Immunoregulation in larval Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis)

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

FGL2-wired macrophages secrete CXCL7 to regulate the stem-like functionality of glioma cells

Glioma stem cells (GSCs) are thought to underlie glioma initiation, evolution, resistance to therapies, and relapse. They are defined by their capacity to initiate glioma in immunocompromised mice which precludes analysis of their interaction with immune cells. Macrophages dominate the immune cell composition in glioma. We hypothesized that stemness and immune evasion induced by macrophages are closed intertwined in glioma. By using mass cytometry and RNA sequencing, we reveal that in immunocompetent mice, FGL2 promotes the stem-like phenotypes of glioma cells in an expression level-dependent manner. Mechanistically, FGL2-producing glioma cells recruit macrophages into the tumor microenvironment and induce the macrophages to secrete CXCL7 via the CD16/SyK/PI3K/HIF1α pathways. CXCL7, in turn, enhances the stem-like functionality of glioma cells, resulting in an increase in tumor incidence and progression that can be blocked with a neutralizing anti-CXCL7 antibody. Clinically, the FGL2-CXCL7 paracrine loop positively correlated with a higher macrophage signature and poorer prognosis in glioma patients. Thus, glioma cells' stem-like functionality is regulated by FGL2 in the presence of macrophages, and the FGL2-CXCL7 paracrine signaling axis is critical for regulating this function.

Tumor-associated macrophage polarization promotes the progression of esophageal carcinoma

The immune response facilitated by tumor-associated macrophages is a vital determinant of tumor progression. We identified differentially expressed genes between various macrophage phenotypes in the Gene Expression Omnibus, and used Kaplan-Meier Plotter to determine which of them altered the prognosis of esophageal carcinoma patients. Fibrinogen-like protein 2 (FGL2), an immunosuppressive factor in the tumor microenvironment of various cancers, was upregulated in M2 macrophages, and higher FGL2 expression was associated with poorer survival in esophageal carcinoma patients. Using the TIMER database, we found that FGL2 expression correlated positively with the levels of immune markers of infiltrating B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils and dendritic cells in esophageal carcinoma samples. Correlation analyses in cBioPortal revealed that the mRNA levels of FGL2 correlated strongly with those of interleukin 10, matrix metalloproteinase 9, C-C motif chemokine ligand 5, T-cell immunoglobulin mucin 3, interleukin 13, vascular cell adhesion molecule 1, macrophage colony-stimulating factor and fibroblast growth factor 7 in esophageal carcinoma tissues. The same cytokines were upregulated when esophageal squamous cell carcinoma cells were co-cultured with M2-like tumor-associated macrophages. Thus, by secreting FGL2, M2-like tumor-associated macrophages may create an immunosuppressive tumor microenvironment that induces the occurrence and progression of esophageal carcinoma.

Expression of B and T lymphocyte attenuator (BTLA) in macrophages contributes to the fulminant hepatitis caused by murine hepatitis virus strain-3

OBJECTIVES

Fulminant viral hepatitis (FH) remains a serious clinical problem for which the underlying pathogenesis remains unclear. The B and T lymphocyte attenuator (BTLA) is an immunoglobulin-domain-containing protein that has the capacity to maintain peripheral tolerance and limit immunopathological damage during immune responses. However, its precise role in FH has yet to be investigated.

DESIGN

BTLA-deficient (BTLA-/-) mice and their wild-type littermates were infected with murine hepatitis virus strain-3 (MHV-3), and the levels of tissue damage, cell apoptosis, serum liver enzymes, fibrinogen-like protein 2 (FGL2) and cytokine production were measured and compared. Survival rate was studied after MHV-3 infection with or without adoptive transferring macrophages.

RESULTS

FGL2 production, liver and spleen damage, and mortality were significantly reduced in BTLA-/- mice infected with MHV-3. This effect is due to rapid, TRAIL (TNF-related apoptosis-inducing ligand)-dependent apoptosis of MHV-3-infected macrophages in BTLA-/- mice. The early loss of macrophages resulted in reduced pathogenic tumour necrosis factor α (TNFα) and FGL2 levels and lower viral titres. The importance of TNFα in MHV-3-induced pathology was demonstrated by increased mortality in TNFα-treated MHV-3-infected BTLA-/- mice, whereas TNFα-/- mice were resistant to the infection. Moreover, adoptively transferring macrophages to BTLA-/- mice caused sensitisation, whereas blocking BTLA protected wild-type mice from virus-induced FH mortality.

CONCLUSIONS

BTLA promotes the pathogenesis of virus-induced FH by enhancing macrophage viability and function. Targeting BTLA may be a novel strategy for the treatment of FH.

