Reverse signaling through GITR ligand enables dexamethasone to activate IDO in allergy


Glucocorticoid-induced tumor necrosis factor receptor (GITR) on T cells and its natural ligand, GITRL, on accessory cells contribute to the control of immune homeostasis. Here we show that reverse signaling through GITRL after engagement by soluble GITR initiates the immunoregulatory pathway of tryptophan catabolism in mouse plasmacytoid dendritic cells, by means of noncanonical NF-κB–dependent induction of indoleamine 2,3-dioxygenase (IDO). The synthetic glucocorticoid dexamethasone administered in vivo activated IDO through the symmetric induction of GITR in CD4+ T cells and GITRL in plasmacytoid dendritic cells. The drug exerted IDO-dependent protection in a model of allergic airway inflammation. Modulation of tryptophan catabolism via the GITR-GITRL coreceptor system might represent an effective therapeutic target in immune regulation. Induction of IDO could be an important mechanism underlying the anti-inflammatory action of corticosteroids.

DOI: 10.1038/nm1563
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@article{Grohmann2007ReverseST, title={Reverse signaling through GITR ligand enables dexamethasone to activate IDO in allergy}, author={Ursula Grohmann and Claudia Volpi and Francesca Fallarino and Silvia Bozza and Roberta Bianchi and Carmine Vacca and Ciriana Orabona and Maria Laura Belladonna and Emira M Ayroldi and Giuseppe Nocentini and Louis Boon and Francesco Bistoni and Maria Cristina Fioretti and Luigina Romani and Carlo Riccardi and Paolo Puccetti}, journal={Nature Medicine}, year={2007}, volume={13}, pages={579-586} }