HTHSCI 3I03 Chapter Notes - Chapter 9: Thymocyte, Bone Marrow, Mhc Restriction
24 Mar 2015
School
Department
Course
Professor
Document Summary
The thymus is divided into 4 regions (from top to bottom): the subcapsular region, the cortex, the cortico-medullary junction, and the medulla. Cells of the cortex: cortical epithelial cells, sub-capsular epithelial cells, thymocytes (originate from the bone marrow) Cells of the medulla: medullary epithelial cells, dendritic cells (originate from the bone marrow, macrophages (originate from the bone marrow, hasall"s corpuscles (direct maturation of dcs) There are 108 thymocytes in the thymus. Thus, 98% of thymocytes die within the thymus! 5 x 107 new thymocytes are generated daily. T cell progenitors develop in the bone marrow and migrate to the thymus. The t cell precursor rearranges tcr genes in the thymus. T cells mature from double negative thymocytes, to double positive thymocytes, and then finally to single positive thymocytes: double negative (cd3-/cd4-/cd8-); in subcapsular region, double positive (cd3+/cd4+/cd8+); in cortex, single positive (cd3+/cd4+/cd8- or cd3+/cd4-/cd8+); in medulla.
