Elevated transferrin receptor impairs T cell metabolism and function in systemic lupus erythematosus

Mitochondrial fatty acid synthesis and MECR regulate CD4+ T cell function and oxidative metabolism

Imbalanced effector and regulatory CD4+ T cell subsets drive many inflammatory diseases. These T cell subsets rely on distinct metabolic programs, modulation of which differentially affects T cell fate and function. Lipid metabolism is fundamental yet remains poorly understood across CD4+ T cell subsets. Therefore, we performed targeted in vivo CRISPR/Cas9 screens to identify lipid metabolism genes and pathways essential for T cell functions. These screens established mitochondrial fatty acid synthesis genes Mecr, Mcat, and Oxsm as key metabolic regulators. Of these, the inborn error of metabolism gene Mecr was most dynamically regulated. Mecrfl/fl; Cd4cre mice had normal naïve CD4+ and CD8+ T cell numbers, demonstrating that MECR is not essential in homeostatic conditions. However, effector and memory T cells were reduced in Mecr knockout and MECR-deficient CD4+ T cells and proliferated, differentiated, and survived less well than control T cells. Interestingly, T cells ultimately showed signs of mitochondrial stress and dysfunction in the absence of MECR. Mecr-deficient T cells also had decreased mitochondrial respiration, reduced tricarboxylic acid intermediates, and accumulated intracellular iron, which appeared to contribute to increased cell death and sensitivity to ferroptosis. Importantly, MECR-deficient T cells exhibited fitness disadvantages and were less effective at driving disease in an in vivo model of inflammatory bowel disease. Thus, MECR-mediated metabolism broadly supports CD4+ T cell proliferation and survival in vivo. These findings may also provide insight to the immunological state of MECR- and other mitochondrial fatty acid synthesis-deficient patients.

Downregulation of AATK enhances susceptibility to ferroptosis by promoting endosome recycling in gefitinib-resistant lung cancer cells

Ferroptosis has been characterised by disruption of the cell membrane through iron-related lipid peroxidation. However, regulation of iron homeostasis in lung cancer cells that are resistant to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) remains unclear. Transcriptome analysis identified a significant downregulation of apoptosis-associated tyrosine kinase (AATK) mRNA expression in gefitinib-resistant PC9 (PC9-GR) cells, which were found to be more susceptible to ferroptosis inducers. An in-depth analysis of publicly available datasets revealed that downregulation of AATK mRNA was associated with lymph node metastasis and poor prognosis in patients with lung adenocarcinoma. Knockdown of AATK-sensitised PC9, HCC827, and H441 cells to the ferroptosis inducer RSL3, whereas ectopic expression of AATK reduced RSL3-induced cell death in PC9-GR and HCC827-GR cells. Compared to PC9 cells, PC9-GR cells exhibited higher transferrin uptake, endosome recycling rate, and increased intracellular iron levels. Blocking iron transport reduced RSL3-induced ferroptosis in PC9-GR cells. Mechanistic studies showed that AATK localised to both early and recycling endosomes. Knockdown of AATK facilitated endosome recycling and elevated intracellular ferrous iron (Fe2+) levels in PC9 cells. Conversely, ectopic expression of AATK delayed endosome recycling and reduced intracellular Fe2+ levels in PC9-GR cells. Inhibition of AATK downregulation-induced iron accumulation decreased RSL3-induced ferroptosis. Taken together, our study indicates that the downregulation of AATK contributes to endosome recycling and iron accumulation, leading to an increased susceptibility to ferroptosis in EGFR-TKI-resistant lung cancer cells. © 2025 The Pathological Society of Great Britain and Ireland.

CD4+ T-cell metabolism in the pathogenesis of Sjogren's syndrome

The abnormal effector function of CD4+ T cells plays a key role in the pathogenesis of Sjogren's syndrome (SS) and its associated systematic autoimmune response. Cellular metabolism, including glucose metabolism, lipid metabolism and amino acid metabolism, supports proliferation, migration, survival and differentiation into distinct CD4+ T-cell subsets. Different subtypes of T cells have significantly different demands for related metabolic processes, which enables us to finely regulate CD4+ T cells through different metabolic processes in autoimmune diseases such as SS. In this review, we summarize the effects of disturbances in distinct metabolic processes, such as glycolysis, fatty acid metabolism, glutamine decomposition, mitochondrial dynamics, and ferroptosis, on how to support the effector functions of CD4+ T cells in the SS. We also discuss potential drugs with high value in the treatment of SS through metabolic normalization in CD4+ T cells. Finally, we propose possible directions for future targeted therapy for immunometabolism in SS.

Iron and energy metabolic interactions in Treg-mediated immune regulation

Immunometabolism, the study of how metabolic processes influence immune cell function, has emerged as a critical field in understanding the regulation of immune tolerance and the pathological mechanisms underlying autoimmune diseases. Intracellular metabolic pathways not only provide the necessary energy for immune cell survival and activity but also shape the differentiation, phenotype, proliferation, and effector functions of immune cells. This is particularly evident in CD4+ Foxp3+ regulatory T cells (Treg), which are pivotal for maintaining immune homeostasis and preventing autoimmune reactions. Strong experimental evidence highlights the profound impact of metabolism on Treg. Their anti-inflammatory function and ability to suppress excessive immune responses depend on the integration of metabolic cues with their transcriptional and signaling networks. Iron metabolism and mitochondrial dynamics are among the key factors influencing Treg function. This review focuses on how iron and mitochondrial metabolism shape Treg biology and function.

Identification of RSAD2 as a Key Biomarker Linking Iron Metabolism and Dendritic Cell Activation in Systemic Lupus Erythematosus Through Bioinformatics and Experimental Validation

Background

Systemic lupus erythematosus (SLE) is characterized by aberrant immune activation and disrupted iron metabolism, yet the molecular mediators that govern both processes remain unclear. This study aims to identify pivotal genes that modulate immune responses and iron metabolism, and to delineate their contributions to SLE pathogenesis.

Methods

Differentially expressed genes related to iron metabolism (IM-DEGs) were identified using datasets (GSE72326, GSE110169, GSE126307, and GSE50772) from the GEO database and the MSigDB. Functional enrichment analyses were performed on the iron metabolism related genes (IM-Genes). A weighted gene co-expression network analysis was constructed to identify hub genes, which were further refined as potential biomarkers using the least absolute shrinkage and selection operator method. The predictive value of these biomarkers was validated using receiver operating characteristic (ROC) curves and the nomogram. CIBERSORT was employed to evaluate immune cell infiltration in SLE. Additionally, the expression and function of RSAD2 were confirmed using RNA interference, quantitative real-time PCR, and Western blotting techniques.

