The development and progression of liver cirrhosis are considerably influenced by immune processes, with CD8 + T cells playing a key role. Notably, cytokines can activate bystander CD38 + HLA-DR + CD8 + T cells without the need for T cell receptor (TCR) stimulation. However, their role in liver fibrosis remains controversial. This study aimed to investigate the pathological role of CD38 + HLA-DR + CD8 + T cells in cirrhosis progression and explore the mechanisms that regulate their functions. Peripheral blood mononuclear cells (PBMCs) were extracted from patients with cirrhosis and healthy donors, and the ratio of CD38+HLA-DR+CD8+ T cells was assessed through flow cytometry. The relationship between the prevalence of these cells and certain clinical indicators was investigated. Additionally, CD8+ T cells from healthy donors were used to examine the impact of cytokine IL-15 on CD38+HLA-DR+CD8+ T cells, utilizing flow cytometry and in vitro cytotoxicity assays. Finally, the signaling pathways involved in IL-15 activation of CD38+HLA-DR+CD8+ T cells were examined in vitro. The proportion of CD38+HLA-DR+CD8+ T cells was significantly increased in patients with cirrhosis compared to healthy donors and exhibited a strong correlation with disease severity, hepatic damage, and inflammation in cirrhosis. IL-15-stimulated CD38+HLA-DR+CD8+ T cells from healthy donors demonstrated proliferation and overexpression of cytotoxic molecules, exhibiting NKG2D- and FasL-dependent innate-like cytotoxicity without TCR activation. Notably, IL-15 did not alter the mitochondrial function of these cells. The JAK/STAT5 and PI3K/mTOR pathways were found to play a critical role in IL-15-induced innate-like cytotoxicity. These findings suggested that CD38+HLA-DR+CD8+ T cells from patients with cirrhosis contribute to immune-mediated liver injury. Furthermore, the JAK/STAT5 and PI3K/mTOR pathways were essential for IL-15-induced activation of CD38+HLA-DR+CD8+ T cells, which expressed NKG2D and FasL, demonstrating innate cytotoxicity independent of TCR engagement.

Long-COVID immunopathogenesis involves diverse factors. We longitudinally characterize hospitalized COVID-19 patients, examining the role of SARS-CoV-2 RNAemia and inflammation in immune dysregulation.

Hospitalized patients are evaluated during acute infection (T0), 3 months post-symptom onset (T1), and 3 years if symptoms persisted (T2). Immune profile includes characterization of SARS-CoV-2-specific/non-specific T/B cells (flow cytometry) and antibodies (ELISA, neutralization, ADCC). RNAemia and cytokines are quantified (RT-PCR, cytometric beads array) and correlated.

non-parametric cross-sectional, longitudinal and correlation analyses.

Here we show 48 hospitalized individuals during acute COVID-19, 38 exhibit early persistent symptoms (EPS+) 3 months post-symptoms onset, 10 do not (EPS-). Groups are comparable for age, sex, co-morbidities. The EPS+ shows fatigue, dyspnoea, anosmia/dysgeusia, diarrhea, chronic pain, mnestic disorders. Over time, they show a reduction of neutralization ability and total SARS-CoV-2-specific CD4 T cells, with increased total CD4 TEMRA, and failure to increase RBD-specific B cells and IgA+ MBCs. EPS+ patients show higher levels of T0-IFN-γ + CD4 TEMRA, T1-IL-2 + CD4 TEM and T1-TNF-α + CD4 cTfh. In EPS+, baseline SARS-CoV-2 RNAemia positively correlates with CD4 TEMRA, follow-up SARS-CoV-2 RNAemia with ADCC. Among 38 EPS+ individuals at T1, 33 are evaluated 3 years after infection, 5 are lost at follow-up. 10/33 EPS+ show long-term symptoms (late persistent symptoms, EPS + LPS+), whereas 23/33 fully recover (EPS + LPS-). Antibodies, RNAemia, and cytokines show no differences between/within groups at any time point.

Early persistent symptoms are associated with multi-layered SARS-CoV-2-specific/non-SARS-CoV-2-specific immune dysregulation. The shift towards non-Ag-specific TEMRA and ADCC trigger in EPS+ may relate to SARS-CoV-2 RNAemia. Early immune dysregulation does not associate with long-term persistent symptoms. Further research on SARS-CoV-2 RNAemia and early immune dysregulation is needed.

Aberrant immune response is a hallmark of asthma, with 5%-10% of patients suffering from severe disease exhibiting poor response to standard treatment. A better understanding of the immune responses contributing to disease heterogeneity is critical for improving asthma management. T cells are major players in the orchestration of asthma, in both mild and severe disease, but it is unclear whether specific T cell subsets influence asthma symptom duration. Here we show a significant association of airway CD8+ effector memory T cells re-expressing CD45RA (TEMRAs), but not CD8+CD45RO+ or tissue-resident memory T cells, with asthma duration in patients with severe asthma (SA) but not mild to moderate asthma (MMA). Higher frequencies of IFN-γ+CD8+ TEMRAs compared with IFN-γ+CD45RO+ T cells were detected in SA airways, and the TEMRAs from patients with SA but not MMA proliferated ex vivo, although both expressed cellular senescence-associated biomarkers. Prompted by the transcriptomic profile of SA CD8+ TEMRAs and proliferative response to IL-15, airway IL15 expression was higher in patients with SA compared with MMA. Additionally, IL15 expression in asthmatic airways negatively correlated with lung function. Our findings add what we believe is a new dimension to understanding asthma heterogeneity, identifying IL-15 as a potential target for treatment.

