Regulatory T cells (Tregs) expressing the Foxp3 transcription factor are indispensable for the maintenance of immune system homeostasis. Tregs may lose Foxp3 expression or be reprogrammed into cells that produce proinflammatory cytokines, for example, Th1-like Tregs, Th2-like Tregs, Th17-like Tregs, and Tfh-like Tregs. Accordingly, selective therapeutic molecules that manipulate Treg lineage stability and/or functional activity might have the potential to improve aberrant immune responses in human disorders. In particular, the transcription factor Helios has emerged as an important marker and modulator of Tregs. Therefore, the current review focuses on recent findings on the expression, function, and mechanisms of Helios, as well as the patterns of Foxp3⁺ Tregs coexpressing Helios in various human disorders, in order to explore the potential of Helios for the improvement of many immune-related diseases. The studies were selected from PubMed using the library of the Nanjing Medical University in this review. The findings of the included studies indicate that Helios expression stabilizes the phenotype and function of Foxp3⁺ Tregs in certain inflammatory environments. Further, Tregs coexpressing Helios and Foxp3 were identified as a specific phenotype of stronger suppressor immune cells in both humans and animal models. Importantly, there is ample evidence that Helios-expressing Foxp3⁺ Tregs are relevant to various human disorders, including connective tissue diseases, infectious diseases, solid organ transplantation-related immunity, and cancer. Thus, Helios⁺Foxp3⁺CD4⁺ Tregs could be a valuable target in human diseases, and their potential should be explored further in the clinical setting.

The shortage of dc protection device limits the development of dc grids. This letter proposes a novel superconducting magnetic energy storage (SMES)-based transformerless series voltage restorer (TLSVR) for dc-load protections. The proposed SMES-TLSVR is made up mainly of a bidirectional-switch-based converter and a superconducting coil, and is interfaced in the series with the dc transmission line. It has the advantages of duplex voltage compensation ability, transformerless structure, and swift compensation response, and has a wider compensation range than traditional voltage-fed transformerless dynamic voltage restorer. The topology, circuit principle, and control strategy are elaborated in this letter. Finally, a kW-class SMES prototype is carried out to verify the feasibility of the proposed SMES-TLSVR.

The limitation of theDC protection device confines the development of MV/LVDC grids. This paper presents a DC dynamic voltage restorer to exploit DC custom power devices for DC distribution networks in principle. It is based on an improved AC/DC dual active bridge and battery energy storage to maintain the voltage profile of sensitive loads in DC networks. The principle of the improved DC-DVR has been analyzed from the perspectives of the range of compensated voltage, current characteristics, and control strategy. Compared with other existing methods, the proposed DC-DVR features a simple structure, an easy control strategy, and the ability to mitigate both voltage sag and swell by injecting forward or reverse voltage. Experiment results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure. A case study of DC doubly-fed induction generator (DFIG) interfaced with power grid is carried out, integrated with the proposed DC-DVR to verify the operation principle of the proposed scheme.

In this article, the superconducting fault current limiter (SFCL) explores its relatively new application: the power electronic circuit. The investigation of this compact-size SFCL involves both the experiments and numerical modelling. A bifilar-shape resistive-type SFCL was used in a DC-DC power conversion circuit, for the purpose of suppressing the overwhelming fault current by 3 different types of faults: the input fault, output fault, and switch fault. The numerical modelling of SFCL used an electromagnetic-thermal coupled finite-element method (FEM) model based on the H -formulation. For these 3 types of faults with the 100 ms fault duration, good agreement was found between the experiments and simulations. Both the experiment and modelling method were used to test the SFCL performance with different fault durations (50 ms vs 100 ms). For some severe fault conditions (e.g., higher fault current and longer fault duration) that experiments were difficult or unable to realise, the FEM modelling of SFCL was used to simulate the performance. Overall, the FEM modelling of SFCL can well match the SFCL experiment, and has the advantage of showing more information such as the current distribution and temperature. Both the SFCL experiments and numerical modelling offer new results and novel concepts of SFCL investigation, which can be helpful for the design of future SFCLs and the compact protection schemes for power electronic devices.