Results

Bioinformatics analyses identified 4 potential biomarkers: RSAD2, MT2A, LCN2, and LTF. RSAD2 exhibited the highest clinical validity (AUC = 0.927) and was closely associated with classic diagnostic indicators. Its diagnostic potential was confirmed through ROC curve and nomogram, highlighting its role in SLE pathogenesis. Elevated RSAD2 expression was observed in peripheral blood mononuclear cells of SLE patients, positively correlating with activated dendritic cells (DCs). Notably, Rsad2 knockdown markedly impaired the function of activated DCs, as evidenced by suppressed expression of inflammatory mediators and iron metabolism-related genes.

Conclusion

Our findings suggest that RSAD2 is a potential diagnostic biomarker and therapeutic target for SLE, elucidating the intricate relationship between immune dysregulation and aberrant iron metabolism in activated DCs, which exacerbates SLE.

Ferroptosis of T cell in inflammation and tumour immunity

Ferroptosis is an innovative concept defined as a distinct programmed cell death mode regulated by iron-dependent lipid peroxidation accumulation. This process is governed by numerous energy metabolites such as fatty acids, amino acids and glucose, as well as iron homeostasis. In recent years, increasing studies have been devoted to the crucial effects of ferroptosis in immune cells during the pathogenesis of diseases such as infections, tumours and autoimmune disorders. This review summarises the latest advancements in T-cell ferroptosis, addresses the key components and mechanism of ferroptosis in T cells during inflammatory conditions and tumour progression, and highlights the potential target for treating related diseases. KEY POINTS: Ferroptosis-related mechanisms significantly affect the biology of CD4+ T-cell subsets and are further involved in inflammatory diseases. Crosstalk between CD8+ T cells and tumour cells induces ferroptosis in the tumour microenvironment. Glutathione peroxidase 4 loss promotes regulatory T-cell ferroptosis to enhance anti-tumour immunity.

Recent advances in immunometabolism in rheumatic diseases

PURPOSE OF REVIEW

Aberrant autoreactive innate and adaptive immune responses cause systemic autoimmune diseases. Autoimmunity has been linked to abnormal metabolic states, and immunometabolism has emerged as a critical field in understanding the pathogenesis of rheumatic diseases. We aimed to explore the latest research on metabolic reprogramming in various immune cell types, including T cells, B cells, neutrophils, dendritic cells, monocytes, and macrophages, in the context of rheumatic diseases.

RECENT FINDINGS

Each immune cell utilizes preferred metabolic pathways, and the cell activation dramatically modifies metabolic status. The inhibition of these pathways alters cell survival, differentiation, proliferation, and cytokine production - all of which contribute to rheumatic disease progression.

SUMMARY

Targeting metabolic pathways or introducing anti-inflammatory metabolites, such as itaconate, could be novel therapeutic strategies for rheumatic diseases. Further research should focus on strategies for translating basic research findings to bedside applications.

Iron Drives Eosinophil Differentiation in Allergic Airway Inflammation Through Mitochondrial Metabolic Adaptation

Eosinophils play a crucial role as effector cells in asthma pathogenesis, with their differentiation being tightly regulated by metabolic mechanisms. While the involvement of iron in various cellular processes is well known, its specific role in eosinophil differentiation has largely remained unexplored. This study demonstrates that iron levels are increased during the differentiation process from eosinophil progenitors to mature and activated eosinophils in the context of allergic airway inflammation. Through experiments involving iron chelators, supplements, and iron-deficient or iron-enriched diets, the indispensable role of iron in eosinophil lineage commitment both in vitro and in vivo is demonstrated. Remarkably, iron chelation effectively suppresses eosinophil differentiation and alleviates airway inflammation in a house dust mite(HDM)-induced mouse model of allergic asthma. Mechanistically, iron promotes the expression of transcription factors that enforce eosinophil differentiation, and maintains mitochondrial metabolic activities, leading to specific metabolic shifts within the tricarboxylic acid (TCA) cycle, with succinate promoting eosinophil differentiation. Overall, this study highlights the function of iron and underlying metabolic mechanisms in eosinophil differentiation, providing potential therapeutic strategies for asthma control.

Intricating connections: the role of ferroptosis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory and autoimmune disease with multiple tissue damage. However, the pathology remains elusive, and effective treatments are lacking. Multiple types of programmed cell death (PCD) implicated in SLE progression have recently been identified. Although ferroptosis, an iron-dependent form of cell death, has numerous pathophysiological features similar to those of SLE, such as intracellular iron accumulation, mitochondrial dysfunction, lipid metabolism disorders and concentration of damage associated-molecular patterns (DAMPs), only a few reports have demonstrated that ferroptosis is involved in SLE progression and that the role of ferroptosis in SLE pathogenesis continues to be neglected. Therefore, this review elucidates the potential intricate relationship between SLE and ferroptosis to provide a reliable theoretical basis for further research on ferroptosis in the pathogenesis of SLE.

Iron improves the antiviral activity of NK cells

Natural killer (NK) cells are innate immune cells that play a crucial role as a first line of defense against viral infections and tumor development. Iron is an essential nutrient for immune cells, but it can also pose biochemical risks such as the production of reactive oxygen species. The importance of iron for the NK cell function has gained increasing recognition. We have previously shown that NK cells require iron to efficiently eliminate virus-infected target cells; however, the impact of nutritional iron deficiency on NK cell function and the therapeutic benefits of iron supplementation remain unclear. Here, we demonstrate that diet-related low iron levels lead to increased retroviral loads due to functional NK cell impairment, while iron supplementation enhances NK cell proliferation, as well as their cytotoxic efficacy. Notably, iron-treated NK cells exhibited significant metabolic changes, including mitochondrial reorganization. Interestingly, although iron supplementation decreased the NK cell's cytokine production, it significantly improved NK cell degranulation and the expression of cytotoxicity-associated proteins. These findings highlight the critical role of iron in maintaining NK cell immunity and suggest that iron supplementation may hold therapeutic potential for supporting the treatment of viral infections and immunodeficiency disorders.

Research advancements in the association between prevalent trace metals and connective tissue diseases

Connective tissue diseases (CTD) encompass a spectrum of autoimmune disorders, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS), inflammatory myopathy (IIM), systemic sclerosis (SSc), among others. Recent research has highlighted the significant role of trace metals in the pathogenesis of connective tissue diseases. This article provides an overview of recent advancements in understanding the correlation between common trace metals such as iron, copper, zinc and CTD, aiming to offer novel insights for the diagnosis and treatment of these conditions. Iron is implicated in the pathogenesis of SLE through various mechanisms, including alterations in serum iron concentration, disturbances in iron metabolism and homeostasis, as well as involvement in ferroptosis. Disorders affecting iron metabolism, ferroptosis, and the expression and regulation of associated genes and proteins contribute to the development and progression of RA. Elevated serum copper levels are observed in patients with both SLE and RA compared to healthy controls. Cuproptosis, a novel form of cell death, is also considered to be linked to their pathogenesis. Decreased serum zinc concentration is evident in patients with SLE, RA, and SS. Zinc finger proteins play a crucial role in the pathogenesis of these diseases.