Gut-liver crosstalk plays an important role in alcohol-associated liver disease (ALD) pathogenesis; but underlying mechanisms remain obscure.

We examined the regulation of intestinal and intrahepatic CD8+ T lymphocytes and their contribution to ALD.

ALD patients were recruited for evaluation of intestinal and liver T cells. Single-cell RNA sequencing (scRNA seq) was performed to analyse intrahepatic and peripheral T cells in ALD. Wildtype, CD8-specific Bcl2 transgenic (Cd8 Bcl-2), and Cd8 -/- mice were subjected to chronic-plus-binge ethanol feeding.

In ALD patients, duodenal CD8+ T cells were selectively reduced and negatively correlated with liver injury and bacterial translocation markers, while intrahepatic CD8+ T cells were markedly increased. ScRNA seq analysis of ALD patient livers revealed several populations of CD8+ T cells expressing activation and survival genes (eg, Bcl2). Transcriptomics and functional studies revealed a key role of prosurvival BCL2 in this opposite regulation of CD8+ T cells. Mechanistically, chronic-plus-binge ethanol feeding reduced CD8+ T cells specifically in the duodenum where ethanol levels are high. Inducing BCL2 in CD8+ T cells reversed ethanol-induced loss of duodenal CD8+ T cells, improved gut barrier function and ameliorated ALD, while CD8 deficiency was linked to enhanced neutrophil and macrophage infiltration in the liver, exacerbating ALD in mice.

ALD is associated with loss of duodenal CD8+ T cells but elevation of intrahepatic CD8+ T cells, which aggravates and ameliorates ALD, respectively. Restoration of survival and functions of intestinal and intrahepatic CD8+ T cells may represent a novel therapeutic strategy for ALD patients.

A key feature of cytotoxic CD8+ T cells for eliminating pathogens and malignant cells is their capacity to produce proinflammatory cytokines, which include TNF and IFNγ. Provided that these cytokines are highly toxic, a tight control of their production is imperative. RNA-binding proteins (RBPs) are essential for the fine-tuning of cytokine production. The role of the RBP ZFP36L1 and its sister protein ZFP36L2 herein has been established, but their relative contribution to cytokine production is not well understood. We here compared the effect of ZFP36L1 and ZFP36L2 single and double deficiency in murine effector CD8+ T cells. Whereas single deficient T cells significantly increased cytokine production, double deficiency completely unleashed the cytokine production. Not only the TNF production was substantially prolonged in double-deficient T cells. Also, the production of IFNγ reached unprecedented levels with >90% IFNγ-producing T cells compared with 3% in WT T cells after 3 days of continuous activation. This continuous cytokine production by double-deficient T cells was also observed in tumor-infiltrating lymphocytes in vivo, however, with no effect on tumor growth. ZFP36L1 and ZFP36L2 double deficiency resulted in decreased cell viability, impaired STAT5 signaling, and dysregulated cell cycle progression. In conclusion, while combined deletion in ZFP36L1 and ZFP36L2 can drive continuous cytokine production even upon chronic activation, safeguards are in place to counteract such super-cytokine producers.

Liver tissue-resident memory T (TRM) cells play a pivotal role in hepatic immune responses. Their unique residence within liver sinusoids allow continuous antigen surveillance. In this review, we highlight the role of liver TRM cells in protective immunity and disease pathology. Comparisons between human and murine liver TRM cells reveal species-specific characteristics, suggesting the need for human-focused studies. One key finding is the involvement of liver TRM cells in viral hepatitis, where they can both control infection and contribute to liver damage. Liver TRM cells also exhibit dual roles in metabolic-associated steatotic liver disease, promoting inflammation and fibrosis while also contributing to fibrosis resolution. In autoimmune liver diseases, such as autoimmune hepatitis and primary sclerosing cholangitis, the presence of liver TRM cells correlates with disease severity. In this review, we underscore the importance of liver TRM cells in vaccine development, particularly vaccines against malaria. Future research should focus on the mechanisms governing TRM-cell formation, maintenance, and function, with the aim of supporting their protective roles while mitigating detrimental effects. Advancing our understanding of liver TRM cells will enhance our knowledge of liver immunology and inform novel therapeutic strategies for liver disease management.

Most children with acute hepatitis A virus (HAV) or hepatitis E virus (HEV) infection are asymptomatic. Bystander CD8+ T-cell activation has garnered attention owing to its possible pathophysiological role in adult hepatitis. However, no reports have studied it in pediatric hepatitis. Herein, we describe the case of a three-year-old girl with acute hepatitis by HEV genotype 1. She had a history of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infections, and HEV hepatitis occurred shortly after asymptomatic HAV infection. Peripheral immunophenotyping revealed activation of non-HEV-specific CD8+ T cells which include EBV-specific and CMV-specific CD8+ T cells, during the acute phase. While alanine-aminotransferase levels declined after admission, the total number of activated CD8+ T cells increased for four days after admission and decreased thereafter. In contrast, activation of EBV-specific and CMV-specific CD8+ T cells was almost at the maximal level at the time of admission, which suggest development of activated bystander CD8+ T cells in the early stage. This case highlights the significance of the bystander CD8+ T-cell activation even in pediatric hepatitis and the size of the CD8+ T cell memory pool in the individuals for the development of hepatitis, given the patient's history of infections with EBV, CMV and HAV.