The Role of FGL2 in the Pathogenesis and Treatment of Hepatitis C Virus Infection

Chronic hepatitis C virus (HCV) infection is a leading cause of liver disease worldwide and remains the most common indication for liver transplantation. The current standard of care leads to a sustained viral response of roughly 50% of treated patients at best. Furthermore, anti-viral therapy is expensive, prolonged, and associated with serious side-effects. Evidence suggests that a poor response to treatment may be the result of a suppressed anti-viral immunity due to the presence of increased numbers and activity of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg cells). We and others have recently identified fibrinogen-like protein 2 (FGL2) as a putative effector of Treg cells, which accounts for their suppressive function through binding to Fc gamma receptors (FcγR). In an experimental model of fulminant viral hepatitis, our laboratory showed that increased plasma levels of FGL2 pre- and post-viral infection were predictive of susceptibility and severity of disease. Moreover, treatment with antibody to FGL2 fully protected susceptible animals from the lethality of the virus, and adoptive transfer of wild-type Treg cells into resistant fgl2-deficient animals accelerated their mortality post-infection. In patients with HCV infection, plasma levels of FGL2 and expression of FGL2 in the liver correlated with the course and severity of the disease. Collectively, these studies suggest that FGL2 may be used as a biomarker to predict disease progression in HCV patients and be a logical target for the development of novel therapeutic approaches for the treatment of patients with HCV infection.

Tumor necrosis factor α (TNF-α) receptor-I is required for TNF-α-mediated fulminant virus hepatitis caused by murine hepatitis virus strain-3 infection

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TNFR1^−/− mice displayed a dramatic decrease in tissue necrosis and cell apoptosis in the MHV-3 infected spleens and livers.

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TNFR1 deficiency directly impeded FGL2 secretion as well as reduced Fas and FasL expression in MHV-3 infected livers.

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TNFR1 deficiency impeded neutrophils, which produce proinflammatory factors and FGL2 directly, infiltration into liver and spleen.

TNF-α plays an essential role in the pathogenesis of fulminant virus hepatitis (FH) caused by infection with murine hepatitis virus strain-3 (MHV-3). However, the specific TNF-α receptors (TNFR) involved in this disease and how they mediate this effect are uncertain. Here, we showed that the expression of TNFR1 and TNFR2 in the liver and spleen was triggered by MHV-3. However, only TNFR1^−/− mice were resistant to MHV-3 mediated FH, as displayed by a dramatic decrease in tissue necrosis and cell apoptosis in the infected spleens and livers from TNFR1^−/− mice, as well as prolonged survival in these mice compared to wild type littermate controls. Mechanistically, TNFR1 deficiency directly impeded the serum and tissue levels of fibrinogen-like protein 2 (FGL2), a virus-induced procoagulant molecule that promotes cell apoptosis. Additionally, the expression of apoptosis-associated molecules, Fas and Fas ligand (FasL) in the infected organs from TNFR1^−/− mice were also decreased. Moreover, the infiltration of neutrophils rather than Foxp3⁺ regulatory T cells, which produce proinflammatory factors and FGL2 directly, into the infected liver and spleen tissues was also decreased in TNFR1^−/− mice. These combined results indicate that signaling through TNFR1 plays an essential role in the pathogenesis of FH caused by MHV-3 infection, and interruption of this signaling pathway could be useful for clinical therapy.

mRNA/lncRNA expression patterns and the function of fibrinogen-like protein 2 in Meishan pig endometrium during the preimplantation phases

Embryonic implantation involves a complex and well-coordinated interaction between the developing conceptus and maternal uterus, and the preimplantation period has a major impact on litter size in pigs. The present study aimed to investigate the vital messenger RNAs (mRNAs) and long noncoding RNAs (lncRNAs) that regulate preimplantation in Meishan pigs. The enriched Gene Ontology terms were all related to "binding." Furthermore, "ECM-receptor interaction" was predicted as an important pathway that regulated the success of implantation. We speculated that the differentially expressed mRNAs S100A9, ANXA8, MUC16, and FGL2 and the differentially expressed lncRNAs TCONS_11206566, TCONS_09904861, and TCONS_1252933 may play vital roles in the process of implantation. Furthermore, this study verified that FGL2 was highly expressed on Day 12 of pregnancy, and we also investigated the function of FGL2 during preimplantation in vivo. In conclusion, this study provides useful information for further analyses of the molecular mechanisms of implantation in Chinese domestic pigs.

