Thymus-specific serine protease, a protease that shapes the CD4 T cell repertoire
Résumé
The lifespan of T cells is determined by continuous interactions of their T cell receptors (TCR) with self-peptide-MHC (self-
pMHC) complexes presented by different subsets of antigen-presenting cells (APC). In the thymus, developing thymocytes are
positively selected through recognition of self-pMHC presented by cortical thymic epithelial cells (cTEC). They are subsequently
negatively selected by medullary thymic epithelial cells (mTEC) or thymic dendritic cells (DC) presenting self-pMHC com-
plexes. In the periphery, the homeostasis of mature T cells is likewise controlled by the interaction of their TCR with self-pMHC
complexes presented by lymph node stromal cells while they may be tolerized by DC presenting tissue-derived self-antigens. To
perform these tasks, the different subsets of APC are equipped with distinct combination of antigen processing enzymes and
consequently present specific repertoire of self-peptides. Here, we discuss one such antigen processing enzyme, the thymus-
specific serine protease (TSSP), which is predominantly expressed by thymic stromal cells. In thymic DC and TEC, TSSP edits
the repertoire of peptide presented by class II molecules and thus shapes the CD4 T cell repertoire.