The immune system is endowed with the capacity to distinguish between self and non-self, so-called immune tolerance or "consciousness of the immune system." This type of awareness is designed to achieve host protection by eliminating cells expressing a wide range of non-self antigens including microbial-derived peptides. Such a successful immune response is associated with the secretion of a whole spectrum of soluble mediators, e.g., cytokines and chemokines, which not only contribute to the clearance of infected host cells but also activate T cells that are not specific to the original cognate antigen. This kind of non-specific T-cell activation is called "bystander activation." Although it is well-established that this phenomenon is cytokine-dependent, there is evidence in the literature showing the involvement of peptide/MHC recognition depending on the type of T-cell subset (naive vs. memory). Here, we will summarize our current understanding of the mechanism(s) of bystander T-cell activation as well as its biological significance in a wide range of diseases including microbial infections, cancer, auto- and alloimmunity, and chronic inflammatory diseases such as atherosclerosis.

CD8+ T cells play a critical role in the immune dysfunction associated with liver cirrhosis. CD38+HLA-DR+CD8+ T cells, or bystander-activated CD8+ T cells, are involved in tissue injury but their specific contribution to liver cirrhosis remains unclear. This study sought to identify the mechanism for CD38+HLA-DR+CD8+ T cell-mediated pathogenesis during liver cirrhosis.

The immunophenotype, antigen specificity, cytokine secretion and cytotoxicity-related indicators of CD38+HLA-DR+CD8+ T cells were determined using flow cytometry. The functional properties of these cells were assessed using transcriptome analysis. CD38+HLA-DR+CD8+ T-cell killing was detected using cytotoxicity and antibody-blocking assays.

The proportion of CD38+HLA-DR+CD8+ T cells was significantly elevated in liver cirrhosis patients and correlated with tissue damage. Transcriptome analysis revealed that these cells had innate-like functional characteristics. This CD8+ T-cell population primarily consisted of effector memory T cells and produced a high level of cytotoxicity-related cytokines, granzyme B and perforin. IL-15 promoted CD38+HLA-DR+CD8+ T-cell activation and proliferation, inducing significant TCR-independent cytotoxicity mediated through NKG2D.

CD38+HLA-DR+CD8+ T cells correlated with cirrhosis-related liver injury and contributed to liver damage by signalling through NKG2D in a TCR-independent manner.

Regulatory T cells (Tregs) are well-known to mediate peripheral tolerance at homeostasis, and there is a growing appreciation for their role in modulating infectious disease immunity. Following acute and chronic infections, Tregs can restrict pathogen-specific T cell responses to limit immunopathology. However, it is unclear if Tregs mediate control of pathology and immunity in distal tissue sites during localized infections. We investigated the role of Tregs in immunity and disease in various tissue compartments in the context of "mild" vaginal Zika virus infection. We found that Tregs are critical to generating robust virus-specific CD8 T cell responses in the initial infection site. Further, Tregs limit inflammatory cytokines and immunopathology during localized infection; a dysregulated immune response in Treg-depleted mice leads to increased T cell infiltrates and immunopathology in both the vagina and the central nervous system (CNS). Importantly, these CNS infiltrates are not present at the same magnitude during infection of Treg-sufficient mice, in which there is no CNS immunopathology. Our data suggest that Tregs are necessary to generate a robust virus-specific response at the mucosal site of infection, while Treg-mediated restriction of bystander inflammation limits immunopathology both at the site of infection as well as distal tissue sites.

Acute liver failure (ALF) is a rare cause of liver-related mortality worldwide, with an estimated annual global incidence of more than one million cases. While drug-induced liver injury, including acetaminophen toxicity, is the leading cause of ALF in the Western world, viral infections remain a significant cause of ALF and the most common cause in many developing nations. Given the high mortality rates associated with ALF, healthcare providers should be aware of the broad range of viral infections that have been implicated to enable early diagnosis, rapid treatment initiation when possible, and optimal management, which may include liver transplantation. This review aims to provide a summary of viral causes of ALF, diagnostic approaches, treatment options, and expected outcomes.

CD8 T cells are crucial adaptive immune cells with cytotoxicity to fight against pathogens or abnormal self-cells via major histocompatibility complex class I-dependent priming pathways. The composition of the memory CD8 T-cell pool is influenced by various factors. Physiological aging, chronic viral infection, and autoimmune diseases promote the accumulation of CD8 T cells with highly differentiated memory phenotypes. Accumulating studies have shown that some of these memory CD8 T cells also exhibit innate-like cytotoxicity and upregulate the expression of receptors associated with natural killer (NK) cells. Further analysis shows that these NK-like CD8 T cells have transcriptional profiles of both NK and CD8 T cells, suggesting the transformation of CD8 T cells into NK cells. However, the specific induction mechanism underlying NK-like transformation and the implications of this process for CD8 T cells are still unclear. This review aimed to deduce the possible differentiation model of NK-like CD8 T cells, summarize the functions of major NK-cell receptors expressed on these cells, and provide a new perspective for exploring the role of these CD8 T cells in health and disease.

