Deregulated T cell activation and autoimmunity in mice lacking interleukin-2 receptor beta

CD45-mediated apoptosis and IL-2 receptor downregulation by serine proteases secreted from diarrheagenic bacteria

Most enteropathogens secrete one or more members of the serine protease autotransporters of Enterobacteriaceae (SPATE). We previously demonstrated that SPATE cleaves various O-linked glycoproteins on leukocytes, including the tyrosine phosphatase CD45RO. SPATE impairs leukocyte functions and triggers apoptosis in activated T cells in vitro. Here, we show that SPATE produced by pathogenic E. coli, Shigella , and the mouse pathogen Citrobacter rodentium cleaves not only CD45RO but also CD45 isoforms containing exons A and B. We found that the cleavage of CD45 in primary T cells from both human and murine sources correlated with decreased IL2RA (CD25) surface expression in a concentration-dependent manner. SPATE did not cleave CD25 or affect T cell activation. However, SPATE requires CD45 expression for the depletion of CD25 in activated T cells, as SPATE did not significantly impact CD25 in the Jurkat J45.01 cell line, which lacks CD45. More importantly, we discovered that J45.01 cells resisted SPATE-mediated apoptosis, whereas apoptotic wild-type Jurkat cells exhibited decreased surface expression of CD25. Furthermore, we observed that mice infected with C. rodentium lacking SPATE displayed lower mortality, delayed intestinal colonization, reduced inflammatory cytokines, and decreased leukocyte infiltration in the lamina propria while having a higher number of CD25+ T cells compared to mice infected with wild-type CR or the CR SPATE mutant expressing Crc2 in trans. Our data suggest that SPATE-producing pathogens trigger T-cell apoptosis through CD45 via a mechanism akin to IL2 deprivation, demonstrating that SPATE can act as immunomodulators at various levels of the immune system.

SIGNIFICANCE

We have demonstrated for the first time that serine proteases (C2S) from clinically relevant pathogens, such as E. coli pathotypes and Shigella , can cleave leukocyte glycoproteins, including the tyrosine phosphatase CD45, which play crucial roles in cellular and immune functions. In this study, we discovered that C2S induces apoptosis in activated T cells through a previously unknown mechanism resembling IL-2 deprivation, mediated by CD45. Furthermore, we found that C2S is essential for bacterial virulence in vivo. This suggests that pathogens producing C2S may possess previously undescribed immunoregulatory functions that enhance their survival in the host and contribute to the disease process by eliminating T cells through the targeting of CD45 and the IL-2 receptor.

Based on the immune system: the role of the IL-2 family in pancreatic disease

The IL-2 family, consisting of IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21, is a key regulator of the immune response. As an important endocrine and digestive organ, the function of the pancreas is regulated by the immune system. Studies have shown that each cytokine of the IL-2 family influences the occurrence and development of pancreatic diseases by participating in the regulation of the immune system. In this paper, we review the structural and functional characteristics of IL-2 family members, focus on their molecular mechanisms in pancreatic diseases including acute pancreatitis, chronic pancreatitis and pancreatic cancer, and highlight the importance of the related proteins in the regulation of immune response and disease progression, which will provide valuable insights for new biomarkers in pancreatic diseases, early diagnosis of the diseases, assessment of the disease severity, and development of new therapeutic regimens. The insights of the study are summarized in the following sections.

Inflammatory cytokines and carpal tunnel syndrome: A causal relationship revealed

OBJECTIVES

Carpal tunnel syndrome (CTS) and certain inflammatory cytokines have been linked in observational studies; however, the exact causative linkages remain unknown. The purpose of this study is to investigate any possible link between the onset of CTS and 91 inflammatory cytokines.

METHODS

A two-sample bidirectional Mendelian randomization (MR) approach was used in this investigation. 91 circulating inflammatory cytokines' genetic variants were retrieved from the European ancestry genome-wide association study (GWAS) database. From germline GWAS, summary data for 24,766 CTS patients and 360,538 controls were gathered. The instrumental variables were single nucleotide polymorphisms (SNPs) that were highly correlated with the 91 inflammatory cytokines. The random-effects inverse-variance weighted (IVW) approach was employed in the primary analysis, and multiple comparisons were subjected to the Bonferroni correction. Sensitivity analysis was performed to evaluate the validity of the causal relationship.

RESULTS

Our findings showed a negative correlation between CCL19, FGF-19, IL-5, TGF-alpha, TRAIL, and the risk of CTS. Specifically, CCL19 (odds ratio [OR]: 0.944, 95 % confidence interval [CI]: 0.894-0.996, p = 0.0349), FGF-19 (OR: 0.940, 95 % CI: 0.894-0.987, p = 0.0133), IL-5 (OR: 0.936, 95 % CI: 0.885-0.990, p = 0.0212), TGF-alpha (OR: 0.902, 95 % CI: 0.838-0.970, p = 0.0057), and TRAIL (OR: 0.926, 95 % CI: 0.881-0.974, p = 0.0026) were inversely related to CTS risk. Conversely, CCL20, IL-2RB, and IL-6 were positively associated with an increased risk of CTS. Specifically, CCL20 (OR: 1.072, 95 % CI: 1.005-1.142, p = 0.0334), IL-2RB (OR: 1.067, 95 % CI: 1.001-1.137, p = 0.0463), and IL-6 (OR: 1.088, 95 % CI: 1.005-1.177, p = 0.0365) were positively correlated with CTS risk. Reverse Mendelian randomization analyses indicated no evidence of a reverse causal relationship between CTS and inflammatory cytokines.

CONCLUSION

According to this study, there is a causal link between CTS and certain inflammatory cytokines, which suggests that these cytokines may be important in the pathophysiology of CTS. To confirm these results and investigate the specific function of these cytokines in the beginning and development of CTS, more investigation is necessary.

Hypothetical proteins of chicken-isolated Limosilactobacillus reuteri subjected to in silico analyses induce IL-2 and IL-10

Lactic acid bacteria (LAB) probiotics are health-promoting but their characteristics, safety profile and functional mechanisms are not fully understood. Hence, this study aimed to characterize some hypothetical proteins of the chicken-isolated Limosilactobacillus reuteri genome and unravel their IL-2 and IL-10-inducing potential to understand mechanisms of their immunological functionality for sustainable applications. The selected proteins were subjected to in silico analyses for transmembrane topology, sub-cellular localization, IL-2 and IL-10-inducing ability and IL-2 and IL-10 gene expression across various conditions. IL-2 and IL-10-inducing mutants were statistically analyzed using a one-way analysis of variance of a general linear model of SAS and statistical significance was set at p < 0.05. The analyzed proteins are stable under a wide temperature range. All the hypothetical proteins are IL-2 and IL-10-inducing but QHPv.2.12, QHPv.2.13 and QHPv.2.15 are non-immunogenic. The evaluated mutants are IL-2 and IL-10-inducers but QHPv.2.13 and QHPv.2.15 are not immunogenic. This study sheds light on understanding the functional mechanisms of chicken-isolated L. reuteri and suggests it or its proteins as potent candidates for feed additive and therapeutic purposes.

CD122 is an activation marker ensuring proper proliferation of T cells in teleost

As one of subunits for interleukin-2 receptor (IL-2R), CD122 can bind to IL-2 and then activate downstream signal transduction to participate in adaptive immune response. Although CD122 has been identified and investigated from several teleost species, studies on its function at T-cell level are still scarce for lack of specific antibodies. In this study, a typical CD122 in Nile tilapia (Oreochromis niloticus) was characterized by bioinformatics analysis, cloned to produce retrovirus infected NIH/3T3 cells for mouse immunization. After cell fusion and screening, we successfully developed a mouse anti-tilapia CD122 monoclonal antibody (mAb), which could specifically recognize CD122 and identify CD122-producing T cells of tilapia. Using the mAb to detect, CD122 was found to widely distribute in immune-related tissues, and significantly elevate post Edwardsiella piscicida infection or T-cell activation. More importantly, the expansion of CD122+ T cells and up-regulation of CD122 occurred both in total T cells and T-cell subsets during T-cell activation upon in vitro stimulation or in vivo infection. These results indicate that CD122 can be used as a T-cell activation marker in tilapia. Notably, CD122 mAb blocking blunted the activation of MAPK/Erk and mTORC1 pathways, and inhibited T-cell proliferation, suggesting a critical role of CD122 in ensuring proper proliferation of tilapia T cells. Therefore, this study enriches the knowledge of T-cell responses in fish and provides new evidence for understanding the evolution of lymphocyte-mediated adaptive immunity.

