Increased sIL-2Rα leads to obstruction of IL-2 biological function and Treg cells differentiation in SLE patients via binding to IL-2

IL-2 detected by flow cytometry and its significance in systemic lupus erythematosus

OBJECTIVE

Low-dose interleukin 2 (IL-2) administration has been shown to selectively modulate regulatory T (Treg) cell abundance and alleviate the progression of systemic lupus erythematosus (SLE). IL-2 level could be indicator of low-dose IL-2 usage in SLE patients. However, current methods for IL-2 detection are generally not sensitive to be used in clinic. This study aims to establish flow cytometry-based IL-2 detection as a feasible approach in determining IL-2 in peripheral blood of SLE patients.

METHODS

Flow cytometry was used to quantify the relative mean fluorescence intensity (MFI) of IL-2 in CD3+T cells and other lymphocyte subsets in peripheral blood mononuclear cell (PBMCs) from a cohort of 134 SLE patients and 112 healthy controls (HC). Correlations between IL-2 MFI and clinical or laboratory parameters in SLE patients were also investigated.

RESULTS

MFI of IL-2 represented IL-2 expression in CD3+T cells. IL-2 MFI was significantly lower in SLE patients compared to the HC group and negatively associated with anti-ribosomal protein antibodies, erythrocyte sedimentation rate (ESR), and blood urea. Conversely, it was positively correlated with IgA and hemoglobin. These associations with IgA, hemoglobin, ESR, and blood urea remained significant after adjusting for age and disease duration. IL-2 level was also positively correlated with the relative abundance of Th1, Th2, and Th17 cells. Furthermore, MFI of IL-2 recovered with effective treatment in SLE patients.

CONCLUSIONS

MFI of IL-2 serves as a feasible marker of IL-2, which is significantly decreased in SLE patients and recovered with treatment, suggesting its potential for assessing short-term disease status and treatment response in SLE patients. Key Points • IL-2 MFI can be used to estimate IL-2 expression level in SLE patients.  • IL-2 MFI is significantly reduced in SLE patients. • IL-2 MFI can serve as a marker for monitoring SLE activity and short-term status.

Low-dose IL-2 restores Tfh/Tfr imbalance and modulates B cell subset distribution in the pre-arthritis phase of the collagen-induced arthritis model

OBJECTIVE

This study is aimed at investigating the characteristics of RA patients at different stages and at evaluating the potential application of low-dose interleukin-2 (ld-IL-2) during the preclinical stage.

METHODS

Patients with undifferentiated arthritis (UA), early RA (Ea-RA), new-onset RA (New-RA), and recurrent RA (Re-RA) were included. Clinical data and laboratory parameters were collected from all participants. A comparative analysis of arthritis-related clinical features and serum levels of IL-2 and soluble IL-2 receptor (sIL-2R) was conducted. Collagen-induced arthritis (CIA) mice received ld-IL-2 on days 0, 7, 14, and 28 after primary immunisation for 4 weeks. The percentages of Treg, Tfr, Tfh, and PD-1+Tfh cells were analysed. Additionally, naive CD4+ T cells were cultured in vitro to assess the effects of IL-2 on Tfh and Tfr differentiation.

RESULTS

UA patients primarily exhibited early involvement of large joints. The sIL-2R level in UA patients was significantly lower than in those with Ea-RA, New-RA, and Re-RA and was comparable to levels in healthy controls. ld-IL-2 administration at different time points in the CIA model exerted varying effects on arthritis severity. Prophylactic ld-IL-2 administration reduced arthritis severity and incidence in CIA; it decreased the percentage of PD-1+Tfh cells while increasing Tfr cells, thereby restoring immune balance. All IL-2 intervention groups effectively reduced the Tfh/Tfr ratio and altered the distribution of B cell subsets. Mechanistically, ld-IL-2 primarily suppressed the differentiation of PD-1+Tfh cells and promoted Treg cell differentiation via STAT3 and STAT5 signalling, contributing to the restoration of immune tolerance.

