Background. Growth arrest-specific (Gas) 6 is one of the endogenous ligands of TAM receptors (Tyro3, Axl, and Mertk), and its role as an immune modulator has been recently emphasized. Naturally occurring CD4+CD25+ regulatory T cells (Tregs) are essential for the active suppression of autoimmunity. The present study was designed to investigate whether Tregs express TAM receptors and the potential role of Gas6-TAM signal in regulating the suppressive function of Tregs. Methods. The protein and mRNA levels of TAM receptors were determined by using Western blot, immunofluorescence, flow cytometry, and RT-PCR. Then, TAM receptors were silenced using targeted siRNA or blocked with specific antibody. The suppressive function of Tregs was assessed by using a CFSE-based T cell proliferation assay. Flow cytometry was used to determine the expression of Foxp3 and CTLA4 whereas cytokines secretion levels were measured by ELISA assay. Results. Tregs express both Axl and Mertk receptors. Gas6 increases the suppressive function of Tregs in vitro and in mice. Both Foxp3 and CTLA-4 expression on Tregs are enhanced after Gas6 stimulation. Gas6 enhances the suppressive activity of Tregs mainly through Axl receptor. Conclusion. Gas6 has a direct effect on the functions of CD4+CD25+Tregs mainly through its interaction with Axl receptor.

Acute kidney injury (AKI) is a serious complication of sepsis, which has a high mortality rate. Growth arrest-specific protein 6 (Gas6), the protein product of the growth arrest specific gene 6, has been shown to have an anti-apoptotic effect as well as pro-survival capability. Here, we investigated the effects of Gas6 on sepsis-associated AKI in mice subjected to cecal ligation and puncture (CLP). We found that the administration of rmGas6 significantly reduced serum urea nitrogen and creatinine and improved the survival of septic mice. Furthermore, the renal pathological damage induced by CLP was attenuated by rmGas6 treatment. Finally, rmGas6 reduced the renal tissue apoptotic index and the expression of Bax, while it upregulated the expression of Bcl-2. The data suggest that rmGas6 might be used as a potential therapeutic agent for sepsis-induced AKI.

Immune dysfunction contributes to secondary infection and worse outcomes in sepsis. Regulatory T cells (Tregs) have been implicated in sepsis-induced immunosuppression. Nevertheless, the role of Tregs in secondary infection after sepsis remains to be determined. In the present study, a two-hit model which mimics clinical conditions was used and the potential role of Tregs in secondary Pseudomonas aeruginosa infection post-sepsis was investigated. Results showed that mice were susceptible to secondary P. aeruginosa infection 3 days, but not 7 days, post-cecal ligation and puncture (CLP). The levels of IL-17A, IL-1β, and IL-6 remained low in CLP mice after P. aeruginosa infection, while the levels of IL-10 increased significantly. Additionally, increased number of Tregs in both lung and spleen was observed in "two-hit" mice. Injection with PC61 (anti-CD25) mAb reduced the number of Tregs by 50% in spleen and 60% in lung of septic mice. This partial depletion of Tregs elevated IL-17A, IL-1β, and IL-6 production and decreased IL-10 levels in septic mice with P. aeruginosa infection, leading to lower bacterial load, attenuation of lung injury, and improvement of survival. The present findings demonstrate that Tregs play a crucial role in secondary P. aeruginosa infection after sepsis by modulating the inflammatory response.

Background Liver abscess is a common emergency in the emergency department. However, cerebral venous sinus thrombosis (CVST) is a rare and serious cerebrovascular disease. Cases of CVST in patients with Klebsiella pneumoniae primary liver abscess (KLA) have not been described in the literature. We report a case of CVST in patients with KLA. Case presentation A 54-year-old male patient came to our department with a fever for 2 days and altered mental status for 1 day. Abdominal computed tomography (CT) and liver magnetic resonance imaging (MRI) revealed multiple liver abscesses. The blood culture was identified as Klebsiella pneumoniae sepsis. Head contrast-enhanced MRI and magnetic resonance venography (MRV) imaging showed multiple thrombus formation in the right transverse sinus and sigmoid sinus. The patient's infection and thrombosis were controlled within one week of multidisciplinary comprehensive treatment such as antibiotic and antithrombotic therapy, and a good clinical recovery during the 1-month follow-up. Conclusion CVST after liver abscess is rare, clinicians should be aware of this complication and vigilant for the possibility of bacterial meningitis. The underlying mechanisms need to be further studied.