Immune imbalance in Lupus Nephritis: The intersection of T-Cell and ferroptosis

Ferroptosis is a novel form of cell death characterized by unlimited accumulation of iron-dependent lipid peroxides. It is often accompanied by disease, and the relationship between ferroptosis of immune cells and immune regulation has been attracting increasing attention. Initially, it was found in cancer research that the inhibition of regulatory T cell (Treg) ferroptosis and the promotion of CD8+ T cell ferroptosis jointly promoted the formation of an immune-tolerant environment in tumors. T-cell ferroptosis has subsequently been found to have immunoregulatory effects in other diseases. As an autoimmune disease characterized by immune imbalance, T-cell ferroptosis has attracted attention for its potential in regulating immune balance in lupus nephritis. This article reviews the metabolic processes within different T-cell subsets in lupus nephritis (LN), including T follicular helper (TFH) cells, T helper (Th)17 cells, Th1 cells, Th2 cells, and Treg cells, and reveals that these cellular metabolisms not only facilitate the formation of a T-cell immune imbalance but are also closely associated with the occurrence of ferroptosis. Consequently, we hypothesize that targeting the metabolic pathways of ferroptosis could become a novel research direction for effectively treating the immune imbalance in lupus nephritis by altering T-cell differentiation and the incidence of ferroptosis.

Why cells need iron: a compendium of iron utilisation

Iron deficiency is globally prevalent, causing an array of developmental, haematological, immunological, neurological, and cardiometabolic impairments, and is associated with symptoms ranging from chronic fatigue to hair loss. Within cells, iron is utilised in a variety of ways by hundreds of different proteins. Here, we review links between molecular activities regulated by iron and the pathophysiological effects of iron deficiency. We identify specific enzyme groups, biochemical pathways, cellular functions, and cell lineages that are particularly iron dependent. We provide examples of how iron deprivation influences multiple key systems and tissues, including immunity, hormone synthesis, and cholesterol metabolism. We propose that greater mechanistic understanding of how cellular iron influences physiological processes may lead to new therapeutic opportunities across a range of diseases.

The immune landscape of the inflamed joint defined by spectral flow cytometry

Cellular phenotype and function are altered in different microenvironments. For targeted therapies it is important to understand site-specific cellular adaptations. Juvenile idiopathic arthritis (JIA) is characterized by autoimmune joint inflammation, with frequent inadequate treatment responses. To comprehensively assess the inflammatory immune landscape, we designed a 37-parameter spectral flow cytometry panel delineating mononuclear cells from JIA synovial fluid (SF) of autoimmune inflamed joints, compared to JIA and healthy control blood. Synovial monocytes and NK cells (CD56bright) lack Fc-receptor CD16, suggesting antibody-mediated targeting may be ineffective. B cells and DCs, both in small frequencies in SF, undergo maturation with high 4-1BB, CD71, CD39 expression, supporting T-cell activation. SF effector and regulatory T cells were highly active with newly described co-receptor combinations that may alter function, and suggestion of metabolic reprogramming via CD71, TNFR2, and PD-1. Most SF effector phenotypes, as well as an identified CD4-Foxp3+ T-cell population, were restricted to the inflamed joint, yet specific SF-predominant CD4+ Foxp3+ Treg subpopulations were increased in blood of active but not inactive JIA, suggesting possible recirculation and loss of immunoregulation at distal sites. This first comprehensive dataset of the site-specific inflammatory landscape at protein level will inform functional studies and the development of targeted therapeutics to restore immunoregulatory balance and achieve remission in JIA.

Targeting ferroptosis in autoimmune diseases: Mechanisms and therapeutic prospects

Ferroptosis is a form of regulated cell death that relies on iron and exhibits unique characteristics, including disrupted iron balance, reduced antioxidant defenses, and abnormal lipid peroxidation. Recent research suggests that ferroptosis is associated with the onset and progression of autoimmune disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and multiple sclerosis (MS). However, the precise effects and molecular mechanisms remain incompletely understood. This article presents an overview of how ferroptosis mechanisms contribute to the development and advancement of autoimmune diseases, as well as the involvement of various immune cells in linking ferroptosis to autoimmune conditions. It also explores potential drug targets within the ferroptosis pathway and recent advancements in therapeutic approaches aimed at preventing and treating autoimmune diseases by targeting ferroptosis. Lastly, the article discusses the challenges and opportunities in utilizing ferroptosis as a potential therapeutic avenue for autoimmune disorders.

Insights from CD71 presentation and serum lipid peroxidation in myasthenia gravis - A small cohort study

Myasthenia gravis (MG) is a multifaceted autoimmune disorder affecting the postsynaptic neuromuscular junction. In this study, we examined CD4+ and CD8+ T lymphocyte levels and ratios within peripheral blood mononuclear cells (PBMCs) in MG patients. Additionally, we assessed lymphocytes for the expression of CD71, which functions as a transferrin receptor mediating the uptake of iron into the cells. Building on recent discussions regarding CD20 depletion treatments in MG, we also scrutinized lymphocytes for CD20 expression. Comparative analyses were conducted among healthy controls, newly diagnosed MG patients, those undergoing pyridostigmine treatment alone, and MG patients receiving combination therapies. In the patients, the ratio of CD3+CD4+ T lymphocytes to CD3+ T lymphocytes was found to be decreased compared to the healthy controls, while the ratio of CD3+CD8+ cells to CD3+CD4+ cells increased. An increase in the percentage of CD71-expressing lymphocytes was observed in MG patients compared to the healthy control group, while CD20+ lymphocytes exhibited no statistical changes. Moreover, heightened serum lipid peroxidation levels were found in MG patients. These results suggest a possible relationship between iron metabolism, levels of CD71-expressing cells, and lipid peroxidation in MG. Conversely, pyridostigmine treatment reduced the levels of CD71-expressing cells and lipid peroxidation, suggesting potential immunomodulatory and antioxidant impacts of pyridostigmine in MG, either directly or indirectly.

