Inducible Costimulator Expression Regulates the Magnitude of Th2-Mediated Airway Inflammation by Regulating the Number of Th2 Cells

Inducible Costimulator (ICOS) is an important regulator of Th2 lymphocyte function and a potential immunotherapeutic target for allergy and asthma. A SNP in the ICOS 5' promoter in humans is associated with increased atopy and serum IgE in a founder population and increased ICOS surface expression and Th2 cytokine production from peripheral blood mononuclear cells. However, it is unknown if increased ICOS expression contributes to disease progression or is a result of disease pathology.We developed a mouse model in which ICOS surface expression levels are genetically predetermined to test our hypothesis that genetic regulation of ICOS expression controls the severity of Th2 responses in vivo. Using ICOS+/+ and ICOS+/- mice in a Th2 model of airway inflammation, we found that T cells from the ICOS+/- mice had reduced ICOS expression and decreased Th2-mediated inflammation in vivo. Although the activation status of the T cells did not differ, T cells isolated from the lungs and draining lymph nodes of ICOS+/- mice at the peak of inflammation produced less Th2 cytokines upon stimulation ex vivo. Using 4get mice, which express GFP upon IL-4 transcription, we determined that the decreased Th2 cytokines in ICOS+/- is due to reduced percentage of Th2 cells and not a defect in their ability to produce IL-4.These data suggest that in both mice and humans, the level of ICOS surface expression regulates the magnitude of the in vivo Th2 response, perhaps by influencing Th2 differentiation

Multi-omics: Differential expression of IFN-γ results in distinctive mechanistic features linking chronic inflammation, gut dysbiosis, and autoimmune diseases

Low grade, chronic inflammation is a critical risk factor for immunologic dysfunction including autoimmune diseases. However, the multiplicity of complex mechanisms and lack of relevant murine models limit our understanding of the precise role of chronic inflammation. To address these hurdles, we took advantage of multi-omics data and a unique murine model with a low but chronic expression of IFN-γ, generated by replacement of the AU-rich element (ARE) in the 3’ UTR region of IFN-γ mRNA with random nucleotides. Herein, we demonstrate that low but differential expression of IFN-γ in mice by homozygous or heterozygous ARE replacement triggers distinctive gut microbial alterations, of which alteration is female-biased with autoimmune-associated microbiota. Metabolomics data indicates that gut microbiota-dependent metabolites have more robust sex-differences than microbiome profiling, particularly those involved in fatty acid oxidation and nuclear receptor signaling. More importantly, homozygous ARE-Del mice have dramatic changes in tryptophan metabolism, bile acid and long-chain lipid metabolism, which interact with gut microbiota and nuclear receptor signaling similarly with sex-dependent metabolites. Consistent with these findings, nuclear receptor signaling, encompassing molecules such as PPARs, FXR, and LXRs, was detectable as a top canonical pathway in comparison of blood and tissue-specific gene expression between female homozygous vs heterozygous ARE-Del mice. Further analysis implies that dysregulated autophagy in macrophages is critical for breaking self-tolerance and gut homeostasis, while pathways interact with nuclear receptor signaling to regulate inflammatory responses. Overall, pathway-based integration of multi-omics data provides systemic and cellular insights about how chronic inflammation driven by IFN-γ results in the development of autoimmune diseases with specific etiopathological features

Inducible Costimulator Expression Regulates the Magnitude of Th2-Mediated Airway Inflammation by Regulating the Number of Th2 Cells

Background: Inducible Costimulator (ICOS) is an important regulator of Th2 lymphocyte function and a potential immunotherapeutic target for allergy and asthma. A SNP in the ICOS 5′ promoter in humans is associated with increased atopy and serum IgE in a founder population and increased ICOS surface expression and Th2 cytokine production from peripheral blood mononuclear cells. However, it is unknown if increased ICOS expression contributes to disease progression or is a result of disease pathology.Methodology/Principal Findings: We developed a mouse model in which ICOS surface expression levels are genetically predetermined to test our hypothesis that genetic regulation of ICOS expression controls the severity of Th2 responses in vivo. Using ICOS+/+ and ICOS+/− mice in a Th2 model of airway inflammation, we found that T cells from the ICOS+/− mice had reduced ICOS expression and decreased Th2-mediated inflammation in vivo. Although the activation status of the T cells did not differ, T cells isolated from the lungs and draining lymph nodes of ICOS+/− mice at the peak of inflammation produced less Th2 cytokines upon stimulation ex vivo. Using 4get mice, which express GFP upon IL-4 transcription, we determined that the decreased Th2 cytokines in ICOS+/− is due to reduced percentage of Th2 cells and not a defect in their ability to produce IL-4.Conclusion: These data suggest that in both mice and humans, the level of ICOS surface expression regulates the magnitude of the in vivo Th2 response, perhaps by influencing Th2 differentiation.</p

ICOS^+/− T cells have decreased ICOS expression but equal activation status.

<p>ICOS^+/+ (black lines) and ICOS^+/− (grey line) T cells were isolated and stimulated with anti-CD3 and anti-CD28 antibodies in media alone or in the presence of IL-4 or anti-IL-4 antibodies. After 48 hours the cells were removed and expression of the indicated surface markers were analyzed via flow cytometry. (A) ICOS expression on CD4⁺ T cells stimulated under the indicated conditions. (B) Expression of the indicated cell-surface markers after stimulation for 48 hours in media alone cultures.</p

Decreased Th2 response in B7RP-1^+/− mice.

<p>Splenocytes from Wild-type and B7RP-1^+/− mice were removed and single-cell suspensions were made. The cells were stained with B7RP-1 and either CD19 or CD11c. Black = WT Grey = B7RP-1^+/−. (B) B6. B7RP-1^+/+ (black bars), B6. B7RP-1^+/− (grey bars), and B6. B7RP-1^−/− (white bars) mice were sensitized and challenged as indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007525#s2" target="_blank">Materials and Methods</a>. Total cells in BAL fluid were counted and percent CCR3⁺ eosinophils, CD4⁺ T cells and CD8⁺ T cells were analyzed via flow cytometry and used to calculate total cell numbers and normalized to the average of the wild-type value. ICOS expression on BAL CD4⁺ T cells isolated from the mediastinal lymph nodes of mice is shown. Serum IgE levels were analyzed via ELISA.</p