International Immunology, Vol 9, 1253-1258, Copyright © 1997 by Oxford University Press
RN Cahill, WG Kimpton, EA Washington, L Dudler and Z Trnka
Lymphocyte recirculation is critical to maximize the efficiency of
immunological surveillance and is an absolute requirement for the
development of systemic memory. The consensus view of the lifespan of
peripheral T cells holds that naive T cells are long-lived cells and most
memory T cells are short-lived cells, although the question of the lifespan
of peripheral T cells is not yet fully resolved. We have studied the
lifespan of T cells circulating in efferent lymph draining lymph nodes (LN)
in the immunologically naive sheep fetus and in postnatal lambs immediately
following birth by examining the in vivo incorporation of [3H]thymidine by
newly formed T cells during continuous administration of [3H]thymidine. We
report that authentically naive fetal T cells are long-lived cells which
continue to recirculate between blood and lymph during fetal life. At
birth, however, a process is triggered whereby fetal T cells circulating
through LN are rapidly lost from the peripheral T cell pool and are
replaced by freshly arriving T cells which have been formed since birth.
Our results indicate that by the end of the first week of postnatal life,
around three-quarters of the T cells circulating through peripheral LN have
been formed since birth.
ARTICLES
An immune system switch in T cell lifespan at birth results in extensive loss of naive fetal T cells during the first week of postnatal life
Laboratory for Fetal and Neonatal Immunology, University of Melbourne, Parkville, Victoria, Australia.
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