The generation and fate of thymocytes.
In the adult thymus the majority of thymocytes are at a non-proliferating end stage, during which 3% of all CD4+CD8+ cortical thymocytes are selected on the basis of appropriate T-cell antigen-receptor (TcR) specificity to become CD4-CD8+ or CD4+CD8- mature thymocytes. The selected mature cells gradually emigrate to the periphery. The 97% unselected, or positively rejected, CD4+CD8+ thymocytes die in the thymus. This 3-day end stage is, however, the product of around 2 weeks of proliferation by less mature thymocytes, which gives about a 10(5)-fold expansion from the hundred prothymocytes estimated to seed the thymus each day. Rearrangement and expression of TcR genes and a sequence of changes in surface antigens occurs during this prolonged period. Two sequential waves of expansion and differentiation appear to be involved. The first, about 1 week long, involves the less than 0.1% of thymocytes which still resemble the prothymocyte; this leads via a non-dividing interval to the second 1-week stage involving the 3% of CD4-CD8- thymocytes and then the CD4+CD8+ blasts.
Shortman
K
K
Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia.
Egerton
M
M
Spangrude
G J
GJ
Scollay
R
R
D000818:Animals; D016923:Cell Death; D002454:Cell Differentiation; D002455:Cell Division; D002465:Cell Movement; D008213:Lymphocyte Activation / Q000502:physiology; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
D011948:Receptors, Antigen, T-Cell