Laboratory of Immune Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
CCR Collaborative Bioinformatics Resource, Center for Cancer Research, Bethesda, MD 20892, USA.
Sci Immunol. 2023 Aug 25;8(86):eabo7975. doi: 10.1126/sciimmunol.abo7975. Epub 2023 Aug 18.
Thymic epithelial cells (TECs) produce glucocorticoids, which antagonize negative selection of autoreactive thymocytes and promote a competent T cell antigen-specific repertoire. To characterize their source, we generated a knock-in reporter mouse in which endogenous Cyp11b1, the final enzyme in de novo production of active glucocorticoids, was fluorescently tagged with mScarlet. Here, we find that Cyp11b1 is expressed in medullary TECs (mTECs) but not cortical TECs or other cells in the thymus. A distinct characteristic of mTECs is the presence of Aire, a transcription factor that drives expression of tissue-restricted antigens (TRAs) important for establishing immune tolerance. Cyp11b1 expression was highest in Aire mTECs, lower in post-Aire mTECs, and absent in mTECs of -deficient mice. Transcriptomic analyses found that multiple enzymatic biosynthetic pathways are expressed specifically in mTECs and are also Aire dependent. In particular, we found that the thymus expresses messenger RNA for enzymes that catalyze production of many bioactive steroids and that glucocorticoids and sex steroids were secreted by cultured thymi. Expression of the transcripts for these genes and production of their final steroid products were markedly reduced in the absence of Aire. Thus, in addition to its well-established role in inducing TRAs that promote negative selection, Aire has an additional and contrary function of inducing glucocorticoids that antagonize negative selection, which together may expand and enhance the TCR repertoire. Furthermore, because Aire drives expression of multiple enzymes responsible for production of other non-gene-encoded bioactive molecules, it might have yet other roles in thymus development and function.
胸腺上皮细胞 (TECs) 产生糖皮质激素，拮抗自身反应性胸腺细胞的阴性选择，并促进有能力的 T 细胞抗原特异性库。为了表征它们的来源，我们生成了一个敲入报告小鼠，其中内源性 Cyp11b1（从头产生活性糖皮质激素的最后一种酶）被 mScarlet 荧光标记。在这里，我们发现 Cyp11b1 在髓质 TECs（mTECs）中表达，但不在皮质 TECs 或胸腺中的其他细胞中表达。mTECs 的一个独特特征是存在 Aire，一种驱动组织限制性抗原 (TRA) 表达的转录因子，TRA 对建立免疫耐受很重要。Cyp11b1 的表达在 Aire mTECs 中最高，在 Aire 后 mTECs 中较低，在 -缺陷小鼠的 mTECs 中不存在。转录组分析发现，多个酶生物合成途径特异性表达在 mTECs 中，并且也依赖于 Aire。特别是，我们发现胸腺表达了催化多种生物活性类固醇产生的酶的信使 RNA，并且培养的胸腺分泌糖皮质激素和性激素。在没有 Aire 的情况下，这些基因的转录物表达和它们的最终类固醇产物的产生明显减少。因此，除了其在诱导促进阴性选择的 TRA 方面的既定作用外，Aire 还具有诱导拮抗阴性选择的糖皮质激素的额外和相反的作用，这两者可能会扩大和增强 TCR 库。此外，由于 Aire 驱动负责产生其他非基因编码生物活性分子的多种酶的表达，它在胸腺发育和功能中可能具有其他作用。