Memory CD8 T cells (Tmem) can be activated into innate-like killers by cytokines like IL-12, IL-15, and/or IL-18; but mechanisms regulating this phenomenon (termed bystander activation) are not fully resolved. We found strain-intrinsic deficiencies in bystander activation using specific pathogen-free mice, whereby basal IL-4 signals antagonize IL-18 sensing. We show that therapeutic and helminth-induced IL-4 impairs protective bystander-mediated responses against pathogens. However, this IL-4/IL-18 axis does not completely abolish bystander activation but rather tunes the expression of direct versus indirect mediators of cytotoxicity (granzymes and interferon-γ, respectively). We show that antigen-experience overrides strain-specific deficiencies in bystander activation, leading to uniform IL-18 receptor expression and enhanced capacity for bystander activation/cytotoxicity. Our data highlight that bystander activation is not a binary process but tuned/deregulated by other cytokines that are elevated by contemporaneous infections. Further, our findings underscore the importance of antigen-experienced Tmem to dissect the contributions of bystander Tmem in health and disease.

Through immune memory, infections have a lasting effect on the host. While memory cells enable accelerated and enhanced responses upon rechallenge with the same pathogen, their impact on susceptibility to unrelated diseases is unclear. We identify a subset of memory T helper 1 (Th1) cells termed innate acting memory T (TIA) cells that originate from a viral infection and produce IFN-γ with innate kinetics upon heterologous challenge in vivo. Activation of memory TIA cells is induced in response to IL-12 in combination with IL-18 or IL-33 but is TCR independent. Rapid IFN-γ production by memory TIA cells is protective in subsequent heterologous challenge with the bacterial pathogen Legionella pneumophila. In contrast, antigen-independent reactivation of CD4+ memory TIA cells accelerates disease onset in an autoimmune model of multiple sclerosis. Our findings demonstrate that memory Th1 cells can acquire additional TCR-independent functionality to mount rapid, innate-like responses that modulate susceptibility to heterologous challenges.

Patients with advanced cirrhosis often develop hepatic decompensation, which is accompanied by systemic inflammation and may eventually lead to acute-on-chronic liver failure. One important cause of systemic hyperinflammation is a dysregulated overshooting immune response in ascites in the abdominal cavity. In this study, we analyzed the role of CD8+ T cells in the ascites immune compartment.

Peripheral blood and ascites fluid were collected from 50 patients with decompensated cirrhosis. Phenotype and functional responses of CD8+ T cells were analyzed, and obtained data were compared with each other as well as with healthy controls and patients with compensated cirrhosis.

High-dimensional flow cytometry revealed that CD8+ T cells are abundant in the ascites of patients with cirrhosis and exhibit a chronically activated bystander phenotype with innate-like functions. Indeed, we identified distinct CXCR6+CD69+ clusters of late effector memory CD8+ T cells that were rarely found in blood and correlated with clinical parameters of disease severity. Moreover, this CD8+ T-cell population was hyperresponsive to innate cytokines and exhibited cytokine-mediated bystander activation. Interestingly, the Janus kinase (JAK) inhibitor tofacitinib was able to effectively block bystander-activated CXCR6+CD69+ CD8+ T cells and significantly suppress effector molecule production.

The results indicate that CXCR6+CD69+ CD8+ T cells in ascites are associated with disease severity and may contribute to inflammation in patients with decompensated cirrhosis, suggesting that targeted inhibition of this immune cell subset may be a viable therapeutic option.

Patients with advanced cirrhosis often develop hepatic decompensation, which is accompanied by systemic inflammation and eventually leads to acute-on-chronic liver failure. One important cause of systemic hyperinflammation is a dysregulated overshooting immune response in ascites in the abdominal cavity. In this study, we demonstrate that CXCR6+CD69+ CD8+ T cells are abundant in the ascites of patients with cirrhosis, exhibit a chronically activated bystander phenotype, and correlate with clinical parameters of disease severity. Moreover, we show that the Janus kinase (JAK) inhibitor tofacitinib can effectively block these bystander-activated CXCR6+CD69+ CD8+ T cells, suggesting that targeted inhibition of this immune cell subset may be a potential therapeutic strategy.

Prospective registry: INFEKTA (DRKS00010664).

Tissue-resident memory CD8+T cells (CD8+TRMs) are thought to play a crucial role in cancer immunosurveillance. However, the characteristics of CD8+TRMs in the tumor microenvironment (TME) of human non-small cell lung cancer (NSCLC) remain unclear. Here, we report that CD8+TRMs accumulate explicitly and exhibit a unique gene expression profile in the TME of NSCLC. Interestingly, these tumor-associated CD8+TRMs uniquely exhibit an innate-like phenotype. Importantly, we found that junction adhesion molecule-like (JAML) provides an alternative costimulatory signal to activate tumor-associated CD8+TRMs via combination with cancer cell-derived CXADR (CXADR Ig-like cell adhesion molecule). Furthermore, we demonstrated that activating JAML could promote the expression of TLR1/2 on CD8+TRMs, inhibit tumor progression and prolong the survival of tumor-bearing mice. Finally, we found that higher CD8+TRMs and JAML expression in the TME could predict favorable clinical outcomes in NSCLC patients. Our study reveals an intrinsic bias of CD8+TRMs for receiving the tumor-derived costimulatory signal in the TME, which sustains their innate-like function and antitumor role. These findings will shed more light on the biology of CD8+TRMs and aid in the development of potential targeted treatment strategies for NSCLC.