Bridging therapy-induced phenotypes and genetic immune dysregulation to study interleukin-2-induced immunotoxicology

Interleukin-2 (IL-2) holds promise for the treatment of cancer and autoimmune diseases, but its high-dose usage is associated with systemic immunotoxicity. Differential IL-2 receptor (IL-2R) regulation might impact function of cells upon IL-2 stimulation, possibly inducing cellular changes similar to patients with hypomorphic IL2RB mutations, presenting with multiorgan autoimmunity. Here, we show that sustained high-dose IL-2 stimulation of human lymphocytes drastically reduces IL-2Rβ surface expression especially on T cells, resulting in impaired IL-2R signaling which correlates with high IL-2Rα baseline expression. IL-2R signaling in NK cells is maintained. CD4+ T cells, especially regulatory T cells are more broadly affected than CD8+ T cells, consistent with lineage-specific differences in IL-2 responsiveness. Given the resemblance of cellular characteristics of high-dose IL-2-stimulated cells and cells from patients with IL-2Rβ defects, impact of continuous IL-2 stimulation on IL-2R signaling should be considered in the onset of clinical adverse events during IL-2 therapy.

IL-2 based cancer immunotherapies: an evolving paradigm

Discovered over 4 decades ago in the supernatants of activated T cells, interleukin-2 (IL-2) is a potent pleiotropic cytokine involved in the regulation of immune responses. It is required for effector T cell expansion and differentiation as well as for peripheral tolerance induced by regulatory T cells. High-dose IL-2 treatment was the first FDA-approved immunotherapy for renal cell carcinoma and melanoma, achieving single agent complete and durable responses, albeit only in a small proportion of patients. The therapeutic potential of wild type IL-2 is clinically limited by its short half-life and severe vascular toxicity. Moreover, the activation of regulatory T cells and the terminal differentiation of effector T cells on IL-2 pose additional restrictions. To overcome the toxicity of IL-2 in order to realize its full potential for patients, several novel engineering strategies are being developed and IL-2 based immunotherapy for cancer has emerged as a burgeoning field of clinical and experimental research. In addition, combination of IL-2 with PD-1/L1 pathway blockade shows vastly improved anti-tumor efficacy over either monotherapy in preclinical tumor models. In this review we discuss the biological characteristics of IL-2 and its receptors, as well as its efficacy and treatment limiting toxicities in cancer patients. We also explore the efforts aimed at developing novel and safer IL-2 therapies to harness the full therapeutic potential of this cytokine.

Elevated levels of IL-12/IL-23p40 in Nova Scotia Duck Tolling Retrievers with autoimmune disease and lymphoma

The Nova Scotia Duck Tolling Retriever (NSDTR) is predisposed to immune mediated rheumatic disease (IMRD), steroid-responsive meningitis-arteritis (SRMA) and certain forms of cancer. Cytokines are the main regulators of the immune system. Interleukin 2 is a cytokine involved in activation of T regulatory cells, playing a role in central tolerance and tumor immunity. Interleukin 12 and interleukin 23 share the same subunit, p40, and are both pro-inflammatory cytokines. The aim of this study was to compare levels of IL-2 in healthy NSDTRs to those with cancer or autoimmune disease and to compare levels of IL-12/IL-23p40 in healthy NSDTRs and beagles versus NSDTRs with cancer or autoimmune disease. 62 dogs were included in the analysis of IL-12/IL-23p40; healthy NSDTRs (n = 16), healthy beagles (n = 16), NSDTRs autoimmune (n = 18) and NDSTRs lymphoma/mastocytoma (n = 12) and 68 dogs for IL-2; healthy (n = 20), autoimmune (n = 36) and lymphoma/mastocytoma/adenocarcinoma (n = 12). NSDTRs with autoimmune disease had higher levels of IL-12/IL-23p40 compared to healthy dogs (p = 0.008). NSDTRs with lymphoma also had higher levels of IL-12/IL-23p40 compared to healthy NSDTRs (p = 0.002). There was no difference in levels of IL-2 between healthy and diseased NSDTR. Statistical analysis was performed using Bonferroni corrections for multiple testing. These findings can contribute to the knowledge of autoimmune disease and cancer in dogs.

Novel therapeutic strategies targeting abnormal T-cell signaling in systemic lupus erythematosus

Therapeutic strategies for autoimmune diseases have been based on the use of glucocorticoids and immunosuppressive agents that broadly suppress immune responses. Therefore, organ damage from long-term use and infections due to immunocompromised status have been significant issues. Safer immunosuppressants and biological agents are now available, but there is still an urgent need to develop specific drugs to replace glucocorticoids. T-lymphocytes, central players in immune responses, could be crucial targets in the treatment of autoimmune diseases. Extensive research has been conducted on the phenotypic changes of T-cells in systemic lupus erythematosus, which has led to the discovery of various therapeutic strategies. In this comprehensive review, we discuss novel treatment approaches and target molecules with expected effectiveness in humans and mice, based on research for lymphocytes involved in autoimmune diseases, especially T-cells in SLE.

Epithelial IL-2 is critical for NK cell-mediated cancer immunosurveillance in mammary glands

Interleukin 2 (IL-2) is the first identified cytokine and its interaction with receptors has been known to shape the immune responses in many lymphoid or non-lymphoid tissues for more than four decades. Active T cells are the primary cellular source for IL-2 production and epithelial cells have never been considered the major cellular source of IL-2 under physiological conditions. It is, however, tempting to speculate that epithelial cells could potentially express IL-2 that regulates the intricate interactions between epithelial cells and lymphocytes. Datamining our recently published single-cell RNAseq in the mouse mammary gland identified IL-2 expression in mammary epithelial cells, which is induced by prolactin via the STAT5 signaling pathway. Furthermore, epithelial IL-2 plays a crucial role in maintaining the physiological functions of natural killer (NK) cells within the mammary glands. IL-2 deletion in the mammary epithelial cells leads to a significant reduction in the number and function of NK cells, which in turn results in defective immunosurveillance, expansion of luminal epithelial cells, and tumor development. Interestingly, T cells in the mammary glands are not changed, indicating the specific regulation of NK cells by epithelial IL-2 production. In agreement, we also found that human epithelial cells express IL-2 and NK cells express the highest level of IL2RB among all the immune cells. Here, we provide the first evidence that epithelial cells produce IL-2, which is critical for maintaining the physiological functions of NK cells in immunosurveillance.

The efficacy and safety of short-term and low-dose IL-2 combined with tocilizumab to treat rheumatoid arthritis

Background

Immunotherapy targeting factors related to immune imbalance has been widely employed for RA treatment. This study aimed to evaluate the efficacy and safety of low-dose interleukin (IL)-2 combined with tocilizumab (TCZ), a biologics targeting IL-6, in RA patients.

Methods

Fifty adults with active RA who met the criteria with complete clinical data were recruited, and divided into three groups: control group (n=15), IL-2 group (n=26), and IL-2+TCZ group (n=9). In addition to basic treatment, participants in the IL-2 group received IL-2 (0.5 MIU/day), while participants in the IL-2+TCZ group received IL-2 (0.5 MIU/day) along with one dose of TCZ (8 mg/kg, maximum dose: 800 mg). All subjects underwent condition assessment, laboratory indicators and safety indicators detection, and records before treatment and one week after treatment.

