NKT cell subsets as key participants in liver physiology and pathology

IL-2-mediated hepatotoxicity: knowledge gap identification based on the irAOP concept

Drug-induced hepatotoxicity constitutes a major reason for non-approval and post-marketing withdrawal of pharmaceuticals. In many cases, preclinical models lack predictive capacity for hepatic damage in humans. A vital concern is the integration of immune system effects in preclinical safety assessment. The immune-related Adverse Outcome Pathway (irAOP) approach, which is applied within the Immune Safety Avatar (imSAVAR) consortium, presents a novel method to understand and predict immune-mediated adverse events elicited by pharmaceuticals and thus targets this issue. It aims to dissect the molecular mechanisms involved and identify key players in drug-induced side effects. As irAOPs are still in their infancy, there is a need for a model irAOP to validate the suitability of this tool. For this purpose, we developed a hepatotoxicity-based model irAOP for recombinant human IL-2 (aldesleukin). Besides producing durable therapeutic responses against renal cell carcinoma and metastatic melanoma, the boosted immune activation upon IL-2 treatment elicits liver damage. The availability of extensive data regarding IL-2 allows both the generation of a comprehensive putative irAOP and to validate the predictability of the irAOP with clinical data. Moreover, IL-2, as one of the first cancer immunotherapeutics on the market, is a blueprint for various biological and novel treatment regimens that are under investigation today. This review provides a guideline for further irAOP-directed research in immune-mediated hepatotoxicity.

Innate-like T cells in liver disease

Mammalian innate-like T cells (ILTCs), including mucosal-associated invariant T (MAIT), natural killer T (NKT), and γδ T cells, are abundant tissue-resident lymphocytes that have recently emerged as orchestrators of hepatic inflammation, tissue repair, and immune homeostasis. This review explores the involvement of different ILTC subsets in liver diseases. We explore the mechanisms underlying the pro- and anti-inflammatory effector functions of ILTCs in a context-dependent manner. We highlight latest findings regarding the dynamic interplay between ILTC functional subsets and other immune and parenchymal cells which may inform candidate immunomodulatory strategies to achieve improved clinical outcomes in liver diseases. We present new insights into how distinct gene expression programs in hepatic ILTCs are induced, maintained, and reprogrammed in a context- and disease stage-dependent manner.

Soluble CD46 as a diagnostic marker of hepatic steatosis

BACKGROUND

The increasing prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) incurs substantial morbidity, mortality and healthcare costs. Detection and clinical intervention at early stages of disease improves prognosis; however, we are currently limited by a lack of reliable diagnostic tests for population screening and monitoring responses to therapy. To address this unmet need, we investigated human invariant Natural Killer T cell (iNKT) activation by fat-loaded hepatocytes, leading to the discovery that circulating soluble CD46 (sCD46) levels accurately predict hepatic steatosis.

METHODS

sCD46 in plasma was measured using a newly developed immuno-competition assay in two independent cohorts: Prospective living liver donors (n = 156; male = 66, female = 90) and patients with liver tumours (n = 91; male = 58, female = 33). sCD46 levels were statistically evaluated as a predictor of hepatic steatosis.

FINDINGS

Interleukin-4-secreting (IL-4+) iNKT cells were over-represented amongst intrahepatic lymphocytes isolated from resected human liver samples. IL-4+ iNKT cells preferentially developed in cocultures with a fat-loaded, hepatocyte-like cell line, HepaRG. This was attributed to induction of matrix metalloproteases (MMP) in fat-loaded HepaRG cells and primary human liver organoids, which led to indiscriminate cleavage of immune receptors. Loss of cell-surface CD46 resulted in unrepressed differentiation of IL-4+ iNKT cells. sCD46 levels were elevated in patients with hepatic steatosis. Discriminatory cut-off values for plasma sCD46 were found that accurately classified patients according to histological steatosis grade.

INTERPRETATION

sCD46 is a reliable clinical marker of hepatic steatosis, which can be conveniently and non-invasively measured in serum and plasma samples, raising the possibility of using sCD46 levels as a diagnostic method for detecting or grading hepatic steatosis.

FUNDING

F.B. was supported by the Else Kröner Foundation (Award 2016_kolleg.14). G.G. was supported by the Bristol Myers Squibb Foundation for Immuno-Oncology (Award FA-19-009). N.S. was supported by a Wellcome Trust Fellowship (211113/A/18/Z). J.A.H. received funding from the European Union's Horizon 2020 research and innovation programme (Award 860003). J.M.W. received funding from the Else Kröner Foundation (Award 2015_A10).

CCR2+TREM-1+ monocytes promote natural killer T cell dysfunction contributing towards HBV disease progression

Natural killer T (NKT) cells are amongst the most important innate immune cells against hepatitis B virus (HBV) infection. Moreover, previous studies have shown that HBV infection induced TREM-1+ expression in monocyte and secretion of inflammatory cytokines. Thus, this prompted us to elucidate the role of TREM-1+ monocytes in regulating the function of iNKT cells. Ninety patients and 20 healthy participants were enrolled in the study. The percentage and phenotype of iNKT cells and TREM-1+ monocytes were measured in the peripheral blood of healthy controls (HC), patients with chronic HBV infection (CHB), HBV-related liver cirrhosis (LC), and HBV-related acute-on-chronic liver failure (ACLF) via flow cytometry. Moreover, co-culture experiments with iNKT cells and TREM-1 overexpressing THP-1 cells were performed to determine the role of TREM-1 in the regulation of NKT cell function. We observed that the percentage of iNKT cells and CD4-iNKT cells gradually decreased, whereas the percentage of CCR2+TREM-1+ monocytes increased with the progression of the disease. In addition, activation of the TREM-1 signaling pathway induced the secretion of inflammatory cytokines leading to pyroptosis of iNKT cells and secretion of IL-17 contributing towards disease progression. Therefore, this study suggests that blocking the activation of TREM-1 in monocytes could promote the elimination of HBV by inhibiting pyroptosis of iNKT cells and restoring their function. However, further studies are required to validate these results that would help in developing new treatment strategies for patients with HBV infections.

Role of sulfatide-reactive vNKT cells in promoting lung Treg cells via dendritic cell modulation in asthma models

Our previous studies have showed that sulfatide-reactive type II NKT (i.e. variant NKT, vNKT) cells inhibit the immunogenic maturation during the development of mature lung dendritic cells (LDCs), leading todeclined allergic airway inflammation in asthma. Nonetheless, the specific immunoregulatory roles of vNKT cells in LDC-mediated Th2 cell responses remain incompletely understood. Herein, we found that administration of sulfatide facilitated the generation of CD4+FoxP3+ regulatory T (Treg) cells in the lungs of wild-type mice, but not in CD1d-/- and Jα18-/- mice, after ovalbumin or house dust mite exposure. This finding implies that the enhancement of lung Treg cells by sulfatide requires vNKT cells, which dependent on invariant NKT (iNKT) cells. Furthermore, the CD4+FoxP3+ Treg cells induced by sulfatide-reactive vNKT cells were found to be associated with PD-L1 molecules expressed on LDCs, and this association was dependent on iNKT cells. Collectively, our findings suggest that in asthma-mimicking murine models, sulfatide-reactive vNKT cells facilitate the generation of lung Treg cells through inducing tolerogenic properties in LDCs, and this process is dependent on the presence of lung iNKT cells. These results may provide a potential therapeutic approach to treat allergic asthma.