Cytolytic CD8+ T cells mediate immunopathology in cutaneous leishmaniasis without controlling parasites. Here, we identify factors involved in CD8+ T cell migration to the lesion that could be targeted to ameliorate disease severity. CCR5 was the most highly expressed chemokine receptor in patient lesions, and the high expression of CCL3 and CCL4, CCR5 ligands, was associated with delayed healing of lesions. To test the requirement for CCR5, Leishmania-infected Rag1-/- mice were reconstituted with CCR5-/- CD8+ T cells. We found that these mice developed smaller lesions accompanied by a reduction in CD8+ T cell numbers compared to controls. We confirmed these findings by showing that the inhibition of CCR5 with maraviroc, a selective inhibitor of CCR5, reduced lesion development without affecting the parasite burden. Together, these results reveal that CD8+ T cells migrate to leishmanial lesions in a CCR5-dependent manner and that blocking CCR5 prevents CD8+ T cell-mediated pathology.

Autologous stem cell transplantation (ASCT) is the standard of care consolidation therapy for eligible patients with myeloma but most patients eventually progress, an event associated with features of immune escape. Novel approaches to enhance antimyeloma immunity after ASCT represent a major unmet need. Here, we demonstrate that patient-mobilized stem cell grafts contain high numbers of effector CD8 T cells and immunosuppressive regulatory T cells (Tregs). We showed that bone marrow (BM)-residing T cells are efficiently mobilized during stem cell mobilization (SCM) and hypothesized that mobilized and highly suppressive BM-derived Tregs might limit antimyeloma immunity during SCM. Thus, we performed ASCT in a preclinical myeloma model with or without stringent Treg depletion during SCM. Treg depletion generated SCM grafts containing polyfunctional CD8 T effector memory cells, which dramatically enhanced myeloma control after ASCT. Thus, we explored clinically tractable translational approaches to mimic this scenario. Antibody-based approaches resulted in only partial Treg depletion and were inadequate to recapitulate this effect. In contrast, a synthetic interleukin-2 (IL-2)/IL-15 mimetic that stimulates the IL-2 receptor on CD8 T cells without binding to the high-affinity IL-2Ra used by Tregs efficiently expanded polyfunctional CD8 T cells in mobilized grafts and protected recipients from myeloma progression after ASCT. We confirmed that Treg depletion during stem cell mobilization can mitigate constraints on tumor immunity and result in profound myeloma control after ASCT. Direct and selective cytokine signaling of CD8 T cells can recapitulate this effect and represent a clinically testable strategy to improve responses after ASCT.

CD8 T cells provide immunity to virus infection through recognition of epitopes presented by peptide major histocompatibility complexes (pMHCs). To establish a concise panel of widely recognized T cell epitopes from common viruses, we combined analysis of TCR down-regulation upon stimulation with epitope-specific enumeration based on barcode-labeled pMHC multimers. We assess CD8 T cell binding and reactivity for 929 previously reported epitopes in the context of 1 of 25 HLA alleles representing 29 viruses. The prevalence and magnitude of CD8 T cell responses were evaluated in 48 donors and reported along with 137 frequently recognized virus epitopes, many of which were underrepresented in the public domain. Eighty-four percent of epitope-specific CD8 T cell populations demonstrated reactivity to peptide stimulation, which was associated with effector and long-term memory phenotypes. Conversely, nonreactive T cell populations were associated primarily with naive phenotypes. Our analysis provides a reference map of epitopes for characterizing CD8 T cell responses toward common human virus infections.

Although immune cell therapy has long been used for treating solid cancer, its efficacy remains limited. Interferon (IFN)-producing killer dendritic cells (IKDCs) exhibit cytotoxicity and present antigens to relevant cells; thus, they can selectively induce tumor-associated antigen (TAA)-specific CD8 T cells and may be useful in cancer treatment. Various protocols have been used to amplify human IKDCs from peripheral sources, but the complexity of the process has prevented their widespread clinical application. Additionally, the induction of TAA-specific CD8 T cells through the adoptive transfer of IKDCs to immunocompromised patients with cancer may be insufficient. Therefore, we developed a method for generating an immune cell-based regimen, Phyduxon-T, comprising a human IKDC counterpart (Phyduxon) and expanded TAA-specific CD8 T cells.

Peripheral blood mononuclear cells from ovarian cancer patients were cultured with human interleukin (hIL)-15, hIL-12, and hIL-18 to generate Phyduxon-T. Then, its phenotype, cytotoxicity, and antigen-presenting function were evaluated through flow cytometry using specific monoclonal antibodies.

Phyduxon exhibited the characteristics of both natural killer and dendritic cells. This regimen also exhibited cytotoxicity against primary ovarian cancer cells and presented TAAs, thereby inducing TAA-specific CD8 T cells, as evidenced by the expression of 4-1BB and IFN-γ. Notably, the Phyduxon-T manufacturing protocol effectively expanded IFN-γ-producing 4-1BB+ TAA-specific CD8 T cells from peripheral sources; these cells exhibited cytotoxic activities against ovarian cancer cells.

Phyduxon-T, which is a combination of natural killer cells, dendritic cells, and TAA-specific CD8 T cells, may enhance the efficacy of cancer immunotherapy.

After a century of using the Bacillus Calmette-Guérin (BCG) vaccine, our understanding of its ability to provide protection against homologous (Mycobacterium tuberculosis) or heterologous (for example, influenza virus) infections remains limited. Here we show that systemic (intravenous) BCG vaccination provides significant protection against subsequent influenza A virus infection in mice. We further demonstrate that the BCG-mediated cross-protection against influenza A virus is largely due to the enrichment of conventional CD4+ effector CX3CR1hi memory αβ T cells in the circulation and lung parenchyma. Importantly, pulmonary CX3CR1hi T cells limit early viral infection in an antigen-independent manner via potent interferon-γ production, which subsequently enhances long-term antimicrobial activity of alveolar macrophages. These results offer insight into the unknown mechanism by which BCG has persistently displayed broad protection against non-tuberculosis infections via cross-talk between adaptive and innate memory responses.

