Related Experiment Videos
T cell apoptosis by kynurenines.
Francesca Fallarino1, Ursula Grohmann, Carmine Vacca
1Department of Experimental Medicine, University of Perugia, Italy. fllfnc@tin.it
Advances in Experimental Medicine and Biology
|June 23, 2004
Summary
Indoleamine 2,3-dioxygenase (IDO) regulates T cells by depleting tryptophan. Its metabolites induce selective T cell apoptosis, suggesting a role in immune tolerance.
Area of Science:
- Immunology
- Biochemistry
Background:
- Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-catabolizing enzyme influencing T cell regulation.
- IDO activity is hypothesized to protect fetal allografts from maternal immune rejection.
Purpose of the Study:
- To investigate the mechanisms of IDO-dependent immune regulation.
- To explore the role of tryptophan metabolites in T cell apoptosis and immune tolerance.
Main Methods:
- In vitro apoptosis assays using thymocytes and T cell subsets (Th1, Th2) with kynurenine pathway metabolites.
- Analysis of caspase-8 activation and cytochrome c release.
- In vivo studies assessing thymocyte subset depletion.
Main Results:
- Kynurenine pathway metabolites (3-hydroxyanthranilic and quinolinic acids) induced selective apoptosis of murine thymocytes and Th1 cells in vitro.
- Apoptosis occurred at low kynurenine concentrations, independent of Fas/Fas ligand, and involved caspase-8 and mitochondrial pathways.
- In vivo, these kynurenines depleted specific thymocyte subsets, similar to dexamethasone.
Conclusions:
- Tryptophan catabolism via the kynurenine pathway can directly induce T cell apoptosis.
- These findings provide evidence for the involvement of tryptophan catabolism in regulating T cell apoptosis and maintaining peripheral T cell tolerance.