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Human recent thymic emigrants--identification, expansion, and survival characteristics
1Children's Research Centre, Our Lady's Hospital for Sick Children, Dublin, Ireland. jaythoon.hassan@ucd.ie
Journal of Immunology (Baltimore, Md. : 1950)
|August 8, 2001
Summary
Newly born humans have T cells, called recent thymic emigrants (RTEs), that can grow and survive without antigens. These RTEs maintain their T cell receptor repertoire, unlike mature T cells.
Area of Science:
- Immunology
- T cell biology
- Developmental immunology
Background:
- Circulating T cells in newborns are identified as recent thymic emigrants (RTEs).
- RTEs exhibit high expression of TCR excision circles and thymocyte-like apoptosis rates.
Purpose of the Study:
- To investigate the characteristics and behavior of RTEs in early life.
- To determine the role of common gamma-chain cytokines, like IL-7, in RTE survival and proliferation.
Main Methods:
- Analysis of TCR excision circle levels in human neonatal T cells.
- Assessment of apoptosis rates and cytokine responses (IL-7) in RTEs and adult naive T cells.
- Evaluation of recombination-activating gene-2 expression in vitro.
Main Results:
- RTEs display enhanced survival, cell cycle entry, and proliferation in response to IL-7.
- Mature adult naive T cells are refractory to IL-7-induced expansion.
- RTEs do not reinduce recombination-activating gene-2 expression after thymic emigration.
Conclusions:
- Postthymic naive T cells in early life are RTEs in a unique ontogenic stage.
- RTEs can undergo antigen-independent homeostatic regulation, including expansion and survival.
- RTEs maintain their preselected T cell receptor repertoire during this stage.