The imitation switch ATPase Snf2l is required for superovulation and regulates Fgl2 in differentiating mouse granulosa cells

Imitation switch (ISWI) proteins are catalytic subunits of chromatin remodeling complexes that alter nucleosome positioning by hydrolyzing ATP to regulate access to DNA. In mice, there are two paralogs, SNF2-homolog (SNF2H) and SNF2-like (SNF2L), which participate in different complexes and have contrasting patterns of expression. Here we investigate the role of SNF2L in ovaries by characterizing a mouse bearing an inactivating deletion of exon 6 that disrupts the ATPase domain. Snf2l mutant mice produce significantly fewer eggs than control mice when superovulated. Gonadotropin stimulation leads to a significant deficit in secondary follicles and an increase in abnormal antral follicles. Mutant females also failed to induce fibrinogen-like 2 (Fgl2) in response to human chorionic gonadotropin (hCG) stimulation, while overexpression of SNF2L was sufficient to drive its expression in granulosa cells. SNF2L was also shown to directly interact with the nuclear receptor co-activator flightless I (FLI-I) as shown by immunoprecipitation. These results begin to establish a role for SNF2L in the precise coordination of gene expression in granulosa cells during folliculogenesis and its broader implications in fertility.

Fibrinogen-like protein 2 in inflammatory diseases: A future therapeutic target

Fibrinogen-like protein 2 (FGL2), a member of the fibrinogen family, exists as a membrane-bound protein with immune-associated coagulation activity and a soluble form possessing immunosuppressive functions. The immunomodulatory role of FGL2 is evident in fibrin deposition-associated inflammatory diseases and cancer, suggesting that FGL2 expression could be exploited as a disease biomarker and a therapeutic target. Recently, in vitro studies and knockout and transgenic animal FGL2 models have been used by us and others to reveal the involvement of FGL2 in the pathogenesis of various inflammatory diseases. This review summarizes our current knowledge of the immunomodulatory role of FGL2 in inflammatory diseases and examines the role of FGL2 as a potential therapeutic target.

FGL2 is positively correlated with enhanced antitumor responses mediated by T cells in lung adenocarcinoma

Lung cancer is the most common malignant tumor, accounting for 25% of cancer-related deaths and 14% of new cancers worldwide. Lung adenocarcinoma is the most common type of pulmonary cancer. Although there have been some improvements in the traditional therapy of lung cancer, the outcome and prognosis of patients remain poor. Lung cancer is the leading cause of cancer-related deaths worldwide, with 1.8 million new cases being diagnosed each year. Precision medicine based on genetic alterations is considered a new strategy of lung cancer treatment that requires highly specific biomarkers for precision diagnosis and treatment. Fibrinogen-like protein 2 (FGL2) plays important roles in both innate and adaptive immunity. However, the diagnostic value of FGL2 in lung cancer is largely unknown. In this study, we systematically investigated the expression profile and potential functions of FGL2 in lung adenocarcinoma. We used the TCGA and Oncomine datasets to compare the FGL2 expression levels between lung adenocarcinoma and adjacent normal tissues. We utilized the GEPIA, PrognoScan and Kaplan-Meier plotter databases to analyze the relationship between FGL2 expression and the survival of lung adenocarcinoma patients. Then, we investigated the potential roles of FGL2 in lung adenocarcinoma with the TIMER database and functional enrichment analyses. We found that FGL2 expression was significantly lower in lung adenocarcinoma tissue compared with adjacent normal tissue. A high expression level of FGL2 was correlated with better prognostic outcomes of lung adenocarcinoma patients, including overall survival and progression-free survival. FGL2 was positively correlated with the infiltration of immune cells, including dendritic cells, CD8+ T cells, macrophages, B cells, and CD4+ T cells, in lung adenocarcinoma. Functional enrichment analyses also showed that a high expression level of FGL2 was positively correlated with enhanced T cell activities, especially CD8+ T cell activation. Thus, we propose that high FGL2 expression, which is positively associated with enhanced antitumor activities mediated by T cells, is a beneficial marker for lung adenocarcinoma treatment outcomes.