SIRT3: A potential therapeutic target for liver fibrosis

Sirtuin3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase located in the mitochondria, which mainly regulates the acetylation of mitochondrial proteins. In addition, SIRT3 is involved in critical biological processes, including oxidative stress, inflammation, DNA damage, and apoptosis, all of which are closely related to the progression of liver disease. Liver fibrosis characterized by the deposition of extracellular matrix is a result of long termed or repeated liver damage, frequently accompanied by damaged hepatocytes, the recruitment of inflammatory cells, and the activation of hepatic stellate cells. Based on the functions and pharmacology of SIRT3, we will review its roles in liver fibrosis from three aspects: First, the main functions and pharmacological effects of SIRT3 were investigated based on its structure. Second, the roles of SIRT3 in major cells in the liver were summarized to reveal its mechanism in developing liver fibrosis. Last, drugs that regulate SIRT3 to prevent and treat liver fibrosis were discussed. In conclusion, exploring the pharmacological effects of SIRT3, especially in the liver, may be a potential strategy for treating liver fibrosis.

Enhancing NKT cell-mediated immunity against hepatocellular carcinoma: Role of XYXD in promoting primary bile acid synthesis and improving gut microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

'Xiayuxue decoction' (XYXD) is a traditional Chinese medicine compound, composing of three natural medicines: Rheum officinale Baill., Prunus persica (L.) Batsch and Eupolyphaga sinensis Walker. It is derived from the famous traditional Chinese medical classics 'Jingui Yaolue' and has been used for thousands of years. In the Guidelines for the Diagnosis and Treatment of Primary liver Cancer issued by China's Health Commission, XYXD was applied in the treatment of primary liver cancer.

AIM OF THE STUDY

To clarify the pharmacodynamic material basis and mechanism of XYXD in the treatment of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Firstly, the active components of XYXD and its distribution in vivo were identified by Ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Then, the effective components and mechanism of XYXD against HCC were explored by network pharmacology combined with cell experiments in vitro. Furthermore, the anti-HCC effect of XYXD was determined by animal experiments in vivo. Metagenomic sequencing was used to detect its effect in gut microbiota, and targeted metabolism was used to detect the changes of bile acids in the liver. Finally, the related targets of NKT cell immune function activation were detected by RT-qPCR and Elisa.

RESULTS

A total of 113 active ingredients in XYXD were identified, and the distribution of active ingredients in blood, liver, tumor, cecum, intestinal contents and feces was clarified. The circulation process and active ingredient group of XYXD were preliminarily clarified. In addition, we found five anti-HCC active ingredients in XYXD through network pharmacology combined with cell experiments in vitro, among which aloe emodin had the most significant effect, and predicted the potential mechanism of XYXD against HCC through NKT cell pathway. Moreover, the inhibitory effect of XYXD on liver tumor growth was clarified by animal experiments in vivo. The mechanism was mainly to promote the production of bile salt hydrolase (BSH) by increasing the abundance of Bacteroides and Lactobacillus, BSH converts conjugated bile acids into primary bile acids, and reduces the conversion of primary bile acids to secondary bile acids by reducing the abundance of Eubacterium, thereby increasing the content of primary bile acids. Primary bile acids trigger NKT cells in the liver to produce interferon-γ to exert anti-HCC immune effects.

CONCLUSION

This study found that the traditional Chinese herbal formula XYXD can trigger the immune effect of NKT cells against HCC by regulating the interaction between gut microbiota and bile acids.

Lipid metabolism in the immune niche of tumor-prone liver microenvironment

The liver is a common primary site not only for tumorigenesis, but also for cancer metastasis. Advanced cancer patients with liver metastases also show reduced response rates and survival benefits when treated with immune checkpoint inhibitors. Accumulating evidence has highlighted the importance of the liver immune microenvironment in determining tumorigenesis, metastasis-organotropism, and immunotherapy resistance. Various immune cells such as T cells, natural killer and natural killer T cells, macrophages and dendritic cells, and stromal cells including liver sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells, and hepatocytes are implicated in contributing to the immune niche of tumor-prone liver microenvironment. In parallel, as the major organ for lipid metabolism, the increased abundance of lipids and their metabolites is linked to processes crucial for nonalcoholic fatty liver disease and related liver cancer development. Furthermore, the proliferation, differentiation, and functions of hepatic immune and stromal cells are also reported to be regulated by lipid metabolism. Therefore, targeting lipid metabolism may hold great potential to reprogram the immunosuppressive liver microenvironment and synergistically enhance the immunotherapy efficacy in the circumstance of liver metastasis. In this review, we describe how the hepatic microenvironment adapts to the lipid metabolic alterations in pathologic conditions like nonalcoholic fatty liver disease. We also illustrate how these immunometabolic alterations promote the development of liver cancers and immunotherapy resistance. Finally, we discuss the current therapeutic options and hypothetic combination immunotherapies for the treatment of advanced liver cancers.

The role of natural killer T cells in liver transplantation

Natural killer T cells (NKTs) are innate-like lymphocytes that are abundant in the liver and participate in liver immunity. NKT cells express both NK cell and T cell markers, modulate innate and adaptive immune responses. Type I and Type II NKT cells are classified according to the TCR usage, while they recognize lipid antigen in a non-classical major histocompatibility (MHC) molecule CD1d-restricted manner. Once activated, NKT cells can quickly produce cytokines and chemokines to negatively or positively regulate the immune responses, depending on the different NKT subsets. In liver transplantation (LTx), the immune reactions in a series of processes determine the recipients' long-term survival, including ischemia-reperfusion injury, alloresponse, and post-transplant infection. This review provides insight into the research on NKT cells subpopulations in LTx immunity during different processes, and discusses the shortcomings of the current research on NKT cells. Additionally, the CD56-expressing T cells are recognized as a NK-like T cell population, they were also discussed during these processes.

Natural Killer T (NKT) Cells in Autoimmune Hepatitis: Current Evidence from Basic and Clinical Research

Natural killer T (NKT) cells are unconventional T cells that are activated by glycolipid antigens. They can produce a variety of inflammatory and regulatory cytokines and, therefore, modulate multiple aspects of the immune response in different pathological settings, including autoimmunity. NKT cells have also been implicated in the immunopathogenesis of autoimmune hepatitis, and in this review we summarize and analyze the main studies investigating the involvement and/or homeostasis of NKT cells in this disease. In detail, the evidence from both basic and clinical research has been specifically analyzed. Even though the experimental murine models supported a relevant role of NKT cells in immune-mediated hepatic injury, very few studies specifically investigated NKT cell homeostasis in patients with autoimmune hepatitis; however, these initial studies reported some alterations of NKT cells in these patients, which may also correlate with the disease activity to some extent. Further clinical studies are needed to investigate the potential role and use of NKT cell analysis as a disease marker of clinical relevance, and to better understand the precise cellular and molecular mechanisms by which NKT cells contribute to the pathogenesis of autoimmune hepatitis.

Natural Killer T Cell Diversity and Immunotherapy

Invariant natural killer T cells (iNKTs), a type of unconventional T cells, share features with NK cells and have an invariant T cell receptor (TCR), which recognizes lipid antigens loaded on CD1d molecules, a major histocompatibility complex class I (MHC-I)-like protein. This interaction produces the secretion of a wide array of cytokines by these cells, including interferon gamma (IFN-γ) and interleukin 4 (IL-4), allowing iNKTs to link innate with adaptive responses. Interestingly, molecules that bind CD1d have been identified that enable the modulation of these cells, highlighting their potential pro-inflammatory and immunosuppressive capacities, as required in different clinical settings. In this review, we summarize key features of iNKTs and current understandings of modulatory α-galactosylceramide (α-GalCer) variants, a model iNKT cell activator that can shift the outcome of adaptive immune responses. Furthermore, we discuss advances in the development of strategies that modulate these cells to target pathologies that are considerable healthcare burdens. Finally, we recapitulate findings supporting a role for iNKTs in infectious diseases and tumor immunotherapy.

