iNKT cell development is orchestrated by different branches of TGF-β signaling

Invariant natural killer T (iNKT) cells constitute a distinct subset of T lymphocytes exhibiting important immune-regulatory functions. Although various steps of their differentiation have been well characterized, the factors controlling their development remain poorly documented. Here, we show that TGF-β controls the differentiation program of iNKT cells. We demonstrate that TGF-β signaling carefully and specifically orchestrates several steps of iNKT cell development. In vivo, this multifaceted role of TGF-β involves the concerted action of different pathways of TGF-β signaling. Whereas the Tif-1γ branch controls lineage expansion, the Smad4 branch maintains the maturation stage that is initially repressed by a Tif-1γ/Smad4-independent branch. Thus, these three different branches of TGF-β signaling function in concert as complementary effectors, allowing TGF-β to fine tune the iNKT cell differentiation program

Altered thymic differentiation and modulation of arthritis by invariant NKT cells expressing mutant ZAP70

Various subsets of invariant natural killer T (iNKT) cells with different cytokine productions develop in the mouse thymus, but the factors driving their differentiation remain unclear. Here we show that hypomorphic alleles of Zap70 or chemical inhibition of Zap70 catalysis leads to an increase of IFN-gamma-producing iNKT cells (NKT1 cells), suggesting that NKT1 cells may require a lower TCR signal threshold. Zap70 mutant mice develop IL-17-dependent arthritis. In a mouse experimental arthritis model, NKT17 cells are increased as the disease progresses, while NKT1 numbers negatively correlates with disease severity, with this protective effect of NKT1 linked to their IFN-gamma expression. NKT1 cells are also present in the synovial fluid of arthritis patients. Our data therefore suggest that TCR signal strength during thymic differentiation may influence not only IFN-gamma production, but also the protective function of iNKT cells in arthritis

Development and Function of Invariant Natural Killer T Cells Producing TH2- and TH17-Cytokines

Four distinct subsets of invariant natural killer T (NKT) cells are shown to differentiate in the thymus, then migrate to peripheral tissues where they retain their phenotypic and functional characteristics

Return and volatility spillovers in the presence of structural breaks: evidence from GCC Islamic and conventional banks

The dynamics of return and volatility spillover indices were investigated to reveal the strength and direction of transmission that occurred during a financial crisis. The focus of this study was especially placed on the 2007 US subprime mortgage crisis, the global financial crisis, the European sovereign debt crisis, and the dramatic collapse of oil prices since 2014. The paper uses the Diebold and Yilmaz (Economic Journal 119(534): 158-171, 2009, International Journal of Forecasting 28(1): 57-66, 2012) spillover index behavior. Assuming one structural break, return and volatility linkages for Islamic banks in the GCC were stronger than for conventional banks. When multiple breaks were allowed, the spillover index was found to be highly sensitive to various economic events. Overall, the findings of this study provide new insights into the behavior of the Islamic and conventional banks stock returns and volatility spillovers, which may improve investment decisions and the trading strategies portfolio of investors.Scopu

The impact of government spending on non-oil-GDP in Saudi Arabia (multiplier analysis)

This paper examines the multiplier effect of Government spending on the non-oil Saudi Arabia economic growth. We focus on non-oil GDP rather than total GDP because activity in the oil sector is mainly determined by circumstances in the international oil market. To reach this aim, we use several econometric tools as causality tests, co-integration test and structural VAR, to estimate the short- and long-run effects of government expenditures on non-oil GDP in Saudi Arabia. In this empirical investigation, we employ annual data covering the period from 1970 to 2015. Our empirical findings indicate an overall pro-growth effect of government expenditures, with significant positive fiscal multiplier in the health and agriculture sectors. By empirically assessing fiscal multipliers across diverse non-oil sectors, we perceived that variations in government expenditures are linked to same directional deviations in the growth of non-oil GDP during peak economic horizons. Especially, we find that if the economy is at a peak, we obtain suitable fiscal multipliers.We greatly appreciate the financial support by the Shiekh Al-Fouzan Saudi Macroeconomic Forecasting Chair (SMFChair), at Imam University, Riyadh, Saudi Arabia. We would especially like to thank the directors chair Dr. Khaled Almeshal for his constant and continuous encouragement during the achievement of this work.Scopu

Risk connectedness between energy and stock markets: Evidence from oil importing and exporting countries

The surmounted environmental and energy challenges have motivated this study to explore the connectedness nexus between oil/renewable energy and stock markets for oil-exporting (importing) countries. We utilize the dynamic conditional correlation (DCC-GARCH) connectedness framework to compare the connectedness of oil/ renewable energy with stock markets. Our results showcase higher total connectedness between renewable energy and stock markets. We find increased connectedness during three major pandemics (Swine Flu, EBOLA, and COVID-19). We performed a regression analysis that highlighted the impact of economic and financial uncertainties on connectedness as an additional analysis. The addition of dummy variables for three major pandemics indicates that COVID-19 significantly impacted the connectedness between oil/renewable energy and stock markets. For the robustness of our results, we employed time-varying vector autoregressions (TVP-VAR) connectedness framework to showcase that our results remain qualitatively similar and robust to different specifications. We draw useful implications for oil exporting and oil importing countries in particular, and we draft ramifications for investors, portfolio managers, policymakers, and macroprudential bodies in general

Evidence of adverse selection in automobile insurance market: A seemingly unrelated probit modelling

The present paper investigates the adverse selection problem by examining the relationship between accident occurrences and deductible choice utilizing a seemingly unrelated probit model that allows for best controls for unobserved heterogeneity and endogeneity. While this microeconometric analysis does not consider a multivariate model and considers only two types of contracts, namely, those with high and low deductibles, it does suggest important implications from applying a recursive bivariate probit. We employ new cross-sectional data on a Tunisian insurance portfolio containing 31,125 policyholders. The results support some evidence for residual adverse selection in the studied insurance portfolio. Moreover, the results suggest the presence of a wealth effect in the decision of the contract choice