The adaptive phenotype of cortical thymic epithelial cells.
Epithelial cells in the thymus are required for positive and negative selection of developing thymocytes. Although medullary epithelial cells play a major role in negative selection owing to their facility of expressing peripheral self-antigens, the adaptive features of cortical epithelial cells are largely unknown. A paper in this issue of the European Journal of Immunology shows that the putative serine protease Prss16 affects positive selection of a subset of CD4(+) T cells. A survey of chordate genomes indicates that the Prss16 gene emerged in vertebrates as a paralogue of evolutionarily older members of the serine carboxypeptidase 28 family; thus, Prss16 is not associated with the appearance of the adaptive immune system and the thymus in jawed vertebrates. Nevertheless, it appears that Prss16 has later evolved as an essential contributor to the MHC class II peptide/ligand repertoire.
Department of Developmental Immunology, Max-Planck-Institute of Immunobiology, Stuebeweg, Freiburg, Germany. boehm@immunbio.mpg.de
Thomas
T
Boehm
D000818:Animals; D005075:Biological Evolution; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D004847:Epithelial Cells / Q000276:immunology* / Q000378:metabolism; D006649:Histocompatibility Antigens / Q000276:immunology / Q000378:metabolism; D051379:Mice; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000276:immunology*; D012697:Serine Endopeptidases / Q000235:genetics / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology* / Q000378:metabolism
D006649:Histocompatibility Antigens; C472501:Prss16 protein, mouse; D012697:Serine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C520309:proteasome subunit beta5t, mouse