Tumor Immune Microenvironment as a New Therapeutic Target for Hepatocellular Carcinoma Development

Development of hepatocellular carcinoma (HCC) is driven by a multistep and long-term process. Because current therapeutic strategies are limited for HCC patients, there are increasing demands for understanding of immunotherapy, which has made technological and conceptual innovations in the treatment of cancer. Here, I discuss HCC immunotherapy in the view of interaction between liver resident cells and immune cells.

Sex-based differences in natural killer T cell-mediated protection against diet-induced steatohepatitis in Balb/c mice

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is prevalent in Western countries, evolving into metabolic dysfunction-associated steatohepatitis (MASH) with a sexual dimorphism. Fertile women exhibit lower MASLD risk than men, which diminishes post-menopause. While NKT-cell involvement in steatohepatitis is debated, discrepancies may stem from varied mouse strains used, predominantly C57BL6/J with Th1-dominant responses. Exploration of steatohepatitis, encompassing both genders, using Balb/c background, with Th2-dominant immune response, and CD1d-deficient mice in the Balb/c background (lacking Type I and Type II NKT cells) can clarify gender disparities and NKT-cell influence on MASH progression.

METHODS

A high fat and choline-deficient (HFCD) diet was used in male and female mice, Balb/c mice or CD1d-/- mice in the Balb/c background that exhibit a Th2-dominant immune response. Liver fibrosis and inflammatory gene expression were measured by qPCR, and histology assessment. NKT cells, T cells, macrophages and neutrophils were assessed by flow cytometry.

RESULTS

Female mice displayed milder steatohepatitis after 6 weeks of HFCD, showing reduced liver damage, inflammation, and fibrosis compared to males. Male Balb/c mice exhibited NKT-cell protection against steatohepatitis whereas CD1d-/- males on HFCD presented decreased hepatoprotection, increased liver fibrosis, inflammation, neutrophilic infiltration, and inflammatory macrophages. In contrast, the NKT-cell role was negligible in early steatohepatitis development in both female mice, as fibrosis and inflammation were similar despite augmented liver damage in CD1d-/- females. Relevant, hepatic type I NKT levels in female Balb/c mice were significantly lower than in male.

CONCLUSIONS

NKT cells exert a protective role against experimental steatohepatitis as HFCD-treated CD1d-/- males had more severe fibrosis and inflammation than male Balb/c mice. In females, the HFCD-induced hepatocellular damage and the immune response are less affected by NKT cells on early steatohepatitis progression, underscoring sex-specific NKT-cell influence in MASH development.

CD1d-dependent neuroinflammation impairs tissue repair and functional recovery following a spinal cord injury

Tissue damage resulting from a spinal cord injury (SCI) is primarily driven by a robust neuroimmune/neuroinflammatory response. This intricate process is mainly governed by a multitude of cytokines and cell surface proteins in the central nervous system (CNS). However, the critical components of the neuroimmune/neuroinflammatory response during SCI are still not well-defined. In this study, we investigated the impact of CD1d, an MHC class I-like molecule mostly known for presenting lipid antigens to natural killer T (NKT) cells and regulating immune/inflammatory responses, on neuroimmune/neuroinflammatory responses induced by SCI. We observed an increased expression of CD1d on various cell types within the spinal cord, including microglia/macrophages, oligodendrocytes (ODCs), and endothelial cells (DCs), but not on neurons or astrocytes post-SCI. In comparison to wildtype (WT) mice, a T10 contusive SCI in CD1d knockout (CD1dKO or Cd1d -/- ) mice resulted in markedly reduced proinflammatory cytokine release, microglia/macrophage activation and proliferation. Following SCI, the levels of inflammatory cytokines and activation/proliferation of microglia/macrophages were dramatically reduced, while anti-inflammatory cytokines such as IL-4 and growth factors like VEGF were substantially increased in the spinal cord tissues of CD1dKO mice when compared to WT mice. In the post-acute phase of SCI (day 7 post-SCI), CD1dKO mice had a significantly higher frequency of tissue-repairing macrophages, but not other types of immune cells, in the injured spinal cord tissues compared to WT mice. Moreover, CD1d-deficiency protected spinal cord neuronal cells and tissue, promoting functional recovery after a SCI. However, the neuroinflammation in WT mouse spinal cords was independent of the canonical CD1d/NKT cell axis. Finally, treatment of injured mice with a CD1d-specific monoclonal antibody significantly enhanced neuroprotection and improved functional recovery. Therefore, CD1d promotes the proinflammatory response following a SCI and represents a potential therapeutic target for spinal cord repair.

Significance Statement

The cell surface molecule, CD1d, is known to be recognized by cells of the immune system. To our knowledge, this is the first observation that the CD1d molecule significantly contributes to neuroinflammation following a spinal cord injury (SCI) in a manner independent of the CD1d/NKT cell axis. This is important, because this work reveals CD1d as a potential therapeutic target following an acute SCI for which there are currently no effective treatments.

Emerging roles of plasmacytoid dendritic cell crosstalk in tumor immunity

Plasmacytoid dendritic cells (pDCs) are a pioneer cell type that produces type I interferon (IFN-I) and promotes antiviral immune responses. However, they are tolerogenic and, when recruited to the tumor microenvironment (TME), play complex roles that have long been a research focus. The interactions between pDCs and other components of the TME, whether direct or indirect, can either promote or hinder tumor development; consequently, pDCs are an intriguing target for therapeutic intervention. This review provides a comprehensive overview of pDC crosstalk in the TME, including crosstalk with various cell types, biochemical factors, and microorganisms. An in-depth understanding of pDC crosstalk in TME should facilitate the development of novel pDC-based therapeutic methods.

Tissue-resident and innate-like T cells in patients with advanced chronic liver disease

Chronic liver disease results from the orchestrated interplay of components of innate and adaptive immunity in response to liver tissue damage. Recruitment, positioning, and activation of immune cells can contribute to hepatic cell death, inflammation, and fibrogenesis. With disease progression and increasing portal pressure, repeated translocation of bacterial components from the intestinal lumen through the epithelial and vascular barriers leads to persistent mucosal, hepatic, and systemic inflammation which contributes to tissue damage, immune dysfunction, and microbial infection. It is increasingly recognised that innate-like and adaptive T-cell subsets located in the liver, mucosal surfaces, and body cavities play a critical role in the progression of advanced liver disease and inflammatory complications of cirrhosis. Mucosal-associated invariant T cells, natural killer T cells, γδ T cells, and tissue-resident memory T cells in the gut, liver, and ascitic fluid share certain characteristic features, which include that they recognise microbial products, tissue alarmins, cytokines, and stress ligands in tissues, and perform effector functions in chronic liver disease. This review highlights recent advances in the comprehension of human tissue-resident and unconventional T-cell populations and discusses the mechanisms by which they contribute to inflammation, fibrosis, immunosuppression, and antimicrobial surveillance in patients with cirrhosis. Understanding the complex interactions of immune cells in different compartments and their contribution to disease progression will provide further insights for effective diagnostic interventions and novel immunomodulatory strategies in patients with advanced chronic liver disease.

Immune landscape and immunotherapy of hepatocellular carcinoma: focus on innate and adaptive immune cells

Hepatocellular carcinoma (HCC) is responsible for roughly 90% of all cases of primary liver cancer, and the cases are on the rise. The treatment of advanced HCC is a serious challenge. Immune checkpoint inhibitor (ICI) therapy has marked a watershed moment in the history of HCC systemic treatment. Atezolizumab in combination with bevacizumab has been approved as a first-line treatment for advanced HCC since 2020; however, the combination therapy is only effective in a limited percentage of patients. Considering that the tumor immune microenvironment (TIME) has a great impact on immunotherapies for HCC, an in-depth understanding of the immune landscape in tumors and the current immunotherapeutic approaches is extremely necessary. We elaborate on the features, functions, and cross talk of the innate and adaptive immune cells in HCC and highlight the benefits and drawbacks of various immunotherapies for advanced HCC, as well as future projections. HCC consists of a heterogeneous group of cancers with distinct etiologies and immune microenvironments. Almost all the components of innate and adaptive immune cells in HCC have altered, showing a decreasing trend in the number of tumor suppressor cells and an increasing trend in the pro-cancer cells, and there is also cross talk between various cell types. Various immunotherapies for HCC have also shown promising efficacy and application prospect. There are multilayered interwoven webs among various immune cell types in HCC, and emerging evidence demonstrates the promising prospect of immunotherapeutic approaches for HCC.

