An immune system switch at birth triggers a change in the lifespan of peripheral T cells.
Lymphocyte recirculation is an essential element in the integration of immune responses and is an absolute requirement for the development of systemic memory in postnatal animals. During foetal life a large pool of recirculating T cells develops and migration pathways of naive T cells to skin and peripheral tissues as well as LN are established. At birth a process is triggered whereby naive fetal T cells are rapidly lost from the circulating pool and are replaced by newly arriving T cells which have been formed since birth. At present our data suggest that the thymic export in the fetus creates a pool of long-lived naive T cells of wide diversity. The situation in neonatal lambs is more complex since the thymus is exporting large numbers of short-lived thymic emigrants which enter a peripheral T-cell population where many T cells are dividing.
Cahill
R N
RN
Laboratory for Fetal and Neonatal Immunology, The University of Melbourne, Cnr Flemington Road and Park Drive, Parkville, Victoria, 3052, Australia.
Kimpton
W G
WG
Cunningham
C P
CP
Washington
E A
EA
D000818:Animals; D000831:Animals, Newborn; D002455:Cell Division; D002465:Cell Movement; D005260:Female; D008196:Lymph / Q000166:cytology / Q000276:immunology; D051379:Mice; D011247:Pregnancy; D012756:Sheep; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013950:Thymus Gland / Q000196:embryology* / Q000254:growth & development*