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Thymic T cell export is not influenced by the peripheral T cell pool
M J Gabor1, R Scollay, D I Godfrey
1Centenary Institute of Cancer Medicine and Cell Biology, Sydney, Australia.
European Journal of Immunology
|December 12, 1997
Summary
The thymus does not change its T cell output even when peripheral T cells are depleted. Thymic T cell export appears to be internally regulated, independent of peripheral T cell numbers or ratios.
Area of Science:
- Immunology
- T cell biology
- Thymic research
Background:
- The peripheral T cell pool relies on thymus output and post-thymic expansion.
- The thymus's ability to adjust T cell output after peripheral depletion is unknown.
Purpose of the Study:
- To investigate if the thymus alters its T cell output in response to peripheral T cell depletion.
- To determine if thymic output changes in number or CD4:CD8 ratio following peripheral T cell reduction.
Main Methods:
- Intrathymic injection of fluorescein isothiocyanate to label recent thymic emigrants (RTE).
- In vivo depletion of peripheral T cells using anti-Thy-1 or anti-CD4 antibodies.
- Analysis of RTE number, cell cycle status, and CD4:CD8 ratio in peripheral lymphoid organs.
Main Results:
- Depleting over 70% of peripheral T cells did not alter RTE number or cell cycle status.
- Depleting CD4 T cells did not change the total number or CD4+ CD8- RTE proportion in peripheral organs.
- The CD4:CD8 ratio in the periphery was significantly reduced without affecting thymic output.
Conclusions:
- Thymic output is not influenced by peripheral T cell pool size or CD4:CD8 ratio.
- Thymic T cell export is likely regulated by intrinsic mechanisms within the thymus.