Results

Compared with the baseline, all three groups showed significant improvement in disease conditions, as evidenced by significantly reduced disease activity indicators. The low-dose IL-2 and combination treatment groups demonstrated a violent proliferation of Tregs, while the absolute number of Th1, Th2, and Th17 cells in the latter group showed a decreasing trend. The decrease in the Th17/Treg ratio was more pronounced in the IL-2+TCZ groups. No significant adverse reactions were observed in any of the patients.

Conclusion

Exogenous low doses of IL-2 combined TCZ were found to be safe and effective in reducing effector T cells and appropriately increasing Treg levels in RA patients with high effector T cell levels. This approach helps regulate immune homeostasis and contributes to the prevention of disease deterioration.

Clinical trial registration

https://www.chictr.org.cn/showprojEN.html?proj=13909, identifier ChiCTR-INR-16009546.

Fine tuning of the innate and adaptive immune responses by Interleukin-2

Novel immunotherapies for cancer and other diseases aim to trigger the immune system to produce durable responses, while overcoming the immunosuppression that may contribute to disease severity, and in parallel considering immunosafety aspects. Interleukin-2 (IL-2) was one of the first cytokines that the FDA approved as a cancer-targeting immunotherapy. However, in the past years, IL-2 immunotherapy is not actively offered to patients, due to limited efficacy, when compared to other novel immunotherapies, and the associated severe adverse events. In order to design improved in vitro and in vivo models, able to predict the efficacy and safety of novel IL-2 alternatives, it is important to delineate the mechanistic immunological events triggered by IL-2. Particularly, in this review we will discuss the effects IL-2 has with the bridging cell type of the innate and adaptive immune responses, dendritic cells. The pathways involved in the regulation of IL-2 by dendritic cells and T-cells in cancer and autoimmune disease will also be explored.

Interleukin-2 signaling in the regulation of T cell biology in autoimmunity and cancer

Interleukin-2 (IL-2) is a critical cytokine for T cell peripheral tolerance and immunity. Here, we review how IL-2 interaction with the high-affinity IL-2 receptor (IL-2R) supports the development and homeostasis of regulatory T cells and contributes to the differentiation of helper, cytotoxic, and memory T cells. A critical element for each T cell population is the expression of CD25 (Il2rα), which heightens the receptor affinity for IL-2. Signaling through the high-affinity IL-2R also reinvigorates CD8+ exhausted T (Tex) cells in response to checkpoint blockade. We consider the molecular underpinnings reflecting how IL-2R signaling impacts these various T cell subsets and the implications for enhancing IL-2-dependent immunotherapy of autoimmunity, other inflammatory disorders, and cancer.

Molecular Engineering of Interleukin-2 for Enhanced Therapeutic Activity in Autoimmune Diseases

The interleukin-2 (IL-2) cytokine plays a crucial role in regulating immune responses and maintaining immune homeostasis. Its immunosuppressive effects have been harnessed therapeutically via administration of low cytokine doses. Low-dose IL-2 has shown promise in the treatment of various autoimmune and inflammatory diseases; however, the clinical use of IL-2 is complicated by its toxicity, its pleiotropic effects on both immunostimulatory and immunosuppressive cell subsets, and its short serum half-life, which collectively limit the therapeutic window. As a result, there remains a considerable need for IL-2-based autoimmune disease therapies that can selectively target regulatory T cells with minimal off-target binding to immune effector cells in order to prevent cytokine-mediated toxicities and optimize therapeutic efficacy. In this review, we discuss exciting advances in IL-2 engineering that are empowering the development of novel therapies to treat autoimmune conditions. We describe the structural mechanisms of IL-2 signaling, explore current applications of IL-2-based compounds as immunoregulatory interventions, and detail the progress and challenges associated with clinical adoption of IL-2 therapies. In particular, we focus on protein engineering approaches that have been employed to optimize the regulatory T-cell bias of IL-2, including structure-guided or computational design of cytokine mutants, conjugation to polyethylene glycol, and the development of IL-2 fusion proteins. We also consider future research directions for enhancing the translational potential of engineered IL-2-based therapies. Overall, this review highlights the immense potential to leverage the immunoregulatory properties of IL-2 for targeted treatment of autoimmune and inflammatory diseases.

The soluble IL-2 receptor α/CD25 as a modulator of IL-2 function

The pleiotropic cytokine interleukin-2 (IL-2) is an integral regulator of healthy and pathological immune responses, with the most important role in regulating the homeostasis of regulatory T cells. IL-2 signalling involves three distinct receptors: The IL-2 receptor α (IL-2Rα/CD25), IL-2Rβ, and IL-2Rγ/γc . While IL-2Rβ and γc are essential for signal transduction, IL-2Rα regulates the affinity of the receptor complex towards IL-2. A soluble form of the IL-2Rα (sIL-2Rα) is present in the blood of healthy individuals and increased under various pathological conditions. Although it is known that the sIL-2Rα retains its ability to bind IL-2, it is not fully understood how this molecule affects IL-2 function and thus immune responses. Here, we summarize the current knowledge on the generation and function of the sIL-2Rα. We describe the molecular mechanisms leading to sIL-2Rα generation and discuss the different IL-2 modulating functions that have been attributed to the sIL-2Rα. Finally, we describe attempts to utilize the sIL-2Rα as a therapeutic tool.

"IL-2 immunotherapy for targeting regulatory T cells in autoimmunity"

FOXP3+ regulatory T cells (Treg) are indispensable for immune homoeostasis and for the prevention of autoimmune diseases. Interleukin-2 (IL-2) signalling is critical in all aspects of Treg biology. Consequences of defective IL-2 signalling are insufficient numbers or dysfunction of Treg and hence autoimmune disorders in human and mouse. The restoration and maintenance of immune homoeostasis remain central therapeutic aims in the field of autoimmunity. Historically, broadly immunosuppressive drugs with serious side-effects have been used for the treatment of autoimmune diseases or prevention of organ-transplant rejection. More recently, ex vivo expanded or in vivo stimulated Treg have been shown to induce effective tolerance in clinical trials supporting the clinical benefit of targeting natural immunosuppressive mechanisms. Given the central role of exogenous IL-2 in Treg homoeostasis, a new and promising focus in drug development are IL-2-based approaches for in vivo targeted expansion of Treg or for enhancement of their suppressive activity. In this review, we summarise the role of IL-2 in Treg biology and consequences of dysfunctional IL-2 signalling pathways. We then examine evidence of efficacy of IL-2-based biological drugs targeting Treg with specific focus on therapeutic candidates in clinical trials and discuss their limitations.

Unveiling the hidden players: The crucial role of transposable elements in the placenta and their potential contribution to pre-eclampsia

The human placenta is a vital connection between maternal and fetal tissues, allowing for the exchange of molecules and modulation of immune interactions during pregnancy. Interestingly, some of the placenta's unique functions can be attributed to transposable elements (TEs), which are DNA sequences that have mobilised into the genome. Co-option throughout mammalian evolution has led to the generation of TE-derived regulators and TE-derived genes, some of which are expressed in the placenta but silenced in somatic tissues. TE genes encompass both TE-derived genes with a repeat element in the coding region and TE-derived regulatory regions such as alternative promoters and enhancers. Placental-specific TE genes are known to contribute to the placenta's unique functions, and interestingly, they are also expressed in some cancers and share similar functions. There is evidence to support that aberrant activity of TE genes may contribute to placental pathologies, cancer and autoimmunity. In this review, we highlight the crucial roles of TE genes in placental function, and how their dysregulation may lead to pre-eclampsia, a common and dangerous placental condition. We provide a summary of the functional TE genes in the placenta to offer insight into their significance in normal and abnormal human development. Ultimately, this review highlights an opportunity for future research to investigate the potential dysregulation of TE genes in the development of placental pathologies such as pre-eclampsia. Further understanding of TE genes and their role in the placenta could lead to significant improvements in maternal and fetal health.

