Surh C D, Ernst B, Sprent J
Department of Immunology, Scripps Research Institute, La Jolla, California 92037.
J Exp Med. 1992 Aug 1;176(2):611-6. doi: 10.1084/jem.176.2.611.
Epithelial cells in the thymic medulla are conspicuous in normal adult mice, but sparse in the early fetal thymus and the thymus of adult T cell-deficient SCID mice. To examine whether growth of medullary epithelial cells (MEC) depends upon local contact with mature T cells, we used the finding that the SCID thymus is unusually permeable to mature T cells entering from the bloodstream. When SCID mice received multiple injections of mature lymph node T cells from birth, the thymus accumulated large numbers of mature TCR+ T cells of resting phenotype, but contained virtually no immature (CD4+8+) cells. The injected T cells localized in the medullary region of the thymus and led to marked regeneration of MEC. These and other data suggest that the growth of MEC is under the control of mature T cells. Placing MEC under T cell control might be a device for regulating the size and integrity of the medulla, especially during the phase of rapid thymic growth. Maintaining the cellular components of the medulla in proper balance could be critical for ensuring efficient self tolerance induction.
在正常成年小鼠中，胸腺髓质中的上皮细胞很明显，但在早期胎儿胸腺和成年T细胞缺陷的SCID小鼠的胸腺中则很稀疏。为了研究髓质上皮细胞（MEC）的生长是否依赖于与成熟T细胞的局部接触，我们利用了SCID胸腺对从血液中进入的成熟T细胞具有异常通透性这一发现。当SCID小鼠从出生起多次注射成熟淋巴结T细胞时，胸腺积累了大量具有静止表型的成熟TCR+ T细胞，但几乎不包含未成熟（CD4+8+）细胞。注入的T细胞定位于胸腺的髓质区域，并导致MEC显著再生。这些以及其他数据表明，MEC的生长受成熟T细胞的控制。将MEC置于T细胞控制之下可能是一种调节髓质大小和完整性的机制，尤其是在胸腺快速生长阶段。维持髓质细胞成分的适当平衡对于确保有效的自身耐受诱导可能至关重要。