CONCLUSION

These findings indicate that elevated sIL-2R levels in UA patients may predict progression to Ea-RA. Furthermore, ld-IL-2 restores immune tolerance by rebalancing Tfh/Tfr populations, highlighting its potential as a novel immunoregulatory strategy during the preclinical phase of RA. Key Points • Prophylactic low-dose IL-2 intervention reduces the severity and incidence of arthritis in the CIA model. • Low-dose IL-2 decreases the percentage of PD-1+Tfh cells while increasing Tfr cells, contributing to the restoration of immune balance.

Interleukin-2 and its receptors: Implications and therapeutic prospects in immune-mediated disorders of central nervous system

Interleukin-2 (IL-2), the first cloned cytokine, is a multifunctional molecule with diverse cellular origins. As a pivotal T-cell growth factor, IL-2 is crucial for T-cell proliferation and the generation of effector and memory cells. Besides, IL-2 and its receptor (IL-2R) are expressed in various cell types within the brain and have been implicated in the pathogenesis of several neurological disorders. In conditions characterized by primary or secondary inflammatory processes, such as multiple sclerosis, Alzheimer's disease, ischemic stroke, and encephalitis, IL-2/IL-2R expression exhibits region- and subtype-specific and variations associated with disease stages in plasma, cerebrospinal fluid (CSF), and brain tissues. These variations highlight the potential of IL-2/IL-2R as promising diagnostic and prognostic biomarkers, as well as therapeutic targets. This review provides a comprehensive summary of the roles, expression patterns, and regulatory mechanisms of IL-2/IL-2R in immune-mediated disorders of the central nervous system (CNS), with particular emphasis on the impact of genetic polymorphisms in IL-2 and IL-2R subunits on disease susceptibility and progression. In addition, the research advances in IL-2/IL-2R-targeted therapies are also discussed, offering novel insights into the immunotherapeutic strategies for CNS diseases.

Neutrophil Extracellular Traps Participate in the Pathogenesis of Lupus Through S100A10-Mediated Regulatory T-Cell Differentiation and Functional Abnormalities

In systemic lupus erythematosus (SLE), neutrophil dysregulation and neutrophil extracellular traps (NETs) formation contribute to disease pathogenesis, potentially worsening the autoimmune response. Although research indicates NETs' involvement in various autoimmune conditions, their relationship with regulatory T cells (Tregs) in SLE remains elusive. In this study, in vivo experiments were involved in administering NET injections to C57BL/6 and MRL/Ipr mice. In vitro, a co-culture system facilitated interaction between Tregs and NETs. Proteomic analysis elucidated NET composition, while RNA sequencing delineated their impact on Treg differentiation. We demonstrated that increased NET levels correlate inversely with Treg abundance in SLE patients, influencing both their proportion and functionality. NET administration reduced Treg levels and induced lupus-like symptoms in C57BL/6 mice, exacerbating symptoms in MRL/Ipr mice. DNase I treatment mitigated NET effects, restoring Treg levels and alleviating symptoms. RNA sequencing revealed altered gene expression in naïve CD4+ T cells exposed to NETs. Additionally, proteomic analysis showed S100A10 protein changes between SLE patients and healthy controls, hindering Treg differentiation. NETs influence TLR-4 of naïve CD4+ T cells via S100A10, thereby modulating Treg proportion and functionality. These findings highlight the critical role of NETs in Treg differentiation in SLE, suggesting that targeting NETs may provide a novel therapeutic approach.

A causal link between circulating immune cells and erectile dysfunction: Two-sample bidirectional Mendelian randomization study

Emerging observational studies have highlighted a robust association between circulating immune cells and erectile dysfunction (ED); however, these associations may be confounded by underlying factors. To elucidate this relationship, we conducted a comprehensive two-sample Mendelian randomization (MR) analysis to evaluate the potential causal links between circulating immune cell and ED. Utilizing large-scale genetic datasets from publicly available sources, we systematically investigated causal associations across 731 distinct immunophenotypes and ED risk, supported by rigorous sensitivity analyses to ensure robustness, evaluate heterogeneity, and detect horizontal pleiotropy. In forward MR analyses, 28 immune phenotypes were identified as having a causal association with ED. Notably, 3 specific phenotypes: CD25 + resting Treg cells, CD33dim HLA-DR + CD11b + antigen-presenting cells, and CD3- lymphocyte antigen-presenting cells, exhibited consistent significance across multiple MR methods, including inverse-variance weighted, MR-Egger, and weighted median analyses. Additionally, reverse MR analyses revealed that ED could causally influence 41 immune phenotypes, with 11 phenotypes showing consistent significance across the same analytical approaches. These findings underscore the complex bidirectional relationship between circulating immune cells and ED, providing critical insights into ED pathogenesis and potential targets for novel therapeutic interventions.