Low-dose interleukin-2 therapy in systemic lupus erythematosus

In systemic lupus erythematosus (SLE), T regulatory cells (Tregs) contribute to the inhibition of autoimmune responses by suppressing self-reactive immune cells. Interleukin (IL)-2 plays an essential role in the generation, function and homeostasis of the Tregs and is reduced in SLE. Several clinical studies, including randomized trials, have shown that low-dose IL-2 therapy in SLE patients is safe and effective and can reduce disease manifestations. This review discusses the rationale for the use of low-dose IL-2 therapy in SLE, the clinical responses in patients, and the effects of this therapy on different types of T cells. Considerations are made on the current and future directions of use of low-dose IL-2 regimens in SLE.

Low-dose IL-2 enhances the generation of IL-10-producing immunoregulatory B cells

Dysfunction of interleukin-10 producing regulatory B cells has been associated with the pathogenesis of autoimmune diseases, but whether regulatory B cells can be therapeutically induced in humans is currently unknown. Here we demonstrate that a subset of activated B cells expresses CD25, and the addition of low-dose recombinant IL-2 to in vitro stimulated peripheral blood and splenic human B cells augments IL-10 secretion. Administration of low dose IL-2, aldesleukin, to patients increases IL-10-producing B cells. Single-cell RNA sequencing of circulating immune cells isolated from low dose IL2-treated patients reveals an increase in plasmablast and plasma cell populations that are enriched for a regulatory B cell gene signature. The transcriptional repressor BACH2 is significantly down-regulated in plasma cells from IL-2-treated patients, BACH2 binds to the IL-10 gene promoter, and Bach2 depletion or genetic deficiency increases B cell IL-10, implicating BACH2 suppression as an important mechanism by which IL-2 may promote an immunoregulatory phenotype in B cells.

IL-2-based approaches to Treg enhancement

Immune homeostasis is heavily dependent on the action of regulatory T cells (Tregs) which act to suppress the activation of many immune cell types including autoreactive conventional T cells. A body of evidence has shown that Tregs are intrinsically defective in many common autoimmune diseases, and gene polymorphisms which increase the susceptibility of autoimmune disease development have implicated the interleukin-2 (IL-2) signaling pathway as a key dysregulated mechanism. IL-2 is essential for Treg function and survival, and Tregs are highly sensitive to low levels of this cytokine in their environment. This review will revisit the rationale behind using low-dose IL-2 as a therapy to treat autoimmune diseases and evaluate the outcomes of trials to date. Furthermore, novel engineered IL-2 therapies with increased Treg specificity have shown promise in pre-clinical studies and human clinical trials for some agents have begun. Future studies will determine whether low-dose IL-2 or engineered IL-2 therapies can change the course of autoimmune and inflammatory diseases in patients.

Principles of regulatory T cell function

Regulatory T (Treg) cells represent a distinct lineage of cells of the adaptive immune system indispensable for forestalling fatal autoimmune and inflammatory pathologies. The role of Treg cells as principal guardians of the immune system can be attributed to their ability to restrain all currently recognized major types of inflammatory responses through modulating the activity of a wide range of cells of the innate and adaptive immune system. This broad purview over immunity and inflammation is afforded by the multiple modes of action Treg cells exert upon their diverse molecular and cellular targets. Beyond the suppression of autoimmunity for which they were originally recognized, Treg cells have been implicated in tissue maintenance, repair, and regeneration under physiologic and pathologic conditions. Herein, we discuss the current and emerging understanding of Treg cell effector mechanisms in the context of the basic properties of Treg cells that endow them with such functional versatility.

Research advances on targeted-Treg therapies on immune-mediated kidney diseases

The primary function of regulatory T cells (Tregs) is blocking the pathogenic immunological response mediated by autoreactive cells, establishing and maintaining immune homeostasis in tissues. Kidney diseases are often caused by Immune imbalance, including alloimmune graft damage after renal transplantation, direct immune-mediated kidney diseases like membranous nephropathy (MN) and anti-glomerular basement membrane (anti-GBM) glomerulonephritis, as well as indirect immune-mediated ones like Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAVs), IgA nephropathy (IgAN) and lupus nephritis (LN). Treg cells are deficient numerically and/or functionally in those kidney diseases. Targeted-Treg therapies, including adoptive Tregs transfer therapy and low-dose IL-2 therapy, have begun to thrive in treating autoimmune diseases in recent years. However, the clinical use of targeted Treg-therapies is rarely mentioned in those kidney diseases above except for kidney transplantation. This article mainly discusses the newest progressions of targeted-Treg therapies in those specific examples of immune-mediated kidney diseases. Meanwhile, we also reviewed the main factors that affect Treg development and differentiation, hoping to inspire new strategies to develop target Tregs-therapies. Lastly, we emphasize the significant impediments and prospects to the clinical translation of target-Treg therapy. We advocate for more preclinical and clinical studies on target Tregs-therapies to decipher Tregs in those diseases.

Soluble CD25 imposes a low-zone IL-2 signaling environment that favors competitive outgrowth of antigen-experienced CD25high regulatory and memory T cells

This study focused on soluble (s)CD25-mediated regulation of IL-2 signaling in murine and human CD4+ T cells. Recombinant sCD25 reversibly sequestered IL-2 to limit acute maximal proliferative responses while preserving IL-2 bioavailability to subsequently maintain low-zone IL-2 signaling during prolonged culture. By inhibiting IL-2 signaling during acute activation, sCD25 suppressed T-cell growth and inhibited IL-2-evoked transmembrane CD25 expression, thereby resulting in lower prevalence of CD25high T cells. By inhibiting IL-2 signaling during quiescent IL-2-mediated growth, sCD25 competed with transmembrane CD25, IL2Rβγ, and IL2Rαβγ receptors for limited pools of IL-2 such that sCD25 exhibited strong or weak inhibitory efficacy in IL-2-stimulated cultures of CD25low or CD25high T cells, respectively. Preferential blocking of IL-2 signaling in CD25low but not CD25high T cells caused competitive enrichment of CD25high memory/effector and regulatory FOXP3+ subsets. In conclusion, sCD25 modulates IL-2 bioavailability to limit CD25 expression during acute activation while enhancing CD25highT-cell dominance during low-zone homeostatic IL-2-mediated expansion, thereby 'flattening' the inflammatory curve over time.

STAT5b: A master regulator of key biological pathways

The Signal Transducer and Activator of Transcription (STAT)-5 proteins are required in immune regulation and homeostasis and play a crucial role in the development and function of several hematopoietic cells. STAT5b activation is involved in the expression of genes that participate in cell development, proliferation, and survival. STAT5a and STAT5b are paralogs and only human mutations in STAT5B have been identified leading to immune dysregulation and hematopoietic malignant transformation. The inactivating STAT5B mutations cause impaired post-natal growth, recurrent infections and immune dysregulation, whereas gain of function somatic mutations cause dysregulated allergic inflammation. These mutations are rare, and they are associated with a wide spectrum of clinical manifestations which provide a disease model elucidating the biological mechanism of STAT5 by studying the consequences of perturbations in STAT5 activity. Further, the use of Jak inhibitors as therapy for a variety of autoimmune and malignant disorders has increased substantially heading relevant lessons for the consequences of Jak/STAT immunomodulation from the human model. This review summarizes the biology of the STAT5 proteins, human disease associate with molecular defects in STAT5b, and the connection between aberrant activation of STAT5b and the development of certain cancers.

IL2RB affects Th1/Th2 and Th17 responses of peripheral blood mononuclear cells from septic patients

BACKGROUND

Immune dysfunction is a common and serious complication of sepsis. This study finds key genes linked to immunity in sepsis.