Updates on the Immune Cell Basis of Hepatic Ischemia-Reperfusion Injury

Liver ischemia-reperfusion injury (IRI) is the main cause of organ dysfunction and failure after liver surgeries including organ transplantation. The mechanism of liver IRI is complex and numerous signals are involved but cellular metabolic disturbances, oxidative stress, and inflammation are considered the major contributors to liver IRI. In addition, the activation of inflammatory signals exacerbates liver IRI by recruiting macrophages, dendritic cells, and neutrophils, and activating NK cells, NKT cells, and cytotoxic T cells. Technological advances enable us to understand the role of specific immune cells during liver IRI. Accordingly, therapeutic strategies to prevent or treat liver IRI have been proposed but no definitive and effective therapies exist yet. This review summarizes the current update on the immune cell functions and discusses therapeutic potentials in liver IRI. A better understanding of this complex and highly dynamic process may allow for the development of innovative therapeutic approaches and optimize patient outcomes.

Type 1 invariant natural killer T cells in chronic inflammation and tissue fibrosis

Chronic tissue inflammation often results in fibrosis characterized by the accumulation of extracellular matrix components remodeling normal tissue architecture and function. Recent studies have suggested common immune mechanisms despite the complexity of the interactions between tissue-specific fibroblasts, macrophages, and distinct immune cell populations that mediate fibrosis in various tissues. Natural killer T (NKT) cells recognizing lipid antigens bound to CD1d molecules have been shown to play an important role in chronic inflammation and fibrosis. Here we review recent data in both experimental models and in humans that suggest a key role of type 1 invariant NKT (iNKT) cell activation in the progression of inflammatory cascades leading to recruitment of neutrophils and activation of the inflammasome, macrophages, fibroblasts, and, ultimately, fibrosis. Emerging evidence suggests that iNKT-associated mechanisms contribute to type 1, type 2 and type 3 immune pathways mediating tissue fibrosis, including idiopathic pulmonary fibrosis (IPF). Thus, targeting a pathway upstream of these immune mechanisms, such as the inhibition of iNKT activation, may be important in modulating various fibrotic conditions.

A Personalized Cancer Vaccine that Induces Synergistic Innate and Adaptive Immune Responses

To demonstrate potent efficacy, a cancer vaccine needs to activate both innate and adaptive immune cells. Personalized cancer vaccine strategies often require the identification of patient-specific neoantigens; however, the clonal and mutational heterogeneity of cancer cells presents inherent challenges. Here, extracellular nanovesicles derived from alpha-galactosylceramide-conjugated autologous acute myeloid leukemia (AML) cells (ECNV-αGC) are presented as a personalized therapeutic vaccine that activates both innate and adaptive immune responses, bypassing the need to identify patient-specific neoantigens. ECNV-αGC vaccination directly engages with and activates both invariant natural killer T (iNKT) cells and leukemia-specific CD8+ T cells in mice with AML, thereby promoting long-term anti-leukemic immune memory. ECNV-αGC sufficiently serves as an antigen-presenting platform that can directly activate antigen-specific CD8+ T cells even in the absence of dendritic cells, thereby demonstrating a multifaceted cellular mechanism of immune activation. Moreover, ECNV-αGC vaccination results in a significantly lower AML burden and higher percentage of leukemia-free survivors among cytarabine-treated hosts with AML. Human AML-derived ECNV-αGCs activate iNKT cells in both healthy individuals and patients with AML regardless of responsiveness to conventional therapies. Together, autologous AML-derived ECNV-αGCs may be a promising personalized therapeutic vaccine that efficiently establishes AML-specific long-term immunity without requiring the identification of neoantigens.

Early activation and recruitment of invariant natural killer T cells during liver ischemia-reperfusion: the major role of the alarmin interleukin-33

Over the past thirty years, the complexity of the αβ-T cell compartment has been enriched by the identification of innate-like T cells (ITCs), which are composed mainly of invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells. Based on animal studies using ischemia-reperfusion (IR) models, a key role has been attributed to iNKT cells in close connection with the alarmin/cytokine interleukin (IL)-33, as early sensors of cell-stress in the initiation of acute sterile inflammation. Here we have investigated whether the new concept of a biological axis of circulating iNKT cells and IL-33 applies to humans, and may be extended to other ITC subsets, namely MAIT and γδ-T cells, in the acute sterile inflammation sequence occurring during liver transplant (LT). From a prospective biological collection of recipients, we reported that LT was accompanied by an early and preferential activation of iNKT cells, as attested by almost 40% of cells having acquired the expression of CD69 at the end of LT (i.e. 1-3 hours after portal reperfusion), as opposed to only 3-4% of conventional T cells. Early activation of iNKT cells was positively correlated with the systemic release of the alarmin IL-33 at graft reperfusion. Moreover, in a mouse model of hepatic IR, iNKT cells were activated in the periphery (spleen), and recruited in the liver in WT mice, as early as the first hour after reperfusion, whereas this phenomenon was virtually missing in IL-33-deficient mice. Although to a lesser degree than iNKT cells, MAIT and γδ-T cells also seemed targeted during LT, as attested by 30% and 10% of them acquiring CD69 expression, respectively. Like iNKT cells, and in clear contrast to γδ-T cells, activation of MAIT cells during LT was closely associated with both release of IL-33 immediately after graft reperfusion and severity of liver dysfunction occurring during the first three post-operative days. All in all, this study identifies iNKT and MAIT cells in connection with IL-33 as new key cellular factors and mechanisms of acute sterile inflammation in humans. Further investigations are required to confirm the implication of MAIT and iNKT cell subsets, and to precisely assess their functions, in the clinical course of sterile inflammation accompanying LT.

Insights into the impact of hepatitis B virus on hepatic stellate cell activation

During chronic hepatitis B virus (HBV) infection, hepatic fibrosis is a serious pathological condition caused by virus-induced liver damage. The activation of hepatic stellate cells (HSCs) is a central event in the occurrence and progression of liver fibrosis. Although accumulating evidence has shown that HBV directly stimulates HSC activation, whether the virus infects and replicates in HSCs remains controversial. Inflammation is one of the obvious characteristics of chronic HBV infection, and it has been demonstrated that persistent inflammation has a predominant role in triggering and maintaining liver fibrosis. In particular, the regulation of HSC activation by HBV-related hepatocytes via various inflammatory modulators, including TGF-β and CTGF, in a paracrine manner has been reported. In addition to these inflammation-related molecules, several inflammatory cells are essential for the progression of HBV-associated liver fibrosis. Monocytes, macrophages, Th17 cells, NK cells, as well as NKT cells, participate in the modulation of HBV-related liver fibrosis by interacting with HSCs. This review summarizes current findings on the effects of HBV and the relevant molecular mechanisms involved in HSC activation. Because HSC activation is essential for liver fibrosis, targeting HSCs is an attractive therapeutic strategy to prevent and reverse hepatic fibrosis induced by HBV infection. Video abstract.