Serum soluble interleukin-2 receptor alpha may predict tubulointerstitial inflammatory cell infiltration and short-term disease progression in immunoglobin A nephropathy

This study aims to explore the relationship between serum soluble interleukin-2 receptor alpha (sIL-2Rα) levels and histologic features in immunoglobin A nephropathy (IgAN), and evaluate its predicting values on disease progression and remission status. IgAN patients were included retrospectively. Lee classification, Oxford classification and histological scoring were evaluated. Patients' estimated filtration rate (eGFR) and proteinuria remission status were collected during 6-month follow-up. Logistic regression was used to determine the risk factors and predicting value. Receiver operating characteristic (ROC) curve were used to determine the predicting value for outcome. One hundred seventy-two subjects were included in this study. Individuals in moderate-to-severe tubulointerstitial inflammatory cell infiltration group manifested with significantly elevated serum sIL-2Rα levels than those in non-to-mild group. Serum sIL-2Rα levels were positively correlated with infiltration scores. Serum sIL-2Rα was an independent risk factor for moderate-to-severe inflammatory cell infiltration [sIL-2Rα: OR 1.29 (1.015-1.640, p = 0.038)]. ROC curve analysis regarding predictive value for moderate-to-severe inflammatory cell infiltration of sIL-2Rα suggested area under curve was 0.859 (0.801-0.918, p = 0.000) when sIL-2Rα combined with eGFR < 60 mL/(min·1.73 m2), 24-h proteinuria excretion > 1.0 g, and hemoglobin. It showed good sensitivity (71.6%) and specificity (87.6%). Additionally, sIL-2Rα levels at kidney biopsy were strong predictive factor for kidney function loss 6 months after kidney biopsy [OR 4.161 (1.013-17.088, p = 0.048)]. High serum sIL-2Rα was significantly associated with serious inflammatory cell infiltration in IgAN, and it showed strong predictive value for disease prognosis. Serum sIL-2Rα could be a useful noninvasive biomarker to evaluate the extent of histological injury and disease prognosis in IgAN.

Th1-related transcription factors and cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory disorder related to immunity dysfunction. The Th1 cell family including Th1 cells, transcription factor T-bet, and related cytokines IFNγ, TNFα, IL-2, IL-18, TGF-β, and IL-12 have been widely discussed in autoimmunity, such as SLE. In this review, we will comprehensively discuss the expression profile of the Th1 cell family in both SLE patients and animal models and clarify how the family members are involved in lupus development. Interestingly, T-bet-related age-associated B cells (ABCs) and low-dose IL-2 treatment in lupus were emergently discussed as well. Collection of the evidence will better understand the roles of the Th1 cell family in lupus pathogenesis, especially targeting IL-2 in lupus.

Role of IL-2/IL-2 receptor in pathogenesis of autoimmune disorders: Genetic and therapeutic aspects