Glycolysis inhibition functionally reprograms T follicular helper cells and reverses lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease in which the production of pathogenic autoantibodies depends on T follicular helper (T FH ) cells. This study was designed to investigate the mechanisms by which inhibition of glycolysis with 2-deoxy-d-glucose (2DG) reduces the expansion of T FH cells and the associated autoantibody production in lupus-prone mice. Integrated cellular, transcriptomic, epigenetic and metabolic analyses showed that 2DG reversed the enhanced cell expansion and effector functions, as well as mitochondrial and lysosomal defects in lupus T FH cells, which include an increased chaperone-mediated autophagy induced by TLR7 activation. Importantly, adoptive transfer of 2DG-reprogrammed T FH cells protected lupus-prone mice from disease progression. Orthologs of genes responsive to 2DG in murine lupus T FH cells were overexpressed in the T FH cells of SLE patients, suggesting a therapeutic potential of targeting glycolysis to eliminate aberrant T FH cells and curb the production of autoantibodies inducing tissue damage.

Androgen signaling restricts glutaminolysis to drive sex-specific Th17 metabolism in allergic airway inflammation

Female individuals have an increased prevalence of many Th17 cell-mediated diseases, including asthma. Androgen signaling decreases Th17 cell-mediated airway inflammation, and Th17 cells rely on glutaminolysis. However, it remains unclear whether androgen receptor (AR) signaling modifies glutamine metabolism to suppress Th17 cell-mediated airway inflammation. We show that Th17 cells from male humans and mice had decreased glutaminolysis compared with female individuals, and that AR signaling attenuated Th17 cell mitochondrial respiration and glutaminolysis in mice. Using allergen-induced airway inflammation mouse models, we determined that females had a selective reliance upon glutaminolysis for Th17-mediated airway inflammation, and that AR signaling attenuated glutamine uptake in CD4+ T cells by reducing expression of glutamine transporters. In patients with asthma, circulating Th17 cells from men had minimal reliance upon glutamine uptake compared to Th17 cells from women. AR signaling thus attenuates glutaminolysis, demonstrating sex-specific metabolic regulation of Th17 cells with implications for Th17 or glutaminolysis targeted therapeutics.

Ironing Out the Kinks: Arming Natural Killer Cells against Ovarian Cancer

Ameliorating the tumor immune microenvironment is a key strategy to improve the therapeutic outcomes of patients with cancer. Sandoval and colleagues demonstrate that iron chelation enhances type I IFN production, promotes NK cell tumor trafficking and activation, and synergizes with chemotherapy drug cisplatin to reduce metastatic ovarian cancer progression in murine models. See related article by Sandoval et al., p. 1901.

Subset-specific mitochondrial stress and DNA damage shape T cell responses to fever and inflammation

Heat is a cardinal feature of inflammation, yet its impacts on immune cells remain uncertain. We show that moderate-grade fever temperatures (39°C) increased murine CD4 T cell metabolism, proliferation, and inflammatory effector activity while decreasing regulatory T cell suppressive capacity. However, heat-exposed T helper 1 (TH1) cells selectively developed mitochondrial stress and DNA damage that activated Trp53 and stimulator of interferon genes pathways. Although many TH1 cells subjected to such temperatures died, surviving TH1 cells exhibited increased mitochondrial mass and enhanced activity. Electron transport chain complex 1 (ETC1) was rapidly impaired under fever-range temperatures, a phenomenon that was specifically detrimental to TH1 cells. TH1 cells with elevated DNA damage and ETC1 signatures were also detected in human chronic inflammation. Thus, fever-relevant temperatures disrupt ETC1 to selectively drive apoptosis or adaptation of TH1 cells to maintain genomic integrity and enhance effector functions.

Promising roles of combined therapy based on immune response and iron metabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an intricate autoimmune disease with diverse manifestations. Immunometabolism reprogramming contributes to the progression of SLE by regulating the phenotype and function of immune cells. Dysregulated iron metabolism is implicated in SLE pathogenesis, affecting both systemic and immune cell-specific iron homeostasis. This review explores the systemic and cellular iron handling and regulation. Additionally, the advancements regarding iron metabolism in SLE with a focus on the distinct subsets of immune cells are highlighted. By gaining insight into the interplay between iron dysregulation and immune dysfunction, the potential therapeutic avenues may be unveiled. However, challenges remain in elucidating cell-specific iron metabolic reprogramming and its contribution to SLE pathogenesis needs further research for personalized therapeutic interventions and biomarker discovery. This review provides an in-depth understanding of immune cell-specific regulatory mechanisms of iron metabolism and new insights in current challenges as well as possible clinical applications.

Reverse aging to treat lupus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multifaceted pathogenetic processes, including abnormalities of T-cell subset distribution and function. Accumulation of senescent CD4+ T cells has been found to contribute to the development of the disease. In this issue, Jiang et al. provide compelling evidence that links an expanded pool of CD4+CD57+ senescent T cells in patients with SLE to disease activity favored by interleukin-15. Importantly, treatment of lupus-prone mice with a senolytic drug resulted in decreased autoimmune pathology. The findings of this study suggest possible novel therapeutics to treat patients with SLE.

Functional overlap of inborn errors of immunity and metabolism genes defines T cell metabolic vulnerabilities

Inborn errors of metabolism (IEMs) and immunity (IEIs) are Mendelian diseases in which complex phenotypes and patient rarity have limited clinical understanding. Whereas few genes have been annotated as contributing to both IEMs and IEIs, immunometabolic demands suggested greater functional overlap. Here, CRISPR screens tested IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable previously unappreciated crossover. Analysis of IEMs showed that N-linked glycosylation and the hexosamine pathway enzyme Gfpt1 are critical for T cell expansion and function. Further, T helper (TH1) cells synthesized uridine diphosphate N-acetylglucosamine more rapidly and were more impaired by Gfpt1 deficiency than TH17 cells. Screening IEI genes found that Bcl11b promotes the CD4 T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. Thus, a high degree of functional overlap exists between IEM and IEI genes, and immunometabolic mechanisms may underlie a previously underappreciated intersection of these disorders.

Immunometabolism of ferroptosis in the tumor microenvironment

Ferroptosis is an iron-dependent form of cell death that results from excess lipid peroxidation in cellular membranes. Within the last decade, physiological and pathological roles for ferroptosis have been uncovered in autoimmune diseases, inflammatory conditions, infection, and cancer biology. Excitingly, cancer cell metabolism may be targeted to induce death by ferroptosis in cancers that are resistant to other forms of cell death. Ferroptosis sensitivity is regulated by oxidative stress, lipid metabolism, and iron metabolism, which are all influenced by the tumor microenvironment (TME). Whereas some cancer cell types have been shown to adapt to these stressors, it is not clear how immune cells regulate their sensitivities to ferroptosis. In this review, we discuss the mechanisms of ferroptosis sensitivity in different immune cell subsets, how ferroptosis influences which immune cells infiltrate the TME, and how these interactions can determine epithelial-to-mesenchymal transition (EMT) and metastasis. While much focus has been placed on inducing ferroptosis in cancer cells, these are important considerations for how ferroptosis-modulating strategies impact anti-tumor immunity. From this perspective, we also discuss some promising immunotherapies in the field of ferroptosis and the challenges associated with targeting ferroptosis in specific immune cell populations.