ILC1: Development, maturation, and transcriptional regulation

Type 1 Innate Lymphoid cells (ILC1s) are tissue-resident cells that partake in the regulation of inflammation and homeostasis. A major feature of ILC1s is their ability to rapidly respond after infections. The effector repertoire of ILC1s includes the pro-inflammatory cytokines IFN-γ and TNF-α and cytotoxic mediators such as granzymes, which enable ILC1s to establish immune responses and to directly kill target cells. Recent advances in the characterization of ILC1s have considerably furthered our understanding of ILC1 development and maintenance in tissues. In particular, it has become clear how ILC1s operate independently from conventional natural killer cells, with which they share many characteristics. In this review, we discuss recent developments with regards to the differentiation, polarization, and effector maturation of ILC1s. These processes may underlie the observed heterogeneity in ILC1 populations within and between different tissues. Next, we highlight transcriptional programs that control each of the separate steps in the differentiation of ILC1s. These transcriptional programs are shared with other tissue-resident type-1 lymphocytes, such as tissue-resident memory T cells (T_RM ) and invariant natural killer T cells (iNKT), highlighting that ILC1s utilize networks of transcriptional regulation that are conserved between lymphocyte lineages to respond effectively to tissue-invading pathogens.

Capsaicin shapes gut microbiota and pre-metastatic niche to facilitate cancer metastasis to liver

Dietary factors are fundamental in tumorigenesis throughout our lifetime. A spicy diet has been ambiguous on the development of cancers, especially in the study of colon cancer metastasis. Here, we utilized a mouse metastasis model to test the potential role of capsaicin in influencing metastasis. Long-term continuous administration of capsaicin diet (300 mg/kg) to mice promotes the formation of liver pre-metastatic niche to facilitate the metastasis of colon cancer cells. Bacteria translocation to liver is clearly observed. Capsaicin increases intestinal barrier permeability and disrupts gut vascular barrier by altering the composition of gut microbiota. Capsaicin not only changes the abundance of mucin-related bacteria like Akkermanisa and Muribaculaceae, but also bacteria involved in bile acids metabolism. Dysregulated bile acids profile is related to the recruitment of natural killer T (NKT) cells in pre-metastatic niche, primary bile acid α-Muricholic acid can enhance the recruitment of NKT cells, while secondary bile acids Glycoursodeoxycholic acid and Taurohyodeoxycholic acid impair the recruitment of NKT cells. These findings reveal long term consumption of capsaicin increases the risk of cancer metastasis through modulating the gut microbiota. Capsaicin (300 mg/kg) disrupts gut barrier and promotes the translocation of bacteria to liver, while altered bile acids metabolism affects the recruitment of NKT cells in liver, forming a pre-metastatic niche and promoting cancer metastasis.

Obeticholic acid and 5β-cholanic acid 3 exhibit anti-tumor effects on liver cancer through CXCL16/CXCR6 pathway

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy with a high incidence and mortality rate. Previous in vitro and in vivo studies have confirmed that liver sinusoidal endothelial cells (LSEC) secrete CXCL16, which acts as a messenger to increase the hepatic accumulation of CXCR6⁺ natural killer T (NKT) cells and exert potent antitumor effects. However, evidence for this process in humans is lacking and its clinical significance is still unclear. In this study, by dissecting the human HCC single-cell RNA-seq data, we verified this process through cellphoneDB. NKT cells in patients with high expression of CXCL16 exhibited a higher activation state and produced more interferon-γ (IFN-γ) compared with those with low expression. We next investigated the signaling pathways between activated (CD69 high) and unactivated NKT cells (CD69 low) using NKT cell-developmental trajectories and functional enrichment analyses. In vivo experiments, we found that farnesoid X receptor agonist (obeticholic acid) combined with the takeda G protein coupled receptor 5 antagonist (5β-cholanic acid 3) exhibited significant tumor suppressive effects in the orthotopic liver tumor model and this result may be related to the CXCL16/CXCR6 axis. In conclusion, our study provides the basis and potential strategies for HCC immunotherapy based on NKT cells.

Immunobiology of the biliary tract system

The biliary tract is a complex tubular organ system spanning from the liver to the duodenum. It is the site of numerous acute and chronic disorders, many of unknown origin, that are often associated with cancer development and for which there are limited treatment options. Cholangiocytes with proinflammatory capacities line the lumen and specialised types of immune cells reside in close proximity. Recent technological breakthroughs now permit spatiotemporal assessments of immune cells within distinct niches and have increased our understanding of immune cell tissue residency. In this review, a comprehensive overview of emerging knowledge on the immunobiology of the biliary tract system is provided, with a particular emphasis on the role of distinct immune cells in biliary disorders.

The immunological mechanisms and therapeutic potential in drug-induced liver injury: lessons learned from acetaminophen hepatotoxicity

Acute liver failure caused by drug overdose is a significant clinical problem in developed countries. Acetaminophen (APAP), a widely used analgesic and antipyretic drug, but its overdose can cause acute liver failure. In addition to APAP-induced direct hepatotoxicity, the intracellular signaling mechanisms of APAP-induced liver injury (AILI) including metabolic activation, mitochondrial oxidant stress and proinflammatory response further affect progression and severity of AILI. Liver inflammation is a result of multiple interactions of cell death molecules, immune cell-derived cytokines and chemokines, as well as damaged cell-released signals which orchestrate hepatic immune cell infiltration. The immunoregulatory interplay of these inflammatory mediators and switching of immune responses during AILI lead to different fate of liver pathology. Thus, better understanding the complex interplay of immune cell subsets in experimental models and defining their functional involvement in disease progression are essential to identify novel therapeutic targets for the treatment of AILI. Here, this present review aims to systematically elaborate on the underlying immunological mechanisms of AILI, its relevance to immune cells and their effector molecules, and briefly discuss great therapeutic potential based on inflammatory mediators.

Innate Immune Cells during Machine Perfusion of Liver Grafts-The Janus Face of Hepatic Macrophages

Machine perfusion is an emerging technology in the field of liver transplantation. While machine perfusion has now been implemented in clinical routine throughout transplant centers around the world, a debate has arisen regarding its concurrent effect on the complex hepatic immune system during perfusion. Currently, our understanding of the perfusion-elicited processes involving innate immune cells remains incomplete. Hepatic macrophages (Kupffer cells) represent a special subset of hepatic immune cells with a dual pro-inflammatory, as well as a pro-resolving and anti-inflammatory, role in the sequence of ischemia-reperfusion injury. The purpose of this review is to provide an overview of the current data regarding the immunomodulatory role of machine perfusion and to emphasize the importance of macrophages for hepatic ischemia-reperfusion injury.

New insights into iNKT cells and their roles in liver diseases

Natural killer T cells (NKTs) are an important part of the immune system. Since their discovery in the 1990s, researchers have gained deeper insights into the physiology and functions of these cells in many liver diseases. NKT cells are divided into two subsets, type I and type II. Type I NKT cells are also named iNKT cells as they express a semi-invariant T cell-receptor (TCR) α chain. As part of the innate immune system, hepatic iNKT cells interact with hepatocytes, macrophages (Kupffer cells), T cells, and dendritic cells through direct cell-to-cell contact and cytokine secretion, bridging the innate and adaptive immune systems. A better understanding of hepatic iNKT cells is necessary for finding new methods of treating liver disease including autoimmune liver diseases, alcoholic liver diseases (ALDs), non-alcoholic fatty liver diseases (NAFLDs), and liver tumors. Here we summarize how iNKT cells are activated, how they interact with other cells, and how they function in the presence of liver disease.

