Li Yan, Chen Pei, Huang Hao, Feng Huiyu, Ran Hao, Liu Weibin
Department of Neurosurgical Intensive Care Unit, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China.
Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, China.
Immun Ageing. 2021 Nov 18;18(1):44. doi: 10.1186/s12979-021-00255-8.
Dendritic cells (DCs) in the thymus are involved in central tolerance formation, but they also have other functions in the thymus, such as pathogen recognition. The density changes of human thymic DCs have been hardly investigated. In this study, human thymus samples of various ages were collected for tissue sectioning and staining. The thymic cortex and medulla area as well as the densities of various subsets of thymic DCs were calculated.
All common DC subsets were found in the human thymus of various ages. Most DCs had accumulated in the human thymic epithelial space, especially the medulla. We also found that the human thymic cortex had atrophied relatively faster than the medulla, which led to a gradual increase of the area ratio of the medulla to cortex with the increase of age. The densities of DC subsets in the human thymus showed various changes with increasing age, which contributed to the composition changes of DC subsets. The density of plasmacytoid DCs (pDCs) in the human thymus had increased gradually with aging, which suggested that pDCs plays another essential role in the thymus in addition to central tolerance.
Inconsistent with the shrinking of the epithelial space in the thymus, the densities of DC subsets in the epithelial space of the thymus are maintained at a constant level with aging to preserve highly efficient autoreactive thymocyte screening. An increasing density of the thymic pDCs with aging implies an extra function of DCs in the thymus beyond central tolerance.
胸腺中的树突状细胞（DCs）参与中枢耐受的形成，但它们在胸腺中也有其他功能，如病原体识别。人类胸腺DCs的密度变化几乎未被研究。在本研究中，收集了不同年龄的人类胸腺样本进行组织切片和染色。计算了胸腺皮质和髓质区域以及胸腺DCs各亚群的密度。
在不同年龄的人类胸腺中均发现了所有常见的DC亚群。大多数DCs聚集在人类胸腺上皮空间，尤其是髓质。我们还发现，人类胸腺皮质萎缩相对比髓质更快，这导致髓质与皮质的面积比随着年龄的增长而逐渐增加。人类胸腺中DC亚群的密度随着年龄的增长呈现出各种变化，这导致了DC亚群组成的变化。人类胸腺中浆细胞样DCs（pDCs）的密度随着衰老逐渐增加，这表明pDCs除了中枢耐受外，在胸腺中还发挥着另一个重要作用。
与胸腺上皮空间的缩小不一致，胸腺上皮空间中DC亚群的密度随着衰老保持在恒定水平，以维持高效的自身反应性胸腺细胞筛选。胸腺pDCs密度随着衰老增加意味着DCs在胸腺中除中枢耐受外还有额外功能。