The immunology of systemic lupus erythematosus

Understanding the pathogenesis and clinical manifestations of systemic lupus erythematosus (SLE) has been a great challenge. Reductionist approaches to understand the nature of the disease have identified many pathogenetic contributors that parallel clinical heterogeneity. This Review outlines the immunological control of SLE and looks to experimental tools and approaches that are improving our understanding of the complex contribution of interacting genetics, environment, sex and immunoregulatory factors and their interface with processes inherent to tissue parenchymal cells. Efforts to advance precision medicine in the care of patients with SLE along with treatment strategies to correct the immune system hold hope and are also examined.

Intersection of the microbiome and immune metabolism in lupus

Systemic lupus erythematosus is a complex autoimmune disease resulting from a dysregulation of the immune system that involves gut dysbiosis and an altered host cellular metabolism. This review highlights novel insights and expands on the interactions between the gut microbiome and the host immune metabolism in lupus. Pathobionts, invasive pathogens, and even commensal microbes, when in dysbiosis, can all trigger and modulate immune responses through metabolic reprogramming. Changes in the microbiota's global composition or individual taxa may trigger a cascade of metabolic changes in immune cells that may, in turn, reprogram their functions. Factors contributing to dysbiosis include changes in intestinal hypoxia, competition for glucose, and limited availability of essential nutrients, such as tryptophan and metal ions, all of which can be driven by host metabolism changes. Conversely, the accumulation of some host metabolites, such as itaconate, succinate, and free fatty acids, could further influence the microbial composition and immune responses. Overall, mounting evidence supports a bidirectional relationship between host immunometabolism and the microbiota in lupus pathogenesis.

Advances in research on immunocyte iron metabolism, ferroptosis, and their regulatory roles in autoimmune and autoinflammatory diseases

Autoimmune diseases commonly affect various systems, but their etiology and pathogenesis remain unclear. Currently, increasing research has highlighted the role of ferroptosis in immune regulation, with immune cells being a crucial component of the body's immune system. This review provides an overview and discusses the relationship between ferroptosis, programmed cell death in immune cells, and autoimmune diseases. Additionally, it summarizes the role of various key targets of ferroptosis, such as GPX4 and TFR, in immune cell immune responses. Furthermore, the release of multiple molecules, including damage-associated molecular patterns (DAMPs), following cell death by ferroptosis, is examined, as these molecules further influence the differentiation and function of immune cells, thereby affecting the occurrence and progression of autoimmune diseases. Moreover, immune cells secrete immune factors or their metabolites, which also impact the occurrence of ferroptosis in target organs and tissues involved in autoimmune diseases. Iron chelators, chloroquine and its derivatives, antioxidants, chloroquine derivatives, and calreticulin have been demonstrated to be effective in animal studies for certain autoimmune diseases, exerting anti-inflammatory and immunomodulatory effects. Finally, a brief summary and future perspectives on the research of autoimmune diseases are provided, aiming to guide disease treatment strategies.

Iron capture through CD71 drives perinatal and tumor-associated Treg expansion

Besides suppressing immune responses, regulatory T cells (Tregs) maintain tissue homeostasis and control systemic metabolism. Whether iron is involved in Treg-mediated tolerance is completely unknown. Here, we showed that the transferrin receptor CD71 was upregulated on activated Tregs infiltrating human liver cancer. Mice with a Treg-restricted CD71 deficiency spontaneously developed a scurfy-like disease, caused by impaired perinatal Treg expansion. CD71-null Tregs displayed decreased proliferation and tissue-Treg signature loss. In perinatal life, CD71 deficiency in Tregs triggered hepatic iron overload response, characterized by increased hepcidin transcription and iron accumulation in macrophages. Lower bacterial diversity, and reduction of beneficial species, were detected in the fecal microbiota of CD71 conditional knockout neonates. Our findings indicate that CD71-mediated iron absorption is required for Treg perinatal expansion and is related to systemic iron homeostasis and bacterial gut colonization. Therefore, we hypothesize that Tregs establish nutritional tolerance through competition for iron during bacterial colonization after birth.

Highlight of 2023: The metabolic symphony - orchestrating T-cell immunity

The significance of metabolites in orchestrating immune cells is now recognized to be on par with other key immune modulators, such as cytokines or chemokines. Seminal discoveries have now been built upon with discoveries that have acted to take the discipline to new heights, particularly in T-cell immunity. This accelerated progress has uncovered a plethora of opportunities for pharmacological intervention, with the aim of harnessing immunometabolism for refined immune modulation across several pathologies. This Research Highlight focuses on the latest breakthroughs during 2023 from the preceding year that provide mechanistic insight, as well as viable translational opportunities, in the field of T-cell immunometabolism.

Abnormal energy metabolism in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a severe autoimmune disease with significant socioeconomic impact worldwide. Orderly energy metabolism is essential for normal immune function, and disordered energy metabolism is increasingly recognized as an important contributor to the pathogenesis of SLE. Disorders of energy metabolism are characterized by increased reactive oxygen species, ATP deficiency, and abnormal metabolic pathways. Oxygen and mitochondria are critical for the production of ATP, and both mitochondrial dysfunction and hypoxia affect the energy production processes. In addition, several signaling pathways, including mammalian target of rapamycin (mTOR)/adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling and the hypoxia-inducible factor (HIF) pathway also play important regulatory roles in energy metabolism. Furthermore, drugs with clear clinical effects on SLE, such as sirolimus, metformin, and tacrolimus, have been proven to improve the disordered energy metabolism of immune cells, suggesting the potential of targeting energy metabolism for the treatment of SLE. Moreover, several metabolic modulators under investigation are expected to have potential therapeutic effects in SLE. This review aimed to gain insights into the role and mechanism of abnormal energy metabolism in the pathogenesis of SLE, and summarizes the progression of metabolic modulator in the treatment of SLE.

Iron Is Critical for Mucosal-Associated Invariant T Cell Metabolism and Effector Functions

Mucosal-Associated Invariant T (MAIT) cells are a population of innate T cells that play a critical role in host protection against bacterial and viral pathogens. Upon activation, MAIT cells can rapidly respond via both TCR-dependent and -independent mechanisms, resulting in robust cytokine production. The metabolic and nutritional requirements for optimal MAIT cell effector responses are still emerging. Iron is an important micronutrient and is essential for cellular fitness, in particular cellular metabolism. Iron is also critical for many pathogenic microbes, including those that activate MAIT cells. However, iron has not been investigated with respect to MAIT cell metabolic or functional responses. In this study, we show that human MAIT cells require exogenous iron, transported via CD71 for optimal metabolic activity in MAIT cells, including their production of ATP. We demonstrate that restricting iron availability by either chelating environmental iron or blocking CD71 on MAIT cells results in impaired cytokine production and proliferation. These data collectively highlight the importance of a CD71-iron axis for human MAIT cell metabolism and functionality, an axis that may have implications in conditions where iron availability is limited.

