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Inducible costimulator promotes helper T-cell differentiation through phosphoinositide 3-kinase.

ABSTRACT: The T-cell costimulatory receptors, CD28 and the inducible costimulator (ICOS), are required for the generation of follicular B helper T cells (T(FH)) and germinal center (GC) reaction. A common signal transducer used by CD28 and ICOS is the phosphoinositide 3-kinase (PI3K). Although it is known that CD28-mediated PI3K activation is dispensable for GC reaction, the role of ICOS-driven PI3K signaling has not been defined. We show here that knock-in mice that selectively lost the ability to activate PI3K through ICOS had severe defects in T(FH) generation, GC reaction, antibody class switch, and antibody affinity maturation. In preactivated CD4(+) T cells, ICOS delivered a potent PI3K signal that was critical for the induction of the key T(FH) cytokines, IL-21 and IL-4. Under the same settings, CD28 was unable to activate PI3K but supported a robust secondary expansion of T cells. Thus, our results demonstrate a nonredundant function of ICOS-PI3K pathway in the generation of T(FH) and suggest that CD28 and ICOS play differential roles during a multistep process of T(FH) differentiation.

SUBMITTER: Gigoux M

PROVIDER: S-EPMC2787139 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Inducible costimulator promotes helper T-cell differentiation through phosphoinositide 3-kinase.

Gigoux Mathieu M Shang Jijun J Pak Youngshil Y Xu Minghong M Choe Jongseon J Mak Tak W TW Suh Woong-Kyung WK

Proceedings of the National Academy of Sciences of the United States of America 20091113 48

The T-cell costimulatory receptors, CD28 and the inducible costimulator (ICOS), are required for the generation of follicular B helper T cells (T(FH)) and germinal center (GC) reaction. A common signal transducer used by CD28 and ICOS is the phosphoinositide 3-kinase (PI3K). Although it is known that CD28-mediated PI3K activation is dispensable for GC reaction, the role of ICOS-driven PI3K signaling has not been defined. We show here that knock-in mice that selectively lost the ability to activa ...[more]

PMID: 19915142

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Project description:The liver capacity to recover from acute liver injury is a critical factor in the development of acute liver failure (ALF) caused by viral infections, ischemia/reperfusion or drug toxicity. Liver healing requires the switching of pro-inflammatory monocyte-derived macrophages(MoMFs) to a reparative phenotype. However, the mechanisms involved are still incompletely characterized. In this study we investigated the contribution of T-lymphocyte/macrophage interaction through the co-stimulatory molecule Inducible T-cell co-stimulator (ICOS; CD278) and its ligand (ICOSL; CD275) in modulating liver repair. The role of ICOS/ICOSL dyad was investigated during the recovery from acute liver damage induced by a single dose of carbon tetrachloride (CCl4). Flow cytometry of non-parenchymal liver cells obtained from CCl4-treated wild-type mice revealed that the recovery from acute liver injury associated with a specific up-regulation of ICOS in CD8+ T-lymphocytes and with an increase in ICOSL expression involving CD11bhigh/F4-80+ hepatic MoMFs. Although ICOS deficiency did not influence the severity of liver damage and the evolution of inflammation, CCl4-treated ICOS knockout (ICOS-/- ) mice showed delayed clearance of liver necrosis and increased mortality. These animals were also characterized by a significant reduction of hepatic reparative MoMFs due to an increased rate of cell apoptosis. An impaired liver healing and loss of reparative MoMFs was similarly evident in ICOSL-deficient mice or following CD8+ T-cells ablation in wild-type mice. The loss of reparative MoMFs was prevented by supplementing CCl4-treated ICOS-/- mice with recombinant ICOS (ICOS-Fc) which also stimulated full recovery from liver injury. These data demonstrated that CD8+ T-lymphocytes play a key role in supporting the survival of reparative MoMFs during liver healing trough ICOS/ICOSL-mediated signaling. These observations open the possibility of targeting ICOS/ICOSL dyad as a novel tool for promoting efficient healing following acute liver injury.

Dataset Information

Inducible costimulator promotes helper T-cell differentiation through phosphoinositide 3-kinase.

Publications

Inducible costimulator promotes helper T-cell differentiation through phosphoinositide 3-kinase.

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