lo cells. We detect these cells on day 15 of fetal development. They dominate the thymus on day 15.5, to become progressively less prominent thereafter. An important characteristic of fetal CD8lo4lo cells is the early expression of TcR alpha mRNA (on fetal day 15, 36-48 h earlier than reported previously). Our results also suggest, but do not prove, that the receptor may be expressed on the surface as early as day 15.5. Fetal CD8lo4lo cells, like their adult counterparts, become DP in vitro. However, early fetal CD8lo4lo thymocytes express both CD44 and CD25--unlike the adult subset--and that links them to their putative precursors, fetal CD44+CD25+ double-negative cells. This finding underscores the difference between adult and fetal thymocytes in turnover of membrane molecules and/or the kinetics of progression through phenotypic stages.
CD8lo4lo细胞是成年小鼠胸腺中未成熟的CD8hi4loTcRlo、CD8lo4hiTcRlo和CD8hi4hiTcRlo双阳性（DP）胸腺细胞的直接前体细胞。这些细胞是成年胸腺中首个表达辅助性CD8和CD4分子、重排T细胞受体（TcR）α链基因并在表面低水平表达TcRαβ异二聚体的细胞亚群。在此，我们研究了CD8lo4lo细胞在胎儿期的个体发生。我们在胎儿发育第15天检测到这些细胞。它们在第15.5天在胸腺中占主导地位，此后逐渐变得不那么突出。胎儿CD8lo4lo细胞的一个重要特征是TcRα mRNA的早期表达（在胎儿第15天，比先前报道的时间早36 - 48小时）。我们的结果还表明（但未证实），该受体最早可能在第15.5天在表面表达。胎儿CD8lo4lo细胞与其成年对应细胞一样，在体外会变成双阳性。然而，早期胎儿CD8lo4lo胸腺细胞表达CD44和CD25，这与成年细胞亚群不同，这将它们与其假定的前体细胞——胎儿CD44 + CD25 +双阴性细胞联系起来。这一发现强调了成年和胎儿胸腺细胞在膜分子更新和/或通过表型阶段进展的动力学方面的差异。