Redox Pathogenesis in Rheumatic Diseases

Despite being some of the most anecdotally well-known roads to pathogenesis, the mechanisms governing autoimmune rheumatic diseases are not yet fully understood. The overactivation of the cellular immune system and the characteristic development of autoantibodies have been linked to oxidative stress. Typical clinical manifestations, such as joint swelling and deformities and inflammation of the skin and internal organs, have also been connected directly or indirectly to redox mechanisms. The differences in generation and restraint of oxidative stress provide compelling evidence for the broad variety in pathology among rheumatic diseases and explain some of the common triggers and discordant manifestations in these diseases. Growing evidence of redox mechanisms in pathogenesis has provided a broad array of new potential therapeutic targets. Here, we explore the mechanisms by which oxidative stress is generated, explore its roles in autoimmunity and end-organ damage, and discuss how individual rheumatic diseases exhibit unique features that offer targets for therapeutic interventions.

Dysregulated serum lipid profile is associated with inflammation and disease activity in primary Sjögren's syndrome: a retrospective study in China

PURPOSE

To investigate the relationship between the lipid profiles of patients with primary Sjögren's syndrome (pSS) and other clinical characteristics, laboratory examination, disease activity, and inflammatory factors. In addition, the risk factors for hyperlipidemia-related complications of pSS and the effect of hydroxychloroquine (HCQ) usage on the lipid profile were incorporated into this study.

METHODS

This is a single-center, retrospective study that included 367 patients who were diagnosed with pSS at Tongji Hospital, School of Medicine, Tongji University, China from January 2010 to March 2022. Initially, demographic information, clinical characteristics, medication records, and complications of the patients were gathered. A case-control analysis compared the 12 systems involvement (ESSDAI domain), clinical symptoms, and laboratory tests between pSS patients with and without dyslipidemia. A simple linear regression model was employed to investigate the relationship between serum lipid profile and inflammatory factors. Logistics regression analysis was performed to assess variables for hyperlipidemia-related complications of pSS. The paired t-test was then used to evaluate the improvement in lipid profile among pSS patients.

RESULTS

48.7 % of all pSS patients had dyslipidemia, and alterations in lipid levels were related to gender, age, and smoking status but not body mass index (BMI). Dyslipidemia is more prevalent in pSS patients who exhibit heightened autoimmunity and elevated levels of inflammation. Higher concentrations of multiple highly inflammatory factors correlate with a more severe form of dyslipidemia. Non-traditional cardiovascular risk factors may contribute to hyperlipidemia-related complications of pSS, such as increased, low complement 3 (C3) and low C4. According to our study, HCQ usage may protect against lipid-related disease in pSS.

CONCLUSION

Attention should be paid to the dyslipidemia of pSS. This research aims to clarify the population portrait of pSS patients with abnormal lipid profiles and provides insights into the correlation between metabolism and inflammation in individuals with pSS and the potential role they play in the advancement of the disease. These findings provide novel avenues for further understanding the underlying mechanisms of pSS pathogenesis.

T cell activation and deficits in T regulatory cells are associated with major depressive disorder and severity of depression

Major depressive disorder (MDD) is associated with T cell activation, but no studies have examined the combined effects of T cell activation and deficits in T regulatory (Treg) cells on the severity of acute phase MDD. Using flow cytometry, we determined the percentage and median fluorescence intensity of CD69, CD71, CD40L, and HLADR-bearing CD3+, CD4+, and CD8+ cells, and cannabinoid type 1 receptor (CB1), CD152 and GARP (glycoprotein A repetitions predominant)-bearing CD25+ FoxP3 T regulatory (Treg) cells in 30 MDD patients and 20 healthy controls in unstimulated and stimulated (anti-CD3/CD28) conditions. Based on cytokine levels, we assessed M1 macrophage, T helper (Th)-1 cell, immune-inflammatory response system (IRS), T cell growth, and neurotoxicity immune profiles. We found that the immune profiles (including IRS and neurotoxicity) were significantly predicted by decreased numbers of CD152 or GARP-bearing CD25+ FoxP3 cells or CD152 and GARP expression in combination with increases in activated T cells (especially CD8+ CD40L+ percentage and expression). MDD patients showed significantly increased numbers of CD3+ CD71+, CD3+ CD40L+, CD4+ CD71+, CD4+ CD40L+, CD4+ HLADR+, and CD8+ HLADR+ T cells, increased CD3+ CD71+, CD4+ CD71+ and CD4+ HLADR+ expression, and lowered CD25+ FoxP3 expression and CD25+ FoxP+ CB1+ numbers as compared with controls. The Hamilton Depression Rating Scale score was strongly predicted (between 30 and 40% of its variance) by a lower number of CB1 or GARP-bearing Treg cells and one or more activated T cell subtypes (especially CD8+ CD40L+). In conclusion, increased T helper and cytotoxic cell activation along with decreased Treg homeostatic defenses are important parts of MDD that lead to enhanced immune responses and, as a result, neuroimmunotoxicity.

Iron controls the development of airway hyperreactivity by regulating ILC2 metabolism and effector function

Group 2 innate lymphoid cells (ILC2s) rapidly induce a type 2 inflammation in the lungs in response to allergens. Here, we focused on the role of iron, a critical nutritional trace element, on ILC2 function and asthma pathogenesis. We found that transferrin receptor 1 (TfR1) is rapidly up-regulated and functional during ILC2 activation in the lungs, and blocking transferrin uptake reduces ILC2 expansion and activation. Iron deprivation reprogrammed ILC2 metabolism, inducing a HIF-1α-driven up-regulation of glycolysis and inhibition of oxidative mitochondrial activity. Consequently, we observed that in vivo iron chelation or induction of hypoferremia reduced the development of airway hyperreactivity in experimental models of ILC2-driven allergic asthma. Human circulating ILC2s rapidly induced TfR1 during activation, whereas inhibition of iron uptake or iron deprivation reduced effector functions. Last, we found a negative relationship between circulating ILC2 TfR1 expression and airway function in cohorts of patients with asthma. Collectively, our studies define cellular iron as a critical regulator of ILC2 function.