Immune mechanisms linking metabolic injury to inflammation and fibrosis in fatty liver disease - novel insights into cellular communication circuits

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and is emerging as the leading cause of cirrhosis, liver transplantation and hepatocellular carcinoma (HCC). NAFLD is a metabolic disease that is considered the hepatic manifestation of the metabolic syndrome; however, during the evolution of NAFLD from steatosis to non-alcoholic steatohepatitis (NASH), to more advanced stages of NASH with liver fibrosis, the immune system plays an integral role. Triggers for inflammation are rooted in hepatic (lipid overload, lipotoxicity, oxidative stress) and extrahepatic (gut-liver axis, adipose tissue, skeletal muscle) systems, resulting in unique immune-mediated pathomechanisms in NAFLD. In recent years, the implementation of single-cell RNA-sequencing and high dimensional multi-omics (proteogenomics, lipidomics) and spatial transcriptomics have tremendously advanced our understanding of the complex heterogeneity of various liver immune cell subsets in health and disease. In NAFLD, several emerging inflammatory mechanisms have been uncovered, including profound macrophage heterogeneity, auto-aggressive T cells, the role of unconventional T cells and platelet-immune cell interactions, potentially yielding novel therapeutics. In this review, we will highlight the recent discoveries related to inflammation in NAFLD, discuss the role of immune cell subsets during the different stages of the disease (including disease regression) and integrate the multiple systems driving inflammation. We propose a refined concept by which the immune system contributes to all stages of NAFLD and discuss open scientific questions arising from this paradigm shift that need to be unravelled in the coming years. Finally, we discuss novel therapeutic approaches to target the multiple triggers of inflammation, including combination therapy via nuclear receptors (FXR agonists, PPAR agonists).

Role of NK T cells in transplantation with particular emphasis on corneal transplantation

Natural killer T cells (NKT cells) are a unique subset of the immune system that possess characteristics of both an innate and adaptive immune response. This study reviews the reported roles of NKT cells in different solid transplantations such as cardiac, skin, liver, and corneal grafts as well as investigates a novel role of NKT cells in steroid-resistant corneal rejections. It is unknown why there is late corneal graft rejection despite being treated with immunosuppression. Our experimental data suggests NKT cells are playing a crucial part in steroid-resistant late graft rejections. While the pathophysiology of acute rejection is better understood, the process of chronic graft rejection is much less clear. Our data suggests NKT cells as a potential therapeutic target to prevent chronic transplant rejection which needs further investigation.

Pathogenesis from Inflammation to Cancer in NASH-Derived HCC

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and one of the deadliest cancers worldwide. As opposed to the majority of patients with HCC, approximately 20–30% of cases of non-alcoholic steatohepatitis (NASH)-derived HCC develop malignant tumours in the absence of liver cirrhosis. NASH is characterized by metabolic dysregulation, chronic inflammation and cell death in the liver, which provide a favorable setting for the transformation of inflammation into cancer. This review aims to describe the pathogenesis and the underlying mechanism of the transition from inflammation to cancer in NASH.

Extrahepatic factors in hepatic immune regulation

The liver is a site of complex immune activity. The hepatic immune system tolerates harmless immunogenic loads in homeostasis status, shelters liver function, while maintaining vigilance against possible infectious agents or tissue damage and providing immune surveillance at the same time. Activation of the hepatic immunity is initiated by a diverse repertoire of hepatic resident immune cells as well as non-hematopoietic cells, which can sense “danger signals” and trigger robust immune response. Factors that mediate the regulation of hepatic immunity are elicited not only in liver, but also in other organs, given the dual blood supply of the liver via both portal vein blood and arterial blood. Emerging evidence indicates that inter-organ crosstalk between the liver and other organs such as spleen, gut, lung, adipose tissue, and brain is involved in the pathogenesis of liver diseases. In this review, we present the features of hepatic immune regulation, with particular attention to the correlation with factors from extrahepatic organ. We describe the mechanisms by which other organs establish an immune association with the liver and then modulate the hepatic immune response. We discuss their roles and distinct mechanisms in liver homeostasis and pathological conditions from the cellular and molecular perspective, highlighting their potential for liver disease intervention. Moreover, we review the available animal models and methods for revealing the regulatory mechanisms of these extrahepatic factors. With the increasing understanding of the mechanisms by which extrahepatic factors regulate liver immunity, we believe that this will provide promising targets for liver disease therapy.

The gut-liver axis in immune remodeling of hepatic cirrhosis

In healthy settings, the gut-liver axis allows host-microbiota communications and mediates immune homeostasis through bidirectional regulation. Meanwhile, in diseases, gut dysbiosis, combined with an impaired intestinal barrier, introduces pathogens and their toxic metabolites into the system, causing massive immune alternations in the liver and other extrahepatic organs. Accumulating evidence suggests that these immune changes are associated with the progression of many liver diseases, especially hepatic cirrhosis. Pathogen-associated molecular patterns that originated from gut microbes directly stimulate hepatocytes and liver immune cells through different pattern recognition receptors, a process further facilitated by damage-associated molecular patterns released from injured hepatocytes. Hepatic stellate cells, along with other immune cells, contribute to this proinflammatory and profibrogenic transformation. Moreover, cirrhosis-associated immune dysfunction, an imbalanced immune status characterized by systemic inflammation and immune deficiency, is linked to gut dysbiosis. Though the systemic inflammation hypothesis starts to link gut dysbiosis to decompensated cirrhosis from a clinical perspective, a clearer demonstration is still needed for the role of the gut-liver-immune axis in cirrhosis progression. This review discusses the different immune states of the gut-liver axis in both healthy and cirrhotic settings and, more importantly, summarizes the current evidence about how microbiota-derived immune remodeling contributes to the progression of hepatic cirrhosis via the gut-liver axis.

Effects of TNF-α deletion on iNKT cell development, activation, and maturation in the steady-state and chronic alcohol-consuming mice

Cytokines play critical roles in regulating iNKT cell development, activation, and maturation. TNF-α co-occurs with iNKT cells in steady-state and many disease conditions. How TNF-α affects iNKT cell function has not been thoroughly investigated. It was found that chronic alcohol consumption enhanced iNKT cell activation and maturation. The underlying mechanism is not known. Herein, a TNF-α KO mouse model was used to address these issues. It was found that the depletion of TNF-α mitigated alcohol consumption-enhanced iNKT cell activation and maturation. In steady-state, depletion of TNF-α did not affect the frequency of iNKT cells in the thymus and spleen but decreased iNKT cells in the liver and increased liver iNKT cell apoptosis. The portion of stage-2 immature iNKT cells increased, stage-3 mature iNKT cells decreased in the thymus of TNF-α KO mice, suggesting that depletion of TNF-α impairs iNKT cell development and maturation. The percentage of CD69+ iNKT cells was significantly lower in the thymus, spleen, and liver of TNF-α KO mice compared to their wild-type littermates, suggesting that depletion of TNF-α inhibits iNKT cell activation. Moreover, the percentage of splenic IL-4- and IFN-γ-producing iNKT cells was significantly lower in TNF-α KO mice than in their wild-type littermates. The depletion of TNF-α increased PLZF+ iNKT cells in the thymus and down-regulated the expression of CD122 on iNKT cells. Collectively, these results support that TNF-α plays a vital role in the regulation of iNKT cell development, activation, and maturation, and alcohol consumption enhances iNKT cell activation and maturation through TNF-α.

Immunological Tolerance in Liver Transplant Recipients: Putative Involvement of Neuroendocrine-Immune Interactions

The transplantation world changed significantly following the introduction of immunosuppressants, with millions of people saved. Several physicians have noted that liver recipients that do not take their medication for different reasons became tolerant regarding kidney, heart, and lung transplantations at higher frequencies. Most studies have attempted to explain this phenomenon through unique immunological mechanisms and the fact that the hepatic environment is continuously exposed to high levels of pathogen-associated molecular patterns (PAMPs) or non-pathogenic microorganism-associated molecular patterns (MAMPs) from commensal flora. These components are highly inflammatory in the periphery but tolerated in the liver as part of the normal components that arrive via the hepatic portal vein. These immunological mechanisms are discussed herein based on current evidence, although we hypothesize the participation of neuroendocrine-immune pathways, which have played a relevant role in autoimmune diseases. Cells found in the liver present receptors for several cytokines, hormones, peptides, and neurotransmitters that would allow for system crosstalk. Furthermore, the liver is innervated by the autonomic system and may, thus, be influenced by the parasympathetic and sympathetic systems. This review therefore seeks to discuss classical immunological hepatic tolerance mechanisms and hypothesizes the possible participation of the neuroendocrine-immune system based on the current literature.

