T Cell Development in the Human Thymus
T cell differentiation occurs in the thymus. In the thymus CD4+ helper cells and CD8αβ+ cytotoxic cells are generated under tight MHC control. Besides intrathymic T cell generation, T cells are generated outside the thymus. Peripheral expansion of mature T cells, which may or may not be antigen driven, is a major source of peripheral T cells, as well as de novo formation of T cells. Extrathymic T cell development mainly gives rise to CD4-CD8 double negative or CD8αα+TCRαβ+ and TCRγδ+ cells which reside mainly in bone marrow and epithelia.
KeywordsSevere Combine Immunodeficiency Double Positive Human Thymus Fetal Thymus Genetically Engineer Mouse
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