Thymic T-Cell Selection

{
  "id": "MLC-T-ENV-028056",
  "term": "Thymic T-Cell Selection",
  "field": "Environment",
  "definition": "Bone marrow-derived stem cells in the thymus become educated to recognize complexes of self-major histocompatibility complex (MHC) molecules plus self-peptides in a process called positive selection under the influence of epithelial cells in the thymic cortex. Positively-selected thymic T cell precursors (thymocytes) then progress through a process called negative selection under the influence of bone marrow-derived dendritic cells at the corticomedullary junction where self-reactive, and potentially autoimmunity-inducing, thymocytes are deleted. Thymocytes simultaneously progress through phases expressing both CD4 and CD8 coreceptors to a single positive stage expressing only CD4 or CD8 in addition to the T cell receptor. They are then allowed to leave the thymus and enter the periphery via the lymphatics or venules of the circulatory system as mature T cells.",
  "references": [
    "National Cancer Institute Thesaurus"
  ],
  "url": "https://mlchart.com/terminology/environment/thymic-t-cell-selection/"
}