Interleukin-2 (IL-2) is an important cytokine that plays a key role in the immune response. The IL-2 receptor (IL-2R) is composed of three subunits, alpha, beta, and gamma, with the alpha subunit having the highest affinity for IL-2. Several studies reported that immune dysregulation of IL-2 may cause tissue injury as well as damage leading to the pathogenesis of various autoimmune diseases such as acute necrotizing vasculitis in systemic lupus erythematosus (SLE), inflammatory synovitis in rheumatoid arthritis (RA), salivary and lacrimal gland dys-function in Sjogren syndrome (SS), obliterative vasculopathy fibrosis in systemic sclerosis (SSc), and inflammatory demyelination in multiple sclerosis (MS). The aim of this review paper was to examine the role of IL-2/IL-2R in various autoimmune disorders, taking into account recent advancements and discoveries, gaps in the current literature, ongoing debates, and potential avenues for future research. The focus of this review is on systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, sjogren syndrome, and multiple sclerosis, which are all linked to the malfunctioning of IL-2/IL-2R. In genetic studies, gene polymorphisms of IL-2 such as IL-2 330/T, IL-2 330/G, and rs2069763 are involved in increasing the risk of SLE. Furthermore, genetic associations of IL-2/IL-2R such as rs791588, rs2281089, rs2104286, rs11594656, and rs35285258 are significantly associated with RA susceptibility. The IL-2 polymorphism including rs2069762A, rs6822844T, rs6835457G, and rs907715T are significant connections with systemic sclerosis. In addition, rs2104286 (IL-2), rs11594656 (IL-2RA), rs35285258 (IL-2RB) gene polymorphism significant increases the risk of multiple sclerosis. In therapeutic approaches, low-dose IL-2 therapy could regulate Tfr and Tfh cells, resulting in a reduction in disease activity in the SLE patients. In addition, elevated sIL-2R levels in the peripheral blood of SLE patients could be linked to an immunoregulatory imbalance, which may contribute to the onset and progression of SLE. Consequently, sIL-2R could potentially be a target for future SLE therapy. Moreover, Low dose-IL2 was well-tolerated, and low levels of Treg and high levels of IL-21 were associated with positive responses to Ld-IL2 suggested to be a safe and effective treatment for RA. Additionally, low-dose IL-2 treatment improves the exocrine glands' ability to secrete saliva in SS-affected mice. Whereas, Basiliximab targets the alpha chain of the IL-2 receptor suggested as a potential treatment for SSc. Also, pre-and post-treatment with Tregs, MDSCs, and IL-2 may have the potential to prevent EAE induction in patients with MS. It is suggested that further studies should be conducted on IL-2 polymorphism in Sjogren syndrome.

Low-dose interleukin-2 treatment increases the proportion of regulatory T cells in patients with rheumatic diseases: A meta-analysis

BACKGROUND

It is now accepted that immune tolerance disorders caused by inadequate Treg cell function or number are important factors in the development and progression of rheumatic diseases. There is increasing evidence that ld IL-2 treatment increases the proportion of Treg cells in patients' peripheral blood, but this conclusion is still controversial. Here, we performed a meta-analysis of reports documenting the proportion of Treg cells and the rate of adverse events in patients with rheumatic disease before and after the administration of ld IL-2 to better understand its effect and safety on Treg cells in the field of rheumatic diseases.

METHODS

We systematically searched PubMed, Embase, Scopus, Cochrane Library, and Web of science databases up to 15th November 2022 and identified studies that reported the proportion of peripheral blood Treg cells before and after ld IL-2 treatment in patients with rheumatic disease. Random-effects model was used to perform a meta-analysis of Treg cell proportions before and after ld IL-2 administration, and a meta-regression analysis was performed to explore heterogeneity. Inconsistency was evaluated using the I-squared index (I²), and publication bias was assessed by examining funnel plot asymmetry using the Egger tests.

RESULTS

Eighteen studies involving 1608 patients were included in the meta-analysis. The proportion of Treg cells in peripheral blood of these patients increased significantly after receiving ld IL-2 treatment [1.07 (95% CI 0.86,1.27), p < 0.001, I² = 67.3%]. Next, Meta-regression was performed for 5 variables including publish year, disease type, trail type and dosage and duration of the medication. The results suggest that these variables do not lead to high heterogeneity. (p = 0.698, 0.267, 0.502, 0.843, 0.560, respectively). And finally, statistical analysis showed no difference in adverse reactions between ld IL-2 group and control group in treatment [1.06 (95% CI 0.86,1.31), p = 0.586, I2 = 53.8%], which is unreliable because the data is so small.

CONCLUSIONS

Ld IL-2 does increase the proportion of peripheral blood Treg cells in patients with rheumatism, and single and cumulative doses must be considered when using ld IL-2. In addition, more studies on the safety of ld IL-2 are urgently needed.