胸腺在适应性免疫系统中发挥各种不同功能，包括通过胸腺上皮细胞产生自体可以容忍的胸腺细胞，它们发育成T-淋巴细胞。人们曾广泛假设胸腺只含有前体上皮细胞，细胞类型也是有限的。
但对培养中的大鼠胸腺上皮细胞所做研究表明，如果暴露于皮肤微环境，它们可以被重新编程而具有毛囊多能干细胞的命运。这些细胞可以被克隆和有选择性地培养，这些都是与人胸腺上皮细胞的可能生长以及潜在临床应用相关的特性。
生物谷推荐原始出处：
Nature doi:10.1038/nature09269
Microenvironmental reprogramming of thymic epithelial cells to skin multipotent stem cells
Paola Bonfanti,Stéphanie Claudinot,Alessandro W. Amici,Alison Farley,C. Clare Blackburn" Yann Barrandon
The thymus develops from the third pharyngeal pouch of the anterior gut and provides the necessary environment for thymopoiesis (the process by which thymocytes differentiate into mature T lymphocytes) and the establishment and maintenance of self-tolerance1, 2, 3. It contains thymic epithelial cells (TECs) that form a complex three-dimensional network organized in cortical and medullary compartments, the organization of which is notably different from simple or stratified epithelia4. TECs have an essential role in the generation of self-tolerant thymocytes through expression of the autoimmune regulator Aire5, 6, but the mechanisms involved in the specification and maintenance of TECs remain unclear7, 8, 9. Despite the different embryological origins of thymus and skin (endodermal and ectodermal, respectively), some cells of the thymic medulla express stratified-epithelium markers10, 11, 12, interpreted as promiscuous gene expression. Here we show that the thymus of the rat contains a population of clonogenic TECs that can be extensively cultured while conserving the capacity to integrate in a thymic epithelial network and to express major histocompatibility complex class II (MHC II) molecules and Aire. These cells can irreversibly adopt the fate of hair follicle multipotent stem cells when exposed to an inductive skin microenvironment; this change in fate is correlated with robust changes in gene expression. Hence, microenvironmental cues are sufficient here to re-direct epithelial cell fate, allowing crossing of primitive germ layer boundaries and an increase in potency13.
