Abstract
The thymus is an intricate primary lymphoid organ, wherein bone marrow–derived lymphoid progenitor cells are induced to develop into functionally competent T cells that express a diverse TCR repertoire, which is selected to allow for the recognition of foreign Ags while avoiding self-reactivity or autoimmunity. Thymus stromal cells, which can include all non–T lineage cells, such as thymic epithelial cells, endothelial cells, mesenchymal/fibroblast cells, dendritic cells, and B cells, provide signals that are essential for thymocyte development as well as for the homeostasis of the thymic stroma itself. In this brief review, we focus on the key roles played by thymic stromal cells during early stages of T cell development, such as promoting the homing of thymic-seeding progenitors, inducing T lineage differentiation, and supporting thymocyte survival and proliferation. We also discuss recent advances on the transcriptional regulation that govern thymic epithelial cell function as well as the cellular and molecular changes that are associated with thymic involution and regeneration.
Footnotes
This work was supported by grants from the Natural Sciences and Engineering Research Council (2016-06592) and the Canadian Institutes of Health Research (154332). J.C.Z.-P. was supported by a Canada Research Chair in Developmental Immunology.
Abbreviations used in this article:
- CMJ
- corticomedullary junction
- cTEC
- cortical TEC
- DC
- dendritic cell
- DN
- double-negative
- DP
- double-positive
- E
- embryonic day
- ETP
- early thymic progenitor cell
- MHCII
- MHC class II
- mTEC
- medullary TEC
- SCF
- stem cell factor
- SP
- single-positive
- TEC
- thymic epithelial cell
- TSP
- thymic-seeding progenitor
- WT
- wild-type.
- Received July 28, 2020.
- Accepted October 29, 2020.
- Copyright © 2021 by The American Association of Immunologists, Inc.
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