TCF1-LEF1 co-expression identifies a multipotent progenitor cell (TH2-MPP) across human allergic diseases

Repetitive exposure to antigen in chronic infection and cancer drives T cell exhaustion, limiting adaptive immunity. In contrast, aberrant, sustained T cell responses can persist over decades in human allergic disease. To understand these divergent outcomes, we employed bioinformatic, immunophenotyping and functional approaches with human diseased tissues, identifying an abundant population of type 2 helper T (TH2) cells with co-expression of TCF7 and LEF1, and features of chronic activation. These cells, which we termed TH2-multipotent progenitors (TH2-MPP) could self-renew and differentiate into cytokine-producing effector cells, regulatory T (Treg) cells and follicular helper T (TFH) cells. Single-cell T-cell-receptor lineage tracing confirmed lineage relationships between TH2-MPP, TH2 effectors, Treg cells and TFH cells. TH2-MPP persisted despite in vivo IL-4 receptor blockade, while thymic stromal lymphopoietin (TSLP) drove selective expansion of progenitor cells and rendered them insensitive to glucocorticoid-induced apoptosis in vitro. Together, our data identify TH2-MPP as an aberrant T cell population with the potential to sustain type 2 inflammation and support the paradigm that chronic T cell responses can be coordinated over time by progenitor cells.

Immune cells in skin inflammation, wound healing, and skin cancer

Given the self-evident importance of cutaneous immunity in the maintenance of body-surface homeostasis, disturbance of the steady-state skin is inextricably intertwined with dysfunction in cutaneous immunity. It is often overlooked by people that skin, well-known as a solid physical barrier, is also a strong immunological barrier, considering the abundant presence of immune cells including lymphocytes, granulocytes, dendritic cells, and macrophages. What's more, humoral immune components including cytokines, immunoglobulins, and antimicrobial peptides are also rich in the skin. This review centers on skin inflammation (acute and chronic, infection and aseptic inflammation), wound healing, and skin cancer to elucidate the elaborate network of immune cells in skin diseases.

Iron regulates the quiescence of naive CD4 T cells by controlling mitochondria and cellular metabolism

In response to an immune challenge, naive T cells undergo a transition from a quiescent to an activated state acquiring the effector function. Concurrently, these T cells reprogram cellular metabolism, which is regulated by iron. We and others have shown that iron homeostasis controls proliferation and mitochondrial function, but the underlying mechanisms are poorly understood. Given that iron derived from heme makes up a large portion of the cellular iron pool, we investigated iron homeostasis in T cells using mice with a T cell-specific deletion of the heme exporter, FLVCR1 [referred to as knockout (KO)]. Our finding revealed that maintaining heme and iron homeostasis is essential to keep naive T cells in a quiescent state. KO naive CD4 T cells exhibited an iron-overloaded phenotype, with increased spontaneous proliferation and hyperactive mitochondria. This was evidenced by reduced IL-7R and IL-15R levels but increased CD5 and Nur77 expression. Upon activation, however, KO CD4 T cells have defects in proliferation, IL-2 production, and mitochondrial functions. Iron-overloaded CD4 T cells failed to induce mitochondrial iron and exhibited more fragmented mitochondria after activation, making them susceptible to ferroptosis. Iron overload also led to inefficient glycolysis and glutaminolysis but heightened activity in the hexosamine biosynthetic pathway. Overall, these findings highlight the essential role of iron in controlling mitochondrial function and cellular metabolism in naive CD4 T cells, critical for maintaining their quiescent state.

Functional CRISPR screens in T cells reveal new opportunities for cancer immunotherapies

T cells are fundamental components in tumour immunity and cancer immunotherapies, which have made immense strides and revolutionized cancer treatment paradigm. However, recent studies delineate the predicament of T cell dysregulation in tumour microenvironment and the compromised efficacy of cancer immunotherapies. CRISPR screens enable unbiased interrogation of gene function in T cells and have revealed functional determinators, genetic regulatory networks, and intercellular interactions in T cell life cycle, thereby providing opportunities to revamp cancer immunotherapies. In this review, we briefly described the central roles of T cells in successful cancer immunotherapies, comprehensively summarised the studies of CRISPR screens in T cells, elaborated resultant master genes that control T cell activation, proliferation, fate determination, effector function, and exhaustion, and highlighted genes (BATF, PRDM1, and TOX) and signalling cascades (JAK-STAT and NF-κB pathways) that extensively engage in multiple branches of T cell responses. In conclusion, this review bridged the gap between discovering element genes to a specific process of T cell activities and apprehending these genes in the global T cell life cycle, deepened the understanding of T cell biology in tumour immunity, and outlined CRISPR screens resources that might facilitate the development and implementation of cancer immunotherapies in the clinic.

Immmunometabolism of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a potentially fatal chronic autoimmune disease which is underlain by complex dysfunction of the innate and adaptive immune systems. Although a series of well-defined genetic and environmental factors have been implicated in disease etiology, neither the development nor the persistence of SLE is well understood. Given that several disease susceptibility genes and environmental factors interact and influence inflammatory lineage specification through metabolism, the field of immunometabolism has become a forefront of cutting edge research. Along these lines, metabolic checkpoints of pathogenesis have been identified as targets of effective therapeutic interventions in mouse models and validated in clinical trials. Ongoing studies focus on mitochondrial oxidative stress, activation of the mechanistic target of rapamycin, calcium signaling, glucose utilization, tryptophan degradation, and metabolic cross-talk between gut microbiota and the host immune system.

Ferritin heavy chain supports stability and function of the regulatory T cell lineage

Regulatory T (TREG) cells develop via a program orchestrated by the transcription factor forkhead box protein P3 (FOXP3). Maintenance of the TREG cell lineage relies on sustained FOXP3 transcription via a mechanism involving demethylation of cytosine-phosphate-guanine (CpG)-rich elements at conserved non-coding sequences (CNS) in the FOXP3 locus. This cytosine demethylation is catalyzed by the ten-eleven translocation (TET) family of dioxygenases, and it involves a redox reaction that uses iron (Fe) as an essential cofactor. Here, we establish that human and mouse TREG cells express Fe-regulatory genes, including that encoding ferritin heavy chain (FTH), at relatively high levels compared to conventional T helper cells. We show that FTH expression in TREG cells is essential for immune homeostasis. Mechanistically, FTH supports TET-catalyzed demethylation of CpG-rich sequences CNS1 and 2 in the FOXP3 locus, thereby promoting FOXP3 transcription and TREG cell stability. This process, which is essential for TREG lineage stability and function, limits the severity of autoimmune neuroinflammation and infectious diseases, and favors tumor progression. These findings suggest that the regulation of intracellular iron by FTH is a stable property of TREG cells that supports immune homeostasis and limits the pathological outcomes of immune-mediated inflammation.

Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

High-throughput CRISPR technology: a novel horizon for solid organ transplantation

Organ transplantation is the gold standard therapy for end-stage organ failure. However, the shortage of available grafts and long-term graft dysfunction remain the primary barriers to organ transplantation. Exploring approaches to solve these issues is urgent, and CRISPR/Cas9-based transcriptome editing provides one potential solution. Furthermore, combining CRISPR/Cas9-based gene editing with an ex vivo organ perfusion system would enable pre-implantation transcriptome editing of grafts. How to determine effective intervention targets becomes a new problem. Fortunately, the advent of high-throughput CRISPR screening has dramatically accelerated the effective targets. This review summarizes the current advancements, utilization, and workflow of CRISPR screening in various immune and non-immune cells. It also discusses the ongoing applications of CRISPR/Cas-based gene editing in transplantation and the prospective applications of CRISPR screening in solid organ transplantation.

Apoptosis releases hydrogen sulfide to inhibit Th17 cell differentiation

Over 50 billion cells undergo apoptosis each day in an adult human to maintain immune homeostasis. Hydrogen sulfide (H2S) is also required to safeguard the function of immune response. However, it is unknown whether apoptosis regulates H2S production. Here, we show that apoptosis-deficient MRL/lpr (B6.MRL-Faslpr/J) and Bim-/- (B6.129S1-Bcl2l11tm1.1Ast/J) mice exhibit significantly reduced H2S levels along with aberrant differentiation of Th17 cells, which can be rescued by the additional H2S. Moreover, apoptotic cells and vesicles (apoVs) express key H2S-generating enzymes and generate a significant amount of H2S, indicating that apoptotic metabolism is an important source of H2S. Mechanistically, H2S sulfhydrates selenoprotein F (Sep15) to promote signal transducer and activator of transcription 1 (STAT1) phosphorylation and suppress STAT3 phosphorylation, leading to the inhibition of Th17 cell differentiation. Taken together, this study reveals a previously unknown role of apoptosis in maintaining H2S homeostasis and the unique role of H2S in regulating Th17 cell differentiation via sulfhydration of Sep15C38.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Cellular iron governs the host response to malaria

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor (TfrcY20H/Y20H), which limits the ability of cells to internalise iron from plasma. At homeostasis TfrcY20H/Y20H mice appear healthy and are not anaemic. However, TfrcY20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that TfrcY20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected TfrcY20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4+ T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, TfrcY20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.

Multifaceted roles of mitochondrial dysfunction in diseases: from powerhouses to saboteurs

The fact that mitochondria play a crucial part in energy generation has led to the nickname "powerhouses" of the cell being applied to them. They also play a significant role in many other cellular functions, including calcium signalling, apoptosis, and the creation of vital biomolecules. As a result, cellular function and health as a whole can be significantly impacted by mitochondrial malfunction. Indeed, malignancies frequently have increased levels of mitochondrial biogenesis and quality control. Adverse selection exists for harmful mitochondrial genome mutations, even though certain malignancies include modifications in the nuclear-encoded tricarboxylic acid cycle enzymes that generate carcinogenic metabolites. Since rare human cancers with mutated mitochondrial genomes are often benign, removing mitochondrial DNA reduces carcinogenesis. Therefore, targeting mitochondria offers therapeutic options since they serve several functions and are crucial to developing malignant tumors. Here, we discuss the various steps involved in the mechanism of cancer for which mitochondria plays a significant role, as well as the role of mitochondria in diseases other than cancer. It is crucial to understand mitochondrial malfunction to target these organelles for therapeutic reasons. This highlights the significance of investigating mitochondrial dysfunction in cancer and other disease research.

Tregs in transplantation tolerance: role and therapeutic potential

CD4+ Foxp3+ regulatory T cells (Tregs) are indispensable for preventing autoimmunity, and they play a role in cancer and transplantation settings by restraining immune responses. In this review, we describe evidence for the importance of Tregs in the induction versus maintenance of transplantation tolerance, discussing insights into mechanisms of Treg control of the alloimmune response. Further, we address the therapeutic potential of Tregs as a clinical intervention after transplantation, highlighting engineered CAR-Tregs as well as expansion of donor and host Tregs.

Endosome Traffic Modulates Pro-Inflammatory Signal Transduction in CD4+ T Cells-Implications for the Pathogenesis of Systemic Lupus Erythematosus

Endocytic recycling regulates the cell surface receptor composition of the plasma membrane. The surface expression levels of the T cell receptor (TCR), in concert with signal transducing co-receptors, regulate T cell responses, such as proliferation, differentiation, and cytokine production. Altered TCR expression contributes to pro-inflammatory skewing, which is a hallmark of autoimmune diseases, such as systemic lupus erythematosus (SLE), defined by a reduced function of regulatory T cells (Tregs) and the expansion of CD4⁺ helper T (Th) cells. The ensuing secretion of inflammatory cytokines, such as interferon-γ and interleukin (IL)-4, IL-17, IL-21, and IL-23, trigger autoantibody production and tissue infiltration by cells of the adaptive and innate immune system that induce organ damage. Endocytic recycling influences immunological synapse formation by CD4⁺ T lymphocytes, signal transduction from crosslinked surface receptors through recruitment of adaptor molecules, intracellular traffic of organelles, and the generation of metabolites to support growth, cytokine production, and epigenetic control of DNA replication and gene expression in the cell nucleus. This review will delineate checkpoints of endosome traffic that can be targeted for therapeutic interventions in autoimmune and other disease conditions.

A cellular overview of immunometabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease, characterized by a breakdown of immune tolerance and the development of autoantibodies against nucleic self-antigens. Immunometabolism is a rapidly expanding scientific field investigating the metabolic programming of cells of the immune system. During the normal immune response, extensive reprogramming of cellular metabolism occurs, both to generate adenosine triphosphate and facilitate protein synthesis, and also to manage cellular stress. Major pathways upregulated include glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle and the pentose phosphate pathway, among others. Metabolic reprogramming also occurs to aid resolution of inflammation. Immune cells of both patients with SLE and lupus-prone mice are characterized by metabolic abnormalities resulting in an altered functional and inflammatory state. Recent studies have described how metabolic reprogramming occurs in many cell populations in SLE, particularly CD4+ T cells, e.g. favouring a glycolytic profile by overactivation of the mechanistic target of rapamycin pathway. These advances have led to an increased understanding of the metabolic changes affecting the inflammatory profile of T and B cells, monocytes, dendritic cells and neutrophils, and how they contribute to autoimmunity and SLE pathogenesis. In the current review, we aim to summarize recent advances in the field of immunometabolism involved in SLE and how these could potentially lead to new therapeutic strategies in the future.