No abstract

There has been more and more evidence to confirm the essential role of inflammatory processes in the development of ischemic stroke. Interleukin-21 (IL-21), the most recently discovered CD132-dependent cytokine, plays a key role in regulating inflammation. The aim of the study was to understand the association between IL-21 polymorphisms and ischemic stroke, and the effects of these polymorphisms on gene expression. Two polymorphisms in IL-21, rs907715G/A and rs4833837A/G, were identified in 278 ischemic stroke patients and 282 healthy controls. Results showed that frequencies of rs907715GA and AA genotypes were significantly increased in cases than in controls (odd ratio (OR) = 1.49, 95% confidence interval (CI): 1.01-2.14, P = 0.042; OR = 2.21, 95% CI: 1.38-3.53, P = 0.001). Similarly, rs907715A allele revealed a positive association with the disease (OR = 1.52, P = 0.001). The rs4833837A/G polymorphism did not show any correlation with ischemic stroke. We further evaluated IL-21 messenger RNA (mRNA) and protein levels in peripheral blood mononuclear cells (PBMCs) from subjects carrying different polymorphism genotypes. Results revealed that subjects carrying polymorphic rs907715GA and AA genotypes had significantly higher IL-21 mRNA levels, whereas protein level was increased only in subjects with rs907715AA genotype. Serum level of IL-21 was also significantly elevated in subjects with rs907715AA genotype. These data suggest that IL-21 polymorphism is associated with increased susceptibility to ischemic stroke possibly by upregulating gene expression.

Acute lung injury and acute respiratory distress syndrome (ARDS) are caused by rapid-onset bilateral pulmonary inflammation. We therefore investigated the potential role of interleukin (IL)-10 CD4 Tr1 cells, a regulatory T cell subset with previously identified immunosuppressive functions, in ARDS patients. We first showed that circulating Tr1 cells were upregulated in active and resolved ARDS patients compared to healthy controls and pneumonia patient controls. A significant fraction of these Tr1 cells expressed granzyme B and perforin, while most Tr1 cells did not express interferon gamma (IFN-γ), IL-4, IL-17 or FOXP3, suggesting that the effector functions of these Tr1 cells were primarily mediated by IL-10, granzyme B, and perforin. Indeed, Tr1 cells effectively suppressed CD8 T cell IFN-γ production and induced lysis of monocytes and dendritic cells in vitro. The elimination of myeloid antigen-presenting cells depended on granzyme B production. We also discovered that Tr1 cells could be identified in the bronchoalveolar lavage fluid collected from ARDS patients. All these results suggested that Tr1 cells possessed the capacity to downregulate inflammation in ARDS. In support of this, we found that ARDS patients who resolved the inflammation and survived the syndrome contained significantly higher levels of Tr1 cells than ARDS patients who succumbed to the syndrome. Overall, this report added a novel piece of evidence that ARDS could be intervened by regulatory T cell-mediated suppressive mechanisms.