title: [Development of the thymus and immune system].
abstract: A repertoire of T cells is primarily formed in the thymus through positive and negative selection of developing thymocytes. The medullary region of the thymus provides a microenvironment that is essential for the establishment of self-tolerance via the depletion of self-reactive T cells and the production of regulatory T cells. Within the medullary microenvironment, medullary thymic epithelial cells play a pivotal role in the establishment of self-tolerance, via the promiscuous expression of tissue-restricted self-antigens and the chemokine-mediated attraction of positively selected T cells from the cortex to the medulla. Positive selection also induces the expression of TNF-superfamily cytokines and thereby nurtures the growth and development of medullary thymic epithelial cells. We will review the mechanisms of how the thymus contributes to the development and selection of T cells, with emphasis on the establishment of self-tolerance in the thymic medulla.
authors: Department of Neurology, Institute of Health Biosciences, University of Tokushima, Tokushima, Japan.
authors: Naoko
authors: N
authors: Matsui
authors: Takeshi
authors: T
authors: Nitta
authors: Yousuke
authors: Y
authors: Takahama
mesh_terms: D006801:Humans; D009157:Myasthenia Gravis / Q000276:immunology; D017634:Self Tolerance / Q000276:immunology*; D013601:T-Lymphocytes / Q000502:physiology; D013950:Thymus Gland / Q000276:immunology*