Cloning and characterization of GITR ligand

Glucocorticoid-induced TNFR-related gene (GITR) participates in the immune/inflammatory response. Because GITR expression has been described in cells other than T lymphocytes, we investigated whether it also modulates acute inflammatory response. Using GITR-deficient (GITR−/−) mice, we analyzed the role of GITR in the development of carrageenan-induced lung inflammation (pleurisy) by studying several proinflammatory markers 2–8 h after carrageenan injection. When compared with GITR+/+, GITR−/− mice exhibited decreased production of turbid exudate containing a lower number of leukocytes. This was correlated with the reduction of inflammatory markers (including TNF-α, IL-1β, myeloperoxidase, inducible NO synthase, and cyclooxygenase 2) in the pleural exudate and/or in the lung. Moreover, endothelial cells expressed lower levels of adhesion molecules. In lungs of GITR+/+ mice, GITR ligand expression was not modulated during pleurisy, while that of GITR increased, as a consequence of increased infiltration by GITR-expressing cells and of GITR up-regulation in macrophages and endothelial cells. Finally, cotreatment of GITR+/+ mice with carrageenan and Fc-GITR fusion protein decreased the number of inflammatory cells (pleural macrophages and lung neutrophils) as compared with carrageenan treatment alone, confirming that GITR plays a role in the modulation of pleurisy.

Section: Gitr and Its Ligand Are Expressed In The Lungsmentioning

confidence: 55%

Proinflammatory Role of Glucocorticoid-Induced TNF Receptor-Related Gene in Acute Lung Inflammation

Cuzzocrea

Nocentini

Paola

et al. 2006

“…We and others have observed that GITR triggers NF-B activation (5,24,25). Studies of the human GITR homologue, termed activation-induced TNFR-related receptor (AITR), suggest that TRAFs can play a role downstream of GITR (26,27).…”

Section: S Ignaling Pathways Triggered By Tnfr Family Members Globallmentioning

confidence: 99%

Glucocorticoid-Induced TNF Receptor, a Costimulatory Receptor on Naive and Activated T Cells, Uses TNF Receptor-Associated Factor 2 in a Novel Fashion as an Inhibitor of NF-κB Activation

Esparza

Arch

2005

Glucocorticoid-induced TNFR (GITR) has been implicated as an essential regulator of immune responses to self tissues and pathogens. We have recently shown that GITR-induced cellular events promote survival of naive T cells, but are insufficient to protect against activation-induced cell death. However, the molecular mechanisms of GITR-induced signal transduction that influence physiologic and pathologic immune responses are not well understood. TNFR-associated factors (TRAFs) are pivotal adapter proteins involved in signal transduction pathways of TNFR-related proteins. Yeast two-hybrid assays and studies in HEK293 cells and primary lymphocytes indicated interactions between TRAF2 and GITR mediated by acidic residues in the cytoplasmic domain of the receptor. GITR-induced activation of NF-κB is blocked by A20, an NF-κB-inducible protein that interacts with TRAFs and functions in a negative feedback mechanism downstream of other TNFRs. Interestingly, in contrast with its effects on signaling triggered by other TNFRs, our functional studies revealed that TRAF2 plays a novel inhibitory role in GITR-triggered NF-κB activation.

“…Recently, it has been shown that the GITR-L is expressed at high levels on resting APC, particularly B lymphocytes (20,21). Second, the requirement for initial activation of effector cells before induction of suppressor function imposes a time constraint on when suppression can become manifest.…”

Section: Cd25mentioning

confidence: 99%

Cutting Edge: IL-2 Is Critically Required for the In Vitro Activation of CD4+CD25+ T Cell Suppressor Function

Thornton

Donovan

Piccirillo

et al. 2004

492

388

CD4+CD25+ T cells are potent immunoregulatory cells that suppress TCR-induced proliferation of CD4 and CD8 T cells in vitro by a cell contact-dependent mechanism. Addition of IL-2 or anti-CD28 abrogates CD4+CD25+-mediated suppression of proliferation and has been assumed to “break suppression.” We examined IL-2 mRNA by quantitative PCR in cocultures of mouse CD4+CD25+ and CD4+CD25− T cells. Although IL-2 gene transcription was inhibited in the presence or absence of exogenous IL-2, the addition of anti-CD28 stimulated endogenous IL-2 production. Surprisingly, transcription of IL-2 mRNA was also restored in the cocultures in the presence of anti-IL-2. These results are most compatible with a model in which CD4+CD25+ T cells do not suppress the initial activation of CD4+CD25− T cells, but mediate their suppressive effects following production of IL-2 by the responder cells resulting in both the expansion of the CD4+CD25+ T cells and the induction of their suppressor function.