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Thymic selection revisited: how essential is it?
Author(s) -
Von Boehmer Harald,
Aifantis Iannis,
Gounari Fotini,
Azogui Orly,
Haughn Loralee,
Apostolou Irina,
Jaeckel Elmar,
Grassi Fabio,
Klein Ludger
Publication year - 2003
Publication title -
immunological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.839
H-Index - 223
eISSN - 1600-065X
pISSN - 0105-2896
DOI - 10.1034/j.1600-065x.2003.00010.x
Subject(s) - biology , lineage (genetic) , t cell receptor , negative selection , cd8 , t cell , microbiology and biotechnology , il 2 receptor , clonal deletion , receptor , lymphopoiesis , natural killer t cell , immunology , antigen , genetics , gene , immune system , stem cell , haematopoiesis , genome
Summary: Intrathymic T cell development represents one of the best studied paradigms of mammalian development. Lymphoid committed precursors enter the thymus and the Notch1 receptor plays an essential role in committing them to the T cell lineages. The pre‐T cell receptor (TCR), as an autonomous cell signaling receptor, commits cells to the αβ lineage while its rival, the γδTCR, is involved in generating the γδ lineage of T cells. Positive and negative selection of immature αβTCR‐expressing cells are essential mechanisms for generating mature T cells, committing them to the CD4 and CD8 lineages and avoiding autoimmunity. Additional lineages of αβT cells, such as the natural killer T cell lineage and the CD25 + regulatory T cell lineage, are formed when the αβTCR encounters specific ligands in suitable microenvironments. Thus, positive selection and receptor‐instructed lineage commitment represent a hallmark of the thymus. Ectopically expressed organ‐specific antigens contribute to thymic self–nonself discrimination, which represents an essential feature for the evolutionary fitness of mammalian species.