METHODS

The "Limma package" was used to analyze GSE154918 datasets for differentially expressed genes. The differentially expressed genes were then enriched for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and interleukin 2 receptor subunit Beta (IL2RB) protein coding gene was chosen for investigation. IL2RB expression in peripheral blood mononuclear cells (PBMC) was assessed by polymerase chain reaction. White blood cells of septic patients and healthy controls were collected from hospitals and linked with acute physiology and chronic health evaluation (APACHE) II, sequential organ failure assessment (SOFA), C-reactive protein (CRP), and procalcitonin (PCT) of septic patients using Pearson's correlation analysis. PBMC cells were transfected with IL2RB, and the effect of transfection was observed on cellular interferon gamma (IFN-γ), interleukin (IL)-12, IL-4, IL-10, and IL-17A.

RESULTS

A total of 686 differential genes, comprising 446 upregulated and 240 down regulated genes, were identified. The enrichment of KEGG pathway revealed that the majority of differential genes were enriched in the T helper (Th1)/Th2 cell and Th17 cell differentiation pathways. In patients with sepsis, correlation analysis revealed a negative correlation between IL2RB and APACHE II score, SOFA score, CRP, and PCT. IFN-γ and IL-12 levels were elevated in PBMC of septic patients after IL2RB transfection, but IL-4, IL-10, and IL-17A levels were lowered.

CONCLUSION

Sepsis-induced immunological dysfunction is improved by IL2RB, which also balances Th1/Th2 responses and prevents Th17 activation. © 2023 Codon Publications. Published by Codon Publications.

Emerging principles of cytokine pharmacology and therapeutics

Cytokines are secreted signalling proteins that play essential roles in the initiation, maintenance and resolution of immune responses. Although the unique ability of cytokines to control immune function has garnered clinical interest in the context of cancer, autoimmunity and infectious disease, the use of cytokine-based therapeutics has been limited. This is due, in part, to the ability of cytokines to act on many cell types and impact diverse biological functions, resulting in dose-limiting toxicity or lack of efficacy. Recent studies combining structural biology, protein engineering and receptor pharmacology have unlocked new insights into the mechanisms of cytokine receptor activation, demonstrating that many aspects of cytokine function are highly tunable. Here, we discuss the pharmacological principles underlying these efforts to overcome cytokine pleiotropy and enhance the therapeutic potential of this important class of signalling molecules.

Microbial polysaccharides: An emerging family of natural biomaterials for cancer therapy and diagnostics

Microbial polysaccharides (MPs) offer immense diversity in structural and functional properties. They are extensively used in advance biomedical science owing to their superior biodegradability, hemocompatibility, and capability to imitate the natural extracellular matrix microenvironment. Ease in tailoring, inherent bio-activity, distinct mucoadhesiveness, ability to absorb hydrophobic drugs, and plentiful availability of MPs make them prolific green biomaterials to overcome the significant constraints of cancer chemotherapeutics. Many studies have demonstrated their application to obstruct tumor development and extend survival through immune activation, apoptosis induction, and cell cycle arrest by MPs. Synoptic investigations of MPs are compulsory to decode applied basics in recent inclinations towards cancer regimens. The current review focuses on the anticancer properties of commercially available and newly explored MPs, and outlines their direct and indirect mode of action. The review also highlights cutting-edge MPs-based drug delivery systems to augment the specificity and efficiency of available chemotherapeutics, as well as their emerging role in theranostics.

Engineering IL-2 for immunotherapy of autoimmunity and cancer

Preclinical studies of the T cell growth factor activity of IL-2 resulted in this cytokine becoming the first immunotherapy to be approved nearly 30 years ago by the US Food and Drug Administration for the treatment of cancer. Since then, we have learnt the important role of IL-2 in regulating tolerance through regulatory T cells (Treg cells) besides promoting immunity through its action on effector T cells and memory T cells. Another pivotal event in the history of IL-2 research was solving the crystal structure of IL-2 bound to its tripartite receptor, which spurred the development of cell type-selective engineered IL-2 products. These new IL-2 analogues target Treg cells to counteract the dysregulated immune system in the context of autoimmunity and inflammatory disorders or target effector T cells, memory T cells and natural killer cells to enhance their antitumour responses. IL-2 biologics have proven to be effective in preclinical studies and clinical assessment of some is now underway. These studies will soon reveal whether engineered IL-2 biologics are truly capable of harnessing the IL-2-IL-2 receptor pathway as effective monotherapies or combination therapies for autoimmunity and cancer.

Dendritic cell-derived IL-27 p28 regulates T cell program in pathogenicity and alleviates acute graft-versus-host disease

Interleukin 27 (IL-27), a heterodimeric cytokine composed of Epstein-Barr virus-induced 3 and p28, is a pleiotropic cytokine with both pro-and anti-inflammatory properties. However, the precise role of IL-27 in acute graft-versus-host disease is not yet fully understood. In this study, utilizing mice with IL-27 p28 deficiency in dendritic cells (DCs), we demonstrated that IL-27 p28 deficiency resulted in impaired Treg cell function and enhanced effector T cell responses, corresponding to aggravated aGVHD in mice. In addition, using single-cell RNA sequencing, we found that loss of IL-27 p28 impaired Treg cell generation and promoted IL-1R2⁺TIGIT⁺ pathogenic CD4⁺ T cells in the thymus at a steady state. Mechanistically, IL-27 p28 deficiency promoted STAT1 phosphorylation and Th1 cell responses, leading to the inhibition of Treg cell differentiation and function. Finally, patients with high levels of IL-27 p28 in serum showed a substantially decreased occurrence of grade II-IV aGVHD and more favorable overall survival than those with low levels of IL-27 p28. Thus, our results suggest a protective role of DC-derived IL-27 p28 in the pathogenesis of aGVHD through modulation of the Treg/Teff cell balance during thymic development. IL-27 p28 may be a valuable marker for predicting aGVHD development after transplantation in humans.

IL-2 and IL-15 drive intrathymic development of distinct periphery-seeding CD4+Foxp3+ regulatory T lymphocytes

Development of Foxp3-expressing regulatory T-lymphocytes (Treg) in the thymus is controlled by signals delivered in T-cell precursors via the TCR, co-stimulatory receptors, and cytokine receptors. In absence of IL-2, IL-15 or their receptors, fewer Treg apparently develop in the thymus. However, it was recently shown that a substantial part of thymic Treg are cells that had recirculated from the periphery back to the thymus, troubling interpretation of these results. We therefore reassessed the involvement of IL-2 and IL-15 in the development of Treg, taking into account Treg-recirculation. At the age of three weeks, when in wt and IL-15-deficient (but not in IL-2-deficient) mice substantial amounts of recirculating Treg are present in the thymus, we found similarly reduced proportions of newly developed Treg in absence of IL-2 or IL-15, and in absence of both cytokines even less Treg developed. In neonates, when practically no recirculating Treg were found in the thymus, the absence of IL-2 led to substantially more reduced Treg-development than deficiency in IL-15. IL-2 but not IL-15 modulated the CD25, GITR, OX40, and CD73-phenotypes of the thymus-egress-competent and periphery-seeding Treg-population. Interestingly, IL-2 and IL-15 also modulated the TCR-repertoire expressed by developing Treg. Upon transfer into Treg-less Foxp3^sf mice, newly developed Treg from IL-2- (and to a much lesser extent IL-15-) deficient mice suppressed immunopathology less efficiently than wt Treg. Taken together, our results firmly establish important non-redundant quantitative and qualitative roles for IL-2 and, to a lesser extent, IL-15 in intrathymic Treg-development.

