Combination of experimental mouse models with single-cell RNA-sequencing creates a detailed map of medullary thymic epithelial cell development and identifies a transit-amplifying population as the immediate precursor to Aire-expressing mTECs.

Thymocyte-attracting CCL21-expressing embryonic mTECs carry a developmental potential to give rise to self-antigen-displaying Aire-expressing mTECs.

Self-reactive CD4⁺ thymocytes have a broad impact on the composition of medullary thymic epithelial cell (mTEC) subsets by acting upstream of Aire⁺ mTECs, which conditions the induction of T-cell tolerance.

The combination of single-cell analysis and cell fate mapping studies evidenced the presence of AIRE-expressing transit-amplifying thymic epithelial cells, which differentiate into mature medullary thymic epithelial cells expressing tissue-specific antigens.

The Aire-dependent genes show a preference for short 3’UTR transcript isoforms resulting in the escape from the post-transcriptional repression mediated by miRNAs in medullary thymic epithelial cells.

Thymus ageing is characterised by both compositional and transcriptional shifts amongst epithelial cells that perturb their differentiation, contribute to organ atrophy and ultimately impair immune function.

Thymic stromal cells help to develop and shape the gamma delta T cell pool.

Two-photon microscopy, combined with chemotaxis assays, synchronized thymocyte selection studies, and flow cytometry analyses, reveal that CCR4 and CCR7 promote medullary entry and central tolerance of immature and mature post-positive selection thymocyte subsets, respectively, with distinct outcomes for central tolerance.

Thymic macrophages are unique phagocytes with antigen-presenting abilities that comprise a Timd4⁺ subset of embryonic origin located in the cortex and a Cx3cr1⁺ subset derived from adult hematopoietic stem cells residing in the medulla.

Adoptive transfer and genetic manipulation revealed a previously unknown sub-population of PLZFhi CCR7+ iNKT cells as precursors for all three iNKT effector subsets in both thymus and periphery in mice.