Cytokines play pleiotropic roles in human health and disease by regulating both innate and adaptive immune responses. Interleukins (ILs), a large group of cytokines, can be divided into seven families, including IL-1, IL-2, IL-6, IL-8, IL-10, IL-12, and IL-17 families. Here, we review the functions of ILs in the pathogenesis and resolution of liver diseases, such as liver inflammation (e.g., IL-35), alcohol-related liver disease (e.g., IL-11), non-alcoholic steatohepatitis (e.g., IL-22), liver fibrosis (e.g., Il-17a), and liver cancer (e.g., IL-8). Overall, IL-1 family members are implicated in liver inflammation induced by different etiologies, such as alcohol consumption, high-fat diet, and hepatitis viruses. IL-2 family members mainly regulate T lymphocyte and NK cell proliferation and activation, and the differentiation of T cells. IL-6 family cytokines play important roles in acute phase response in liver infection, liver regeneration, and metabolic regulation, as well as lymphocyte activation. IL-8, also known as CXCL8, is activated in chronic liver diseases, which is associated with the accumulation of neutrophils and macrophages. IL-10 family members contribute key roles to liver immune tolerance and immunosuppression in liver disease. IL-12 family cytokines influence T-cell differentiation and play an essential role in autoimmune liver disease. IL-17 subfamilies contribute to infection defense, liver inflammation, and Th17 cell differentiation. ILs interact with different type I and type II cytokine receptors to regulate intracellular signaling pathways that mediate their functions. However, most clinical studies are only performed to evaluate IL-mediated therapies on alcohol and hepatitis virus infection-induced hepatitis. More pre-clinical and clinical studies are required to evaluate IL-mediated monotherapy and synergistic therapies.

Although many viral infections are linked to the development of neurological disorders, the mechanism governing virus-induced neuropathology remains poorly understood, particularly when the virus is not directly neuropathic. Using a mouse model of Zika virus (ZIKV) infection, we found that the severity of neurological disease did not correlate with brain ZIKV titers, but rather with infiltration of bystander activated NKG2D+CD8+ T cells. Antibody depletion of CD8 or blockade of NKG2D prevented ZIKV-associated paralysis, suggesting that CD8+ T cells induce neurological disease independent of TCR signaling. Furthermore, spleen and brain CD8+ T cells exhibited antigen-independent cytotoxicity that correlated with NKG2D expression. Finally, viral infection and inflammation in the brain was necessary but not sufficient to induce neurological damage. We demonstrate that CD8+ T cells mediate virus-induced neuropathology via antigen-independent, NKG2D-mediated cytotoxicity, which may serve as a therapeutic target for treatment of virus-induced neurological disease.

IL-15 belongs to the common gamma chain cytokine family and has pleiotropic immunological functions. IL-15 is a homeostatic cytokine essential for the development and maintenance of NK cells and memory CD8+ T cells. In addition, IL-15 plays a critical role in the activation, effector functions, tissue residency, and senescence of CD8+ T cells. IL-15 also activates virtual memory T cells, mucosal-associated invariant T cells and γδ T cells. Recently, IL-15 has been highlighted as a major trigger of TCR-independent activation of T cells. This mechanism is involved in T cell-mediated immunopathogenesis in diverse diseases, including viral infections and chronic inflammatory diseases. Deeper understanding of IL-15-mediated T-cell responses and their underlying mechanisms could optimize therapeutic strategies to ameliorate host injury by T cell-mediated immunopathogenesis. This review highlights recent advancements in comprehending the role of IL-15 in relation to T cell responses and immunopathogenesis under various host conditions.

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.

Extensive, large-scale single-cell profiling of healthy human blood at different ages is one of the critical pending tasks required to establish a framework for the systematic understanding of human aging. Here, using single-cell RNA/T cell receptor (TCR)/BCR-seq with protein feature barcoding, we profiled 317 samples from 166 healthy individuals aged 25-85 years old. From this, we generated a dataset from ∼2 million cells that described 55 subpopulations of blood immune cells. Twelve subpopulations changed with age, including the accumulation of GZMK+CD8+ T cells and HLA-DR+CD4+ T cells. In contrast to other T cell memory subsets, transcriptionally distinct NKG2C+GZMB-CD8+ T cells counterintuitively decreased with age. Furthermore, we found a concerted age-associated increase in type 2/interleukin (IL)4-expressing memory subpopulations across CD4+ and CD8+ T cell compartments (CCR4+CD8+ Tcm and Th2 CD4+ Tmem), suggesting a systematic functional shift in immune homeostasis with age. Our work provides novel insights into healthy human aging and a comprehensive annotated resource.

Mucosal-Associated Invariant T (MAIT) cells are T cells with a semi-invariant T cell receptor (TCR), recognizing riboflavin precursors presented by a non-polymorphic MR1 molecule. As these precursors are produced by the gut microbiome, we characterized the frequency, phenotype and clonality of MAIT cells in human colons with and without Crohn's disease (CD).

