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SUMMARY:LYMPHOPOIESIS IN THE FOETUS AND NEONATE - Dr Wayne Kimpton\, Labor
 atory for Foetal and Neonatal Immunology\, Faculty of Veterinary Science\,
  University of Melbourne\, Australia
DTSTART:20071010T153000Z
DTEND:20071010T163000Z
UID:TALK8206@talks.cam.ac.uk
CONTACT:Laurence Tiley
DESCRIPTION:The foetus develops in a protected intrauterine environment wh
 ere the onus is largely on non responsiveness.  At birth a major physiolog
 ical event occurs whereby the newborn undergoes a transition from its prot
 ected environment to one where pathogenic organisms are encountered for th
 e first time and protection is vital. Considering the importance of neonat
 al immune competency in influencing predisposition to infection and possib
 ly allergies surprisingly little attention has been paid to how the immune
  system adapts to these changed circumstances.\nIn the foetus and neonate 
 the naïve T cell pool rapidly expands as the animals grow but the mechani
 sms that regulate this T cell homeostasis are poorly understood.  Using th
 e tracking dye CFSE in vivo in combination with flow cytometry we have bee
 n able to measure the phenotypes and number of T cells exported from the f
 oetal and neonatal lamb thymus and their distribution and lifespan in peri
 pheral tissues.  This has been coupled to peripheral T cell division using
  whole body or site specific labelling of T cells with BrdU and death of c
 ells as measured by using Annexin V.\nMajor differences were found in the 
 rate of thymic export and homing specificities of distinct |T cells subset
 s during foetal and neonatal life. Moreover the numbers of T cells produce
 d each day by thymic export and substantial clonal expansion in peripheral
  lymphoid tissues in both the foetus and neonate were well in excess of th
 ose needed for the growth of the peripheral T cell pool.  Our results show
  that newly produced T cells (particulary those in the recirculating T cel
 l pool) have an extremely short lifespan\, and are replaced by fresh waves
  of clonally expanding thymic emigrants. Continuous displacement of short-
 lived naïve recirculating T cell populations by clonally expanding thymic
  emigrants is likely to confer an important survival advantages on the neo
 nate through the regular reconstitution of a substantial portion of the na
 ïve peripheral T cell repertoire for antigen.\n
LOCATION:Lecture Theatre 1\, Department of Veterinary Medicine
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