Polygenic autoimmune disease risk alleles impacting B cell tolerance act in concert across shared molecular networks in mouse and in humans

Most B cells produced in the bone marrow have some level of autoreactivity. Despite efforts of central tolerance to eliminate these cells, many escape to periphery, where in healthy individuals, they are rendered functionally non-responsive to restimulation through their antigen receptor via a process termed anergy. Broad repertoire autoreactivity may reflect the chances of generating autoreactivity by stochastic use of germline immunoglobulin gene segments or active mechanisms may select autoreactive cells during egress to the naïve peripheral B cell pool. Likewise, it is unclear why in some individuals autoreactive B cell clones become activated and drive pathophysiologic changes in autoimmune diseases. Both of these remain central questions in the study of the immune system(s). In most individuals, autoimmune diseases arise from complex interplay of genetic risk factors and environmental influences. Advances in genome sequencing and increased statistical power from large autoimmune disease cohorts has led to identification of more than 200 autoimmune disease risk loci. It has been observed that autoantibodies are detectable in the serum years to decades prior to the diagnosis of autoimmune disease. Thus, current models hold that genetic defects in the pathways that control autoreactive B cell tolerance set genetic liability thresholds across multiple autoimmune diseases. Despite the fact these seminal concepts were developed in animal (especially murine) models of autoimmune disease, some perceive a disconnect between human risk alleles and those identified in murine models of autoimmune disease. Here, we synthesize the current state of the art in our understanding of human risk alleles in two prototypical autoimmune diseases - systemic lupus erythematosus (SLE) and type 1 diabetes (T1D) along with spontaneous murine disease models. We compare these risk networks to those reported in murine models of these diseases, focusing on pathways relevant to anergy and central tolerance. We highlight some differences between murine and human environmental and genetic factors that may impact autoimmune disease development and expression and may, in turn, explain some of this discrepancy. Finally, we show that there is substantial overlap between the molecular networks that define these disease states across species. Our synthesis and analysis of the current state of the field are consistent with the idea that the same molecular networks are perturbed in murine and human autoimmune disease. Based on these analyses, we anticipate that murine autoimmune disease models will continue to yield novel insights into how best to diagnose, prognose, prevent and treat human autoimmune diseases.

Immunoregulation via Cell Density and Quorum Sensing-like Mechanisms: An Underexplored Emerging Field with Potential Translational Implications

Quorum sensing (QS) was historically described as a mechanism by which bacteria detect and optimize their population density via gene regulation based on dynamic environmental cues. Recently, it was proposed that QS or similar mechanisms may have broader applications across different species and cell types. Indeed, emerging evidence shows that the mammalian immune system can also elicit coordinated responses on a population level to regulate cell density and function, thus suggesting that QS-like mechanisms may also be a beneficial trait of the immune system. In this review, we explore and discuss potential QS-like mechanisms deployed by the immune system to coordinate cellular-level responses, such as T cell responses mediated via the common gamma chain (γc) receptor cytokines and the aryl hydrocarbon receptors (AhRs). We present evidence regarding a novel role of QS as a multifunctional mechanism coordinating CD4⁺ and CD8⁺ T cell behavior during steady state and in response to infection, inflammatory diseases, and cancer. Successful clinical therapies such as adoptive cell transfer for cancer treatment may be re-evaluated to harness the effects of the QS mechanism(s) and enhance treatment responsiveness. Moreover, we discuss how signaling threshold perturbations through QS-like mediators may result in disturbances of the complex crosstalk between immune cell populations, undesired T cell responses, and induction of autoimmune pathology. Finally, we discuss the potential therapeutic role of modulating immune-system-related QS as a promising avenue to treat human diseases.

Upregulated Expression of IL2RB Causes Disorder of Immune Microenvironment in Patients with Kawasaki Disease

Aims. The clinical diagnosis of Kawasaki disease (KD) is not easy because of many atypical manifestations. This study is aimed at finding potential diagnostic markers and therapeutic targets for KD and analysing their correlation with immune cell infiltrations. Methods. First, we downloaded the KD dataset from the Gene Expression Omnibus (GEO) database and used R software to identify differentially expressed genes (DEGs) and perform functional correlation analysis. Then, CIBERSORT algorithm was used to evaluate immune cell infiltrations in samples. Coexpression analysis between DEGs and infiltrating immune cells was performed to screen the main infiltrating immune cells. Subsequently, the least absolute shrinkage and selection operator (LASSO) logistic regression analysis was used to screen the core genes related to KD. Finally, correlation analysis between the core genes and the main infiltrating immune cells was performed. Results. 327 DEGs were screened out in this study. Among them, 72 shared genes were the category of genes most likely to be disease-causing for they did not change before and after treatment. After analysis, it was found that expression level of IL2RB in KD tissues was significantly upregulated, the number of resting CD4+ memory T cells was decreased, and the decrease was significantly negatively correlated with the upregulated expression of IL2RB. Therefore, it was speculated that the upregulated expression of IL2RB disrupted Th1/Th2 cell differentiation balance, which led to a decrease of resting CD4+ memory T cells and finally caused disorder of immune microenvironment in patients with KD. Conclusions. Upregulated expression of IL2RB leads to disorder of immune microenvironment in patients with KD and eventually causes the occurrence and development of KD. Therefore, IL2RB may serve as a diagnostic marker and potential therapeutic target for KD.

Abnormalities of T cells in systemic lupus erythematosus: new insights in pathogenesis and therapeutic strategies

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by loss of immune tolerance and sustained production of autoantibodies. Multiple and profound T cell abnormalities in SLE are intertwined with disease expression. Both numerical and functional disturbances have been reported in main CD4⁺ T helper cell subsets including Th1, Th2, Th17, regulatory, and follicular helper cells. SLE CD4⁺ T cells are known to provide help to B cells, produce excessive IL-17 but insufficient IL-2, and infiltrate tissues. In the absence of sufficient amounts of IL-2, regulatory T cells, do not function properly to constrain inflammation. A complicated series of early signaling defects and aberrant activation of kinases and phosphatases result in complex cell phenotypes by altering the metabolic profile and the epigenetic landscape. All main metabolic pathways including glycolysis, glutaminolysis and oxidative phosphorylation are altered in T cells from lupus prone mice and patients with SLE. SLE CD8⁺ cytotoxic T cells display reduced cytolytic activity which accounts for higher rates of infection and the sustenance of autoimmunity. Further, CD8⁺ T cells in the context of rheumatic diseases lose the expression of CD8, acquire IL-17⁺CD4^-CD8^- double negative T (DNT) cell phenotype and infiltrate tissues. Herein we present an update on these T cell abnormalities along with underlying mechanisms and discuss how these advances can be exploited therapeutically. Novel strategies to correct these aberrations in T cells show promise for SLE treatment.

Competitive inhibition of IL-2/IL-2R has a dual effect on HSC ex vivo expansion and IL-2R (CD25) content

Interleukin-2 (IL-2) and its receptor play a pivotal role in the regulation of immune response and possess both immune-regulatory and immune-stimulatory functions. As a cytokine of lymphoid cells, the role of IL-2 has been revealed in hematopoietic stem cell (HSC) maintenance and proper hematopoiesis. Here, we investigated that small molecule Ro 26-4550 trifluoroacetate (Ro) mediated competitive inhibition of IL-2 and its receptor alpha subunit (IL-2Rα) throughout ex vivo culture. Ro treatment induced murine and human ex vivo expansion of hematopoietic stem and progenitor cells (HSPCs). Ro treated HSPCs sustained self-renewal ability and low apoptotic activity. As a competitive inhibitor of IL-2/IL-2Rα interaction, Ro small molecule induced human HSPCs to entry into cell cycle. The proliferation of bone marrow mesenchymal stem cells (MSC) and fibroblasts were also highly increased post treatment. Besides, Ro treatment enhanced IL-2Rα (CD25) expression independent of IL-2 administration in human mPB-derived HSPCs and BM-derived HSPCs. Increased IL-2Rα (CD25) expression in BM-HSPCs was associated with the increase in the CD4⁺CD25⁺ T cell population. Xenotransplantation of immunodeficient mice with ex vivo expanded human CD34⁺ cells after Ro treatment revealed an efficient multi-lineage reconstitution in the recipient. These findings shed light on the role of IL-2/IL-2Rα interaction in HSC expansion, in vivo and in vitro HSC self-renewal ability and repopulation capacity as well as a possible mean for the induction of CD25 expressing cells in hematopoietic compartments.