The transcriptome of MAIT cells sorted from blood and intestinal lamina propria cells from colectomy recipients were compared with other CD8+ T cells. Colon biopsies from an additional ten CD patients and ten healthy controls (HC) were analyzed by flow cytometry. TCR genes were sequenced from individual MAIT cells from these biopsies and compared with those of MAIT cells from autologous blood.

MAIT cells in the blood and colon showed a transcriptome distinct from other CD8 T cells, with more expression of the IL-23 receptor. MAIT cells were enriched in the colons of CD patients, with less NKG2D in inflamed versus uninflamed segments. Regardless of disease, most MAIT cells expressed integrin α4β7 in the colon but not in the blood, where they were enriched for α4β7 expression. TCR sequencing revealed heterogeneity in the colon and blood, with few public sequences associated with cohorts.

MAIT cells are enriched in the colons of CD patients and disproportionately express molecules (IL-23R, integrin α4β7) targeted by CD therapeutics, to suggest a pathogenic role for them in CD. Public TCR sequences were neither common nor sufficiently restricted to a cohort to suggest protective or pathogenic antigen-specificities.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused millions of COVID-19 cases and deaths worldwide. Severity of pulmonary pathologies and poor prognosis were reported to be associated with the activation non-virus-specific bystander T cells. In addition, high concentrations of the macrophage migration inhibitory factor (MIF) were found in serum of COVID-19 patients. We hypothesized that these two pathogenic factors might be related and analyzed the expression of receptors for MIF on T cells in COVID-19. T cells from PBMCs of hospitalized patients with mild and severe COVID-19 were characterized. A significantly higher proportion of CD4+ and CD8+ T cells from COVID-19 patients expressed CD74 on the cell surface compared to healthy controls. To induce intracellular signaling upon MIF binding, CD74 forms complexes with CD44, CXCR2, or CXCR4. The vast majority of CD74+ T cells expressed CD44, whereas expression of CXCR2 and CXCR4 was low in controls but increased upon SARS-CoV-2 infection. Hence, T cells in COVID-19 patients express receptors that render them responsive to MIF. A detailed analysis of CD74+ T cell populations revealed that most of them had a central memory phenotype early in infection, while cells with an effector and effector memory phenotype arose later during infection. Furthermore, CD74+ T cells produced more cytotoxic molecules and proliferation markers. Our data provide new insights into the MIF receptor and co-receptor repertoire of bystander T cells in COVID-19 and uncovers a novel and potentially druggable aspect of the immunological footprint of SARS-CoV-2.

Cytolytic CD8+ T cells mediate immunopathology in cutaneous leishmaniasis without controlling parasites. Here, we identify factors involved in CD8+ T cell migration to the lesion that could be targeted to ameliorate disease severity. CCR5 was the most highly expressed chemokine receptor in patient lesions, and the high expression of CCL3 and CCL4, CCR5 ligands, was associated with delayed healing of lesions. To test the requirement for CCR5, Leishmania-infected Rag1-/- mice were reconstituted with CCR5-/- CD8+ T cells. We found that these mice developed smaller lesions accompanied by a reduction in CD8+ T cell numbers compared to controls. We confirmed these findings by showing that the inhibition of CCR5 with maraviroc, a selective inhibitor of CCR5, reduced lesion development without affecting the parasite burden. Together, these results reveal that CD8+ T cells migrate to leishmanial lesions in a CCR5-dependent manner and that blocking CCR5 prevents CD8+ T cell-mediated pathology.

Hepatitis A is a vaccine-preventable infection caused by the hepatitis A virus (HAV). Over 150 million new infections of hepatitis A occur annually. HAV causes an acute inflammatory reaction in the liver that usually resolves spontaneously without chronic sequelae. However, up to 20% of patients experience a prolonged or relapsed course and <1% experience acute liver failure. Host factors, such as immunological status, age, pregnancy and underlying hepatic diseases, can affect the severity of disease. Anti-HAV IgG antibodies produced in response to HAV infection persist for life and protect against re-infection; vaccine-induced antibodies against hepatitis A confer long-term protection. The WHO recommends vaccination for individuals at higher risk of infection and/or severe disease in countries with very low and low hepatitis A virus endemicity, and universal childhood vaccination in intermediate endemicity countries. To date, >25 countries worldwide have implemented such programmes, resulting in a reduction in the incidence of HAV infection. Improving hygiene and sanitation, rapid identification of outbreaks and fast and accurate intervention in outbreak control are essential to reducing HAV transmission.

Bystander activation of memory T cells occurs via cytokine signaling alone in the absence of T cell receptor (TCR) signaling and provides a means of amplifying T cell effector responses in an antigen-nonspecific manner. While the role of Programmed Cell Death Protein 1 (PD-1) on antigen-specific T cell responses is extensively characterized, its role in bystander T cell responses is less clear. We examined the role of the PD-1 pathway during human and mouse non-antigen-specific memory T cell bystander activation and observed that PD-1+ T cells demonstrated less activation and proliferation than activated PD-1- populations in vitro. Higher activation and proliferative responses were also observed in the PD-1- memory population in both mice and patients with cancer receiving high-dose IL-2, mirroring the in vitro phenotypes. This inhibitory effect of PD-1 could be reversed by PD-1 blockade in vivo or observed using memory T cells from PD-1-/- mice. Interestingly, increased activation through abrogation of PD-1 signaling in bystander-activated T cells also resulted in increased apoptosis due to activation-induced cell death (AICD) and eventual T cell loss in vivo. These results demonstrate that the PD-1/PD-Ligand 1 (PD-L1) pathway inhibited bystander-activated memory T cell responses but also protected cells from AICD.