Liver Regeneration in Chronic Liver Injuries: Basic and Clinical Applications Focusing on Macrophages and Natural Killer Cells

BACKGROUND & AIMS

Liver regeneration is a necessary but complex process involving multiple cell types besides hepatocytes. Mechanisms underlying liver regeneration after partial hepatectomy and acute liver injury have been well-described. However, in patients with chronic and severe liver injury, the remnant liver cannot completely restore the liver mass and function, thereby involving liver progenitor-like cells (LPLCs) and various immune cells.

RESULTS

Macrophages are beneficial to LPLCs proliferation and the differentiation of LPLCs to hepatocytes. Also, cells expressing natural killer (NK) cell markers have been studied in promoting both liver injury and liver regeneration. NK cells can promote LPLC-induced liver regeneration, but the excessive activation of hepatic NK cells may lead to high serum levels of interferon-γ, thus inhibiting liver regeneration.

CONCLUSIONS

This review summarizes the recent research on 2 important innate immune cells, macrophages and NK cells, in LPLC-induced liver regeneration and the mechanisms of liver regeneration during chronic liver injury, as well as the latest macrophage- and NK cell-based therapies for chronic liver injury. These novel findings can further help identify new treatments for chronic liver injury, saving patients from the pain of liver transplantations.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Liver Immunity and Therapy

Mesenchymal stem cells (MSCs), as the most common cell source for stem cell therapy, play an important role in the modulation of innate and adaptive immune responses and have been widely used in clinical trials to treat autoimmune and inflammatory diseases. Recent experimental and clinical studies have shown that MSC-derived extracellular vesicles (MSC-EVs) can inhibit the activation and proliferation of a variety of proinflammatory cells, such as Th1, Th17 and M1 macrophages, reducing the secretion of proinflammatory cytokines, while promoting the proliferation of anti-inflammatory cells, such as M2 macrophages and Tregs, and increasing the secretion of anti-inflammatory cytokines, thus playing a role in immune regulation and exhibiting immunomodulatory functions. Besides MSC-EVs are more convenient and less immunogenic than MSCs. There is growing interest in the role of MSC-EVs in liver diseases owing to the intrinsic liver tropism of MSC-EVs. In this review, we focus on the immunomodulatory effects of MSC-EVs and summarize the pivotal roles of MSC-EVs as a cell-free therapy in liver diseases, including NAFLD, AIH, acute liver failure, liver fibrosis and hepatic ischemia–reperfusion injury. Moreover, we provide a concise overview of the potential use and limits of MSC-EVs in clinical application.

Redox Control of Integrin-Mediated Hepatic Inflammation in Systemic Autoimmunity

Significance: Systemic autoimmunity affects 3%-5% of the population worldwide. Systemic lupus erythematosus (SLE) is a prototypical form of such condition, which affects 20-150 of 100,000 people globally. Liver dysfunction, defined by increased immune cell infiltration into the hepatic parenchyma, is an understudied manifestation that affects up to 20% of SLE patients. Autoimmunity in SLE involves proinflammatory lineage specification in the immune system that occurs with oxidative stress and profound changes in cellular metabolism. As the primary metabolic organ of the body, the liver is uniquely capable to encounter oxidative stress through first-pass derivatization and filtering of waste products. Recent Advances: The traffic of immune cells from their development through recirculation in the liver is guided by cell adhesion molecules (CAMs) and integrins, cell surface proteins that tightly anchor cells together. The surface expression of CAMs and integrins is regulated via endocytic traffic that is sensitive to oxidative stress. Reactive oxygen species (ROS) that elicit oxidative stress in the liver may originate from the mitochondria, the cytosol, or the cell membrane. Critical Issues: While hepatic ROS production is a source of vulnerability, it also modulates the development and function of the immune system. In turn, the liver employs antioxidant defense mechanisms to protect itself from damage that can be harnessed to serve as therapeutic mechanisms against autoimmunity, inflammation, and development of hepatocellular carcinoma. Future Directions: This review is aimed at delineating redox control of integrin signaling in the liver and checkpoints of regulatory impact that can be targeted for treatment of inflammation in systemic autoimmunity. Antioxid. Redox Signal. 36, 367-388.

The role of NKT cells in gastrointestinal cancers

Gastrointestinal (GI) cancers represent a complex array of cancers that affect the digestive system. This includes liver, pancreatic, colon, rectal, anal, gastric, esophageal, intestinal and gallbladder cancer. Patients diagnosed with certain GI cancers typically have low survival rates, so new therapeutic approaches are needed. A potential approach is to harness the potent immunoregulatory properties of natural killer T (NKT) cells which are true T cells, not natural killer (NK) cells, that recognize lipid instead of peptide antigens presented by the non-classical major histocompatibility (MHC) molecule CD1d. The NKT cell subpopulation is known to play a vital role in tumor immunity by bridging innate and adaptive immune responses. In GI cancers, NKT cells can contribute to either antitumor or protumor immunity depending on the cytokine profile expressed and type of cancer. This review discusses the complexities of the role of NKT cells in liver, colon, pancreatic and gastric cancers with an emphasis on type I NKT cells.

Immunotherapy for Hepatocellular Carcinoma: New Prospects for the Cancer Therapy

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. HCC patients may benefit from liver transplantation, hepatic resection, radiofrequency ablation, transcatheter arterial chemoembolization, and targeted therapies. The increased infiltration of immunosuppressive immune cells and the elevated expression of immunosuppressive factors in the HCC microenvironment are the main culprits of the immunosuppressive nature of the HCC milieu. The immunosuppressive tumor microenvironment can substantially attenuate antitumoral immune responses and facilitate the immune evasion of tumoral cells. Immunotherapy is an innovative treatment method that has been promising in treating HCC. Immune checkpoint inhibitors (ICIs), adoptive cell transfer (ACT), and cell-based (primarily dendritic cells) and non-cell-based vaccines are the most common immunotherapeutic approaches for HCC treatment. However, these therapeutic approaches have not generally induced robust antitumoral responses in clinical settings. To answer to this, growing evidence has characterized immune cell populations and delineated intercellular cross-talk using single-cell RNA sequencing (scRNA-seq) technologies. This review aims to discuss the various types of tumor-infiltrating immune cells and highlight their roles in HCC development. Besides, we discuss the recent advances in immunotherapeutic approaches for treating HCC, e.g., ICIs, dendritic cell (DC)-based vaccines, non-cell-based vaccines, oncolytic viruses (OVs), and ACT. Finally, we discuss the potentiality of scRNA-seq to improve the response rate of HCC patients to immunotherapeutic approaches.

Non-alcoholic fatty liver disease: the interplay between metabolism, microbes and immunity

Non-alcoholic fatty liver disease (NAFLD) has emerged pandemically across the globe and particularly affects patients with obesity and type 2 diabetes. NAFLD is a complex systemic disease that is characterised by hepatic lipid accumulation, lipotoxicity, insulin resistance, gut dysbiosis and inflammation. In this review, we discuss how metabolic dysregulation, the gut microbiome, innate and adaptive immunity and their interplay contribute to NAFLD pathology. Lipotoxicity has been shown to instigate liver injury, inflammation and insulin resistance. Synchronous metabolic dysfunction, obesity and related nutritional perturbation may alter the gut microbiome, in turn fuelling hepatic and systemic inflammation by direct activation of innate and adaptive immune responses. We review evidence suggesting that, collectively, these unresolved exogenous and endogenous cues drive liver injury, culminating in liver fibrosis and advanced sequelae of this disorder such as liver cirrhosis and hepatocellular carcinoma. Understanding NAFLD as a complex interplay between metabolism, gut microbiota and the immune response will challenge the clinical perception of NAFLD and open new therapeutic avenues.