Selective activation and expansion of regulatory T cells using lipid encapsulated mRNA encoding a long-acting IL-2 mutein

Interleukin-2 (IL-2) is critical for regulatory T cell (Treg) function and homeostasis. At low doses, IL-2 can suppress immune pathologies by expanding Tregs that constitutively express the high affinity IL-2Rα subunit. However, even low dose IL-2, signaling through the IL2-Rβ/γ complex, may lead to the activation of proinflammatory, non-Treg T cells, so improving specificity toward Tregs may be desirable. Here we use messenger RNAs (mRNA) to encode a half-life-extended human IL-2 mutein (HSA-IL2m) with mutations promoting reliance on IL-2Rα. Our data show that IL-2 mutein subcutaneous delivery as lipid-encapsulated mRNA nanoparticles selectively activates and expands Tregs in mice and non-human primates, and also reduces disease severity in mouse models of acute graft versus host disease and experimental autoimmune encephalomyelitis. Single cell RNA-sequencing of mouse splenic CD4+ T cells identifies multiple Treg states with distinct response dynamics following IL-2 mutein treatment. Our results thus demonstrate the potential of mRNA-encoded HSA-IL2m immunotherapy to treat autoimmune diseases.

New therapeutic strategies based on biasing IL-2 mutants for cancers and autoimmune diseases

Interleukin-2 (IL-2) is an immunomodulatory multifunctional cytokine. High-dose IL-2 was first approved by the U.S. Food and Drug Administration (FDA) in the 1990s for the treatment of metastatic renal cell carcinoma and metastatic melanoma. However, the short half-life of IL-2 and its toxicity caused by high-dose IL-2 limit the clinical use of IL-2. Recently, the development of cell-type-selective engineered IL-2 products become a hot research filed, mainly because IL-2 stimulates both regulatory T cells (Treg) and effector T cells (Teff) in vivo. The selective effect of IL-2 on Treg and Teff can be improved by designing biased IL-2 mutants, which showed reduced toxicity while being more effective in stimulating anti-tumor effector immunity or ameliorating autoimmune diseases. In this review we summarize the biological properties of IL-2 mutants reported so far. The design process and principle of IL-2 mutants, IL-2 mutant antibody complexes and IL-2 fusion proteins were discussed, which provided research basis for the design and application of IL-2 mutants in the future.

Role of Cytokines in Thymic Regulatory T Cell Generation: Overview and Updates

CD4⁺CD25⁺Foxp3⁺ Regulatory (Treg) T cells are mainly generated within the thymus. However, the mechanism of thymic Treg cell (tTreg cell) generation remains to be fully revealed. Although the functions of TCR/CD28 co-stimulation have been widely accepted, the functions of cytokines in the generation of tTreg cells remain highly controversial. In this review, we summarize the existing studies on cytokine regulation of tTreg cell generation. By integrating the key findings of cytokines in tTreg cell generation, we have concluded that four members of γc family cytokines (IL-2, IL-4, IL-7 and IL-15), transforming growth factor β (TGF-β), and three members of TNF superfamily cytokines (GITRL, OX40L and TNF-α) play vitally important roles in regulating tTreg cell generation. We also point out all disputed points and highlight critical scientific questions that need to be addressed in the future.

Autocrine and paracrine IL-2 signals collaborate to regulate distinct phases of CD8 T cell memory

Differential interleukin-2 (IL-2) signaling and production are associated with disparate effector and memory fates. Whether the IL-2 signals perceived by CD8 T cells come from autocrine or paracrine sources, the timing of IL-2 signaling and their differential impact on CD8 T cell responses remain unclear. Using distinct models of germline and conditional IL-2 ablation in post-thymic CD8 T cells, this study shows that paracrine IL-2 is sufficient to drive optimal primary expansion, effector and memory differentiation, and metabolic function. In contrast, autocrine IL-2 is uniquely required during primary expansion to program robust secondary expansion potential in memory-fated cells. This study further shows that IL-2 production by antigen-specific CD8 T cells is largely independent of CD4 licensing of dendritic cells (DCs) in inflammatory infections with robust DC activation. These findings bear implications for immunizations and adoptive T cell immunotherapies, where effector and memory functions may be commandeered through IL-2 programming.

The link between circulating follicular helper T cells and autoimmunity

Follicular helper T (T_FH) cells provide help to B cells, supporting the formation of germinal centres that allow affinity maturation of antibody responses. Although usually located in secondary lymphoid organs, T cells bearing features of T_FH cells can also be identified in human blood, and their frequency and phenotype are often altered in people with autoimmune diseases. In this Perspective article, I discuss the increase in circulating T_FH cells seen in autoimmune settings and explore potential explanations for this phenomenon. I consider the multistep regulation of T_FH cell differentiation by the CTLA4 and IL-2 pathways as well as by regulatory T cells and highlight that these same pathways are crucial for regulating autoimmune diseases. The propensity of infection to serve as a cue for T_FH cell differentiation and a potential trigger for autoimmune disease development is also discussed. Overall, I postulate that alterations in pathways that regulate autoimmunity are coupled to alterations in T_FH cell homeostasis, suggesting that this population may serve as a core sentinel of dysregulated immunity.

The immune-enhancing effects of a mixture of Astragalus membranaceus (Fisch.) Bunge, Angelica gigas Nakai, and Trichosanthes Kirilowii (Maxim.) or its active constituent nodakenin

ETHNOPHARMACOLOGICAL RELEVANCE

A mixture (SH003) of Astragalus membranaceus (Fisch.) Bunge, Angelica gigas Nakai, and Trichosanthes Kirilowii (Maxim.) has beneficial effects against several carcinomas. There have been few reports on an immune-enhancing activity of SH003 and its active constituent nodakenin.

AIM OF THE STUDY

This study aimed at identifying the immune-enhancing effect of SH003 and nodakenin.

MATERIALS AND METHODS

The immune-enhancing effect was evaluated using RAW264.7 macrophages, mouse primary splenocytes, and a cyclophosphamide (CP)-induced immunosuppression murine model.

RESULTS

The results show that SH003 or nodakenin stimulated the production levels of granulocyte colony-stimulating factor, IL-12, IL-2, IL-6, TNF-α, and nitric oxide (NO) and the expression levels of iNOS in RAW264.7 macrophages. SH003 or nodakenin also enhanced NF-κB p65 activation in RAW264.7 macrophages. SH003 or nodakenin stimulated the production levels of IFN-γ, IL-12, IL-2, TNF-α, and NO and the expression levels of iNOS in splenocytes. SH003 or nodakenin increased the splenic lymphocyte proliferation and splenic NK cell activity. In addition, SH003 or nodakenin increased the levels of IFN-γ, IL-12, IL-2, IL-6, and TNF-α in the serum and spleen of CP-treated mice, alleviating CP-induced immunosuppression.

CONCLUSION

Taken together, the results of this study show that SH003 improved immunosuppression through the activation of macrophages, splenocytes, and NK cells. These findings suggest that SH003 could be applied as a potential immunostimulatory agent for a variety of diseases caused or exacerbated by immunodeficiency.