Immunosenescence and exhaustion are involved in the development and progression of type 2 diabetes (T2D) and metabolic liver diseases, including fatty liver, fibrosis, and cirrhosis, in humans. However, the relationships of the senescence and exhaustion of T cells with insulin resistance-associated liver diseases remain incompletely understood. To better define the relationship of T2D with nonalcoholic fatty liver disease, 59 patients (mean age 58.7 ± 11.0 years; 47.5% male) with T2D were studied. To characterize their systemic immunophenotypes, peripheral blood mononuclear cells were analyzed using flow cytometry. Magnetic resonance imaging (MRI)-based proton density fat fraction and MRI-based elastography were performed using an open-bore, vertical-field 3.0 T scanner to quantify liver fat and fibrosis, respectively. The participants with insulin resistance had a significantly larger population of CD28 - CD57+ senescent T cells among the CD4+ and CD8 + T cells than those with lower Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) values. The abundances of senescent CD4+ and CD8 + T cells and the HOMA-IR positively correlated with the severity of liver fibrosis, assessed using MRI-based elastography. Interleukin 15 from hepatic monocytes was found to be an inducer of bystander activation of T cells, which is associated with progression of liver disease in the participants with T2D. Furthermore, high expression of genes related to senescence and exhaustion was identified in CD4+ and CD8 + T cells from the participants with nonalcoholic steatohepatitis or liver cirrhosis. Finally, we have also demonstrated that hepatic T-cell senescence and exhaustion are induced in a diet or chemical-induced mouse model with nonalcoholic steatohepatitis. In conclusion, we have shown that T-cell senescence is associated with insulin resistance and metabolic liver disease in patients with T2D.

Hepatitis A virus (HAV) infections are considered not to trigger innate immunity in vivo, in contrast to hepatitis C virus (HCV). This lack of induction has been imputed to strong interference by HAV proteases 3CD and 3ABC. We aimed to elucidate the mechanisms of immune activation and counteraction by HAV and HCV in vivo and in vitro.

Albumin-urokinase-type plasminogen activator/severe combined immunodeficiency (Alb/uPA-SCID) mice with humanised livers were infected with HAV and HCV. Hepatic cell culture models were used to assess HAV and HCV sensing by Toll-like receptor 3 and retinoic acid-inducible gene I/melanoma differentiation-associated protein 5 (RIG-I/MDA5), respectively. Cleavage of the adaptor proteins TIR-domain-containing adapter-inducing interferon-β (TRIF) and mitochondrial antiviral-signalling protein (MAVS) was analysed by transient and stable expression of HAV and HCV proteases and virus infection.

We detected similar levels of interferon-stimulated gene induction in hepatocytes of HAV- and HCV-infected mice with humanised liver. In cell culture, HAV induced interferon-stimulated genes exclusively upon MDA5 sensing and depended on LGP2 (laboratory of genetics and physiology 2). TRIF and MAVS were only partially cleaved by HAV 3ABC and 3CD, not sufficiently to abrogate signalling. In contrast, HCV NS3-4A efficiently degraded MAVS, as previously reported, whereas TRIF cleavage was not detected.

HAV induces an innate immune response in hepatocytes via MDA5/LGP2, with limited control of both pathways by proteolytic cleavage. HCV activates Toll-like receptor 3 and lacks TRIF cleavage, suggesting that this pathway mainly contributes to HCV-induced antiviral responses in hepatocytes. Our results shed new light on the induction of innate immunity and counteraction by HAV and HCV.

Understanding the mechanisms that determine the differential outcomes of HAV and HCV infections is crucial for the development of effective therapies. Our study provides insights into the interplay between these viruses and the host innate immune response in vitro and in vivo, shedding light on previously controversial or only partially investigated aspects. This knowledge could tailor the development of new strategies to combat HCV persistence, as well as improve our understanding of the factors underlying successful HAV clearance.

Both acute and chronic hepatitis C virus (HCV) infections are characterized by inflammation. HCV and reduced liver blood filtration contribute to inflammation; however, the mechanisms of systemic immune activation and dysfunction as a result of HCV infection are not clear. We measured circulating inflammatory mediators (IL-6, IP10, sCD163, sCD14), indices of endotoxemia (EndoCab, LBP, FABP), and T cell markers of exhaustion and senescence (PD-1, TIGIT, CD57, KLRG-1) in HCV-infected participants, and followed a small cohort after direct-acting anti-viral therapy. IL-6, IP10, Endocab, LBP, and FABP were elevated in HCV participants, as were T cell co-expression of exhaustion and senescence markers. We found positive associations between IL-6, IP10, EndoCab, LBP, and co-expression of T cell markers of exhaustion and senescence. We also found numerous associations between reduced liver function, as measured by plasma albumin levels, and T cell exhaustion/senescence, inflammation, and endotoxemia. We found positive associations between liver stiffness (TE score) and plasma levels of IL-6, IP10, and LBP. Lastly, plasma IP10 and the proportion of CD8 T cells co-expressing PD-1 and CD57 decreased after initiation of direct-acting anti-viral therapy. Although associations do not prove causality, our results support the model that translocation of microbial products, resulting from decreased liver blood filtration, during HCV infection drives chronic inflammation that results in T cell exhaustion/senescence and contributes to systemic immune dysfunction.