Identification of liver-specific CD24+ invariant NK T cells with low granzyme B production and high proliferative capacity

Invariant NK T (iNKT) cells are innate-like lymphocytes that can recognize the lipid Ag presented by MHC I like molecule CD1d. Distinct tissue distribution of iNKT cells subsets implies a contribution of these subsets to their related tissue regional immunity. iNKT cells are enriched in liver, an organ with unique immunological properties. Whether liver-specific iNKT cells exist and dedicate to the liver immunity remains elusive. Here, a liver-specific CD24⁺ iNKT subset is shown. Hepatic CD24⁺ iNKT cells show higher levels of proliferation, glucose metabolism, and mTOR activity comparing to CD24^- iNKT cells. Although CD24⁺ iNKT cells and CD24^- iNKT cells in the liver produce similar amounts of cytokines, the hepatic CD24⁺ iNKT cells exhibit lower granzyme B production. These liver-specific CD24⁺ iNKT cells are derived from thymus and differentiate into CD24⁺ iNKT in the liver microenvironment. Moreover, liver microenvironment induces the formation of CD24⁺ conventional T cells as well, and these cells exhibit higher proliferation ability but lower granzyme B production in comparison with CD24^- T cells. The results propose that liver microenvironment might induce the generation of liver-specific iNKT subset that might play an important role in maintaining liver homeostasis.

The Immunological Mechanisms and Immune-Based Biomarkers of Drug-Induced Liver Injury

Drug-induced liver injury (DILI) has become one of the major challenges of drug safety all over the word. So far, about 1,100 commonly used drugs including the medications used regularly, herbal and/or dietary supplements, have been reported to induce liver injury. Moreover, DILI is the main cause of the interruption of new drugs development and drugs withdrawn from the pharmaceutical market. Acute DILI may evolve into chronic DILI or even worse, commonly lead to life-threatening acute liver failure in Western countries. It is generally considered to have a close relationship to genetic factors, environmental risk factors, and host immunity, through the drug itself or its metabolites, leading to a series of cellular events, such as haptenization and immune response activation. Despite many researches on DILI, the specific biomarkers about it are not applicable to clinical diagnosis, which still relies on the exclusion of other causes of liver disease in clinical practice as before. Additionally, circumstantial evidence has suggested that DILI is mediated by the immune system. Here, we review the underlying mechanisms of the immune response to DILI and provide guidance for the future development of biomarkers for the early detection, prediction, and diagnosis of DILI.

A digital health platform for assisting the diagnosis and monitoring of COVID-19 progression: An adjuvant approach for augmenting the antiviral response and mitigating the immune-mediated target organ damage

Coronavirus disease 2019 (COVID-19), which is a respiratory illness associated with high mortality, has been classified as a pandemic. The major obstacles for the clinicians to contain the disease are limited information availability, difficulty in disease diagnosis, predicting disease prognosis, and lack of disease monitoring tools. Additionally, the lack of valid therapies has further contributed to the difficulties in containing the pandemic. Recent studies have reported that the dysregulation of the immune system leads to an ineffective antiviral response and promotes pathological immune response, which manifests as ARDS, myocarditis, and hepatitis. In this study, a novel platform has been described for disseminating information to physicians for the diagnosis and monitoring of patients with COVID-19. An adjuvant approach using compounds that can potentiate antiviral immune response and mitigate COVID-19-induced immune-mediated target organ damage has been presented. A prolonged beneficial effect is achieved by implementing algorithm-based individualized variability measures in the treatment regimen.

SRSF1 plays a critical role in invariant natural killer T cell development and function

Invariant natural killer T (iNKT) cells are highly conserved innate-like T lymphocytes that originate from CD4⁺CD8⁺ double-positive (DP) thymocytes. Here, we report that serine/arginine splicing factor 1 (SRSF1) intrinsically regulates iNKT cell development by directly targeting Myb and balancing the abundance of short and long isoforms. Conditional ablation of SRSF1 in DP cells led to a substantially diminished iNKT cell pool due to defects in proliferation, survival, and TCRα rearrangement. The transition from stage 0 to stage 1 of iNKT cells was substantially blocked, and the iNKT2 subset was notably diminished in SRSF1-deficient mice. SRSF1 deficiency resulted in aberrant expression of a series of regulators that are tightly correlated with iNKT cell development and iNKT2 differentiation, including Myb, PLZF, Gata3, ICOS, and CD5. In particular, we found that SRSF1 directly binds and regulates pre-mRNA alternative splicing of Myb and that the expression of the short isoform of Myb is substantially reduced in SRSF1-deficient DP and iNKT cells. Strikingly, ectopic expression of the Myb short isoform partially rectified the defects caused by ablation of SRSF1. Furthermore, we confirmed that the SRSF1-deficient mice exhibited resistance to acute liver injury upon α-GalCer and Con A induction. Our findings thus uncovered a previously unknown role of SRSF1 as an essential post-transcriptional regulator in iNKT cell development and functional differentiation, providing new clinical insights into iNKT-correlated disease.

The Wnt/β-catenin signaling pathway in the tumor microenvironment of hepatocellular carcinoma

The Wnt/β-catenin signaling pathway regulates many aspects of tumor biology, and many studies have focused on the role of this signaling pathway in tumor cells. However, it is now clear that tumor development and metastasis depend on the two-way interaction between cancer cells and their environment, thereby forming a tumor microenvironment (TME). In this review, we discuss how Wnt/β-catenin signaling regulates cross-interactions among different components of the TME, including immune cells, stem cells, tumor vasculature, and noncellular components of the TME in hepatocellular carcinoma. We also investigate their preclinical and clinical insights for primary liver cancer intervention, and explore the significance of using Wnt/β-catenin mutations as a biomarker to predict resistance in immunotherapy.

Augmented antiviral T cell immunity by oral administration of IMM-124E in preclinical models and a phase I/IIa clinical trial: A method for the prevention and treatment of COVID-19

Biological adjuvants that target the gut immune system are being developed for modulating the immune system. Hyperimmune bovine colostrum (HBC), produced by harvesting the bovine colostrum of dairy cows immunized to exogenous antigens, has been shown to modulate the immune responses and alleviate immune‐mediated organ damages. The aim of the present study was to determine the ability of HBC to promote antiviral interferonγ (IFNγ) T cell responses. In a preclinical study, mice were orally administered with HBC for 5 days and tested for the number of T cell clones secreting IFNγ in response to viral antigens of the swine flu, New Caledonia influenza, and cytomegalovirus. In a phase I/IIa clinical trial, five healthy volunteers were treated for 5 days with HBC followed by testing the anti‐coronavirus disease (COVID‐19) immunity. In the preclinical study, oral administration of HBC augmented the number of T cell clones secreting IFNγ in response to viral antigens. In the clinical trial, oral administration of HBC to healthy males significantly increased the number of anti‐COVID‐19 spike protein IFNγ positive T cell clones. Oral administration of HBC provides a novel method for augmenting antiviral responses. Its high‐safety profile makes it ideal for all disease stages and for pre‐emptive therapy among medical personnel and other workers who are at a high risk of exposure to infections. The relatively low cost of HBC is expected to minimize care provider burdens, costs, and enable its global application.