Contrast Enhanced Ultrasound Molecular Imaging of Spontaneous Chronic Inflammatory Bowel Disease in an Interleukin-2 Receptor α−/− Transgenic Mouse Model Using Targeted Microbubbles

Inflammatory bowel disease (IBD) is a lifelong inflammatory disorder with relapsing–remission cycles, which is currently diagnosed by clinical symptoms and signs, along with laboratory and imaging findings. However, such clinical findings are not parallel to the disease activity of IBD and are difficult to use in treatment monitoring. Therefore, non-invasive quantitative imaging tools are required for the multiple follow-up exams of IBD patients in order to monitor the disease activity and determine treatment regimens. In this study, we evaluated a dual P- and E-selectin-targeted microbubble (MB_Selectin) in an interleukin-2 receptor α deficient (IL-2Rα^−/−) spontaneous chronic IBD mouse model for assessing long-term anti-inflammatory effects with ultrasound molecular imaging (USMI). We used IL-2Rα^−/− (male and female on a C57BL/6 genetic background; n = 39) and C57BL/6 wild-type (negative control; n = 6) mice for the study. USMI of the proximal, middle, and distal colon was performed with MB_Selectin using a small animal scanner (Vevo 2100) up to six times in each IL-2Rα^−/− mouse between 6–30 weeks of age. USMI signals were compared between IL-2Rα^−/− vs. wild-type mice, and sexes in three colonic locations. Imaged colon segments were analyzed ex vivo for inflammatory changes on H&E-stained sections and for selectin expression by immunofluorescence staining. We successfully detected spontaneous chronic colitis in IL-2Rα^−/− mice between 6–30 weeks (onset at 6–14 weeks) compared to wild-type mice. Both male and female IL-2Rα^−/− mice were equally (p = 0.996) affected with the disease, and there was no significant (p > 0.05) difference in USMI signals of colitis between the proximal, middle, and distal colon. We observed the fluctuating USMI signals in IL-2Rα^−/− mice between 6–30 weeks, which might suggest a resemblance of the remission-flare pattern of human IBD. The ex vivo H&E and immunostaining further confirmed the inflammatory changes, and the high expression of P- and E-selectin in the colon. The results of this study highlight the IL-2Rα^−/− mice as a chronic colitis model and are suitable for the long-term assessment of treatment response using a dual P- and E-selectin-targeted USMI.

Targeting memory T cell metabolism to improve immunity

Vaccination affords protection from disease by activating pathogen-specific immune cells and facilitating the development of persistent immunologic memory toward the vaccine-specific pathogen. Current vaccine regimens are often based on the efficiency of the acute immune response, and not necessarily on the generation of memory cells, in part because the mechanisms underlying the development of efficient immune memory remain incompletely understood. This Review describes recent advances in defining memory T cell metabolism and how metabolism of these cells might be altered in patients affected by mitochondrial diseases or metabolic syndrome, who show higher susceptibility to recurrent infections and higher rates of vaccine failure. It discusses how this new understanding could add to the way we think about immunologic memory, vaccine development, and cancer immunotherapy.

Specific Cytokine Profiles Predict the Severity of Influenza A Pneumonia: A Prospectively Multicenter Pilot Study

Purpose

Studying the cytokine profiles in influenza A pneumonia could be helpful to better understand the pathogenesis of the disease and predict its prognosis. Patients and Methods. Patients with influenza A pneumonia (including 2009H1N1, H1N1, H3N1, and H7N1) hospitalized in six hospitals from January 2017 to October 2018 were enrolled (ClinicalTrials.gov ID, NCT03093220). Sputum samples were collected within 24 hours after admission and subsequently analyzed for cytokine profiles using a Luminex assay.

Results

A total of 35 patients with influenza A pneumonia were included in the study. The levels of IL-6, IFN-γ, and IL-2 were increased in patients with severe influenza A pneumonia (n =10) (P = 0.002, 0.009, and 0.008, respectively), while those of IL-5, IL-25, IL-17A, and IL-22 were decreased compared to patients with nonsevere pneumonia (P = 0.0001, 0.009, 0.0001, and 0.006, respectively). The levels of IL-2 and IL-6 in the nonsurvivors (n = 5) were significantly higher than those in the survivors (P = 0.043 and 0.0001, respectively), while the levels of IL-5, IL-17A, and IL-22 were significantly lower (P = 0.001, 0.012, and 0.043, respectively). The IL-4/IL-17A ratio has the potential to be a good predictor (AUC = 0.94, P < 0.05, sensitivity = 88.89%, specificity = 92.31%) and an independent risk factor (OR, 95% CI: 3.772, 1.188-11.975; P < 0.05) for intermittent positive pressure ventilation (n = 9).

Conclusion

Significant dysregulation of cytokine profiles can be observed in patients with severe influenza A pneumonia.

Harnessing Treg Homeostasis to Optimize Posttransplant Immunity: Current Concepts and Future Perspectives

CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) are functionally distinct subsets of mature T cells with broad suppressive activity and have been shown to play an important role in the establishment of immune tolerance after allogeneic hematopoietic stem cell transplantation (HSCT). Tregs exhibit an activated phenotype from the stage of emigration from the thymus and maintain continuous proliferation in the periphery. The distinctive feature in homeostasis enables Tregs to respond sensitively to small environmental changes and exert necessary and sufficient immune suppression; however, on the other hand, it also predisposes Tregs to be susceptible to apoptosis in the inflammatory condition post-transplant. Our studies have attempted to define the intrinsic and extrinsic factors affecting Treg homeostasis from the acute to chronic phases after allogeneic HSCT. We have found that altered cytokine environment in the prolonged post-HSCT lymphopenia or peri-transplant use of immune checkpoint inhibitors could hamper Treg reconstitution, leading to refractory graft-versus-host disease. Using murine models and clinical trials, we have also demonstrated that proper intervention with low-dose interleukin-2 or post-transplant cyclophosphamide could restore Treg homeostasis and further amplify the suppressive function after HSCT. The purpose of this review is to reconsider the distinctive characteristics of post-transplant Treg homeostasis and discuss how to harness Treg homeostasis to optimize posttransplant immunity for developing a safe and efficient therapeutic strategy.

Novel Discoveries in Immune Dysregulation in Inborn Errors of Immunity

With the expansion of our knowledge on inborn errors of immunity (IEI), it gradually becomes clear that immune dysregulation plays an important part. In some cases, autoimmunity, hyperinflammation and lymphoproliferation are far more serious than infections. Thus, immune dysregulation has become significant in disease monitoring and treatment. In recent years, the wide application of whole-exome sequencing/whole-genome sequencing has tremendously promoted the discovery and further studies of new IEI. The number of discovered IEI is growing rapidly, followed by numerous studies of their pathogenesis and therapy. In this review, we focus on novel discovered primary immune dysregulation diseases, including deficiency of SLC7A7, CD122, DEF6, FERMT1, TGFB1, RIPK1, CD137, TET2 and SOCS1. We discuss their genetic mutation, symptoms and current therapeutic methods, and point out the gaps in this field.

Clean up by aisle 2: roles for IL-2 receptors in host defense and tolerance

Although IL-2 was first recognized as growth factor for T cells, it is now also appreciated to be a key regulator of T cells through its effects on regulatory T cells (Treg). The IL-2 receptor (IL-2R) subunits' different (i) ligand affinities, (ii) dimerization or trimerization relationships with other cytokine subunits, (iii) expression across multiple cell types, and (iv) downstream signaling effects, largely dictate cellular tolerance and antimicrobial processes. Defects in IL-2Rγ result in profound and almost universally fatal immune deficiency, unless treated with hematopoietic stem cell transplantation (HSCT). Defects in IL-2Rα and IL-2Rβ result in more limited infection susceptibility, particularly to herpesviruses. However, the most prominent clinical symptomatology for IL-2Rα and IL-2Rβ defects include multi-organ autoimmunity and inflammation, consistent with the critical role of IL-2 in establishing and maintaining immune tolerance. Here, we review how we have arrived at our current understanding of the complex roles of IL-2/2R in host defense and tolerance focusing on the insights gained from human clinical immunology.