IL-33 protects murine viral fulminant hepatitis by targeting coagulation hallmark protein FGL2/fibroleukin expression

Fulminant hepatitis (FH) is characterized by rapid liver failure and high mortality. The pathogenesis of viral FH includes virus-induced immune activation, inflammation, and subsequent hepatic apoptosis and necrosis. However, the mechanisms that underlie FH progression are unclear. IL-33 is a member of the IL-1-related cytokines, considered to be an "alarmin" that participates in various diseases, but its precise role in the coagulation of FH is not very clear. In our study, we found that IL-33 is significantly elevated in mice infected with murine hepatitis virus strain 3 (MHV-3). This is accompanied by an increase in pro-coagulant fibrinogen-like protein 2 (FGL2) in the liver. Previous studies have suggested that an increase in FGL2 is diagnostic of FH and liver necrosis, and animals with no FGL2 had better survivorship during FH. Our studies showed that IL-33 administration in a MHV-3 infection promoted survival during FH, with a significant reduction in FGL2 expression and liver inflammation. In vitro IL-33 treatment abrogated MHV-3 and IFN-γ induced FGL2 expression in RAW264.7 and THP-1 cells, respectively. In conclusion, our research suggests that IL-33 protects against viral fulminant hepatitis in mice by antagonizing expression of the pro-coagulant protein FGL2.

miR-146b suppresses LPS-induced M1 macrophage polarization via inhibiting the FGL2-activated NF-κB/MAPK signaling pathway in inflammatory bowel disease

OBJECTIVES

M1 macrophage polarization and phenotype in Inflammatory Bowel Disease (IBD) are common biological responses.

METHOD

Herein, IBD mice models were constructed and macrophages were derived.

RESULTS

It was discovered that microRNA-146b (miR-146b) was downregulated in IBD mice and Lipopolysaccharide (LPS)-induced macrophages. Moreover, the inhibitory role of overexpressed miR-146b in reducing the inflammation level and blocking M1 macrophage polarization was confirmed. Further investigation indicated that Fibrinogen Like 2 (FGL2) acted as the target gene of miR-146b, and FGL2 mediated activation of NLRP3, NF-κB-p65, and p38-MAPK. More importantly, it was validated that miR-146b could ameliorate inflammatory phenotype and prevent M1 macrophage polarization via inhibiting FGL2 in vitro, and miR-146b overexpression alleviated the intestinal injury of IBD mice in vivo.

CONCLUSIONS

Overall, it is potential to use miR-146b for the amelioration of IBD.

Identification of integrative molecular and clinical profiles of Fibrinogen-like protein 2 in gliomas using 1323 samples

BACKGROUND

Fibrinogen-like protein 2 (FGL2), a member of the fibrinogen superfamily, has been described to augment immunosuppression in gliomas. However, the precise clinical molecular features and the prognostic relevance of FGL2 in gliomas remain unclear. Therefore, a comprehensive analysis of the role of FGL2 in gliomas would provide insights into the therapeutic implications for this disease.

METHODS

Totally, 1323 glioma samples with RNA-seq and microarray data from TCGA and CGGA databases were used to clarify the clinical significance and molecular profile of FGL2 in glioma. The findings were further validated through immunohistochemistry (IHC).

RESULTS

The transcriptional level of FGL2 was positively associated with tumor grade in gliomas, which was confirmed at the protein level through IHC staining. Consistently, FGL2 was significantly enriched in isocitrate dehydrogenase wild-type tumors and the mesenchymal subtype of gliomas. We also demonstrated FGL2 expression correlated with high immune scores and infiltration of immune cell populations, including T cells, macrophages and B cells. Pearson's correlation analysis revealed that FGL2-related genes correlated with inflammatory-immune responses, particularly T cell-mediated immune response. Additionally, FGL2 expression was found tightly associated with immune checkpoints PD-L1 and PD-L2. Clinically, patients with high FGL2 expression exhibited unfavorable overall survival.

CONCLUSION

Our results provide the integrative molecular and clinical profiles of FGL2 in gliomas and emphasize the importance of prospective studies on the FGL2-related immune-inflammatory network.

Prognostic significance and gene co-expression network of CD16A and FGL2 in gliomas

Introduction

The CD16A protein encoding gene FcγRIIIa (FCGR3A) and its potential ligand Fibrinogen-like protein 2 (FGL2) are involved in various cell physiological activities on the extracellular surface. Aberrant expression of these genes has been linked to tumorigenesis.

Methods

To assess the prognostic significance of FCGR3A and FGL2 transcription expression in glioma and explore their roles in glioma initiation and progression, we utilized multiple online databases, including TCGA, GEPIA, CGGA, cBioPortal, TISCH, LinkedOmics, Ivy Glioblastoma Atlas Project, and Human Protein Atlas.

Results

Our analysis revealed that FCGR3A and FGL2 expression was significantly correlated with clinical variables such as age, tumor type, WHO grade, histology, IDH-1 mutation, and 1p19q status. A strong correlation was also observed between the transcriptional expression levels of FCGR3A and FGL2. High expression of both genes predicted poor prognosis in primary and recurrent glioma patients, particularly those with lower grade gliomas. Cox regression analysis further confirmed that elevated expression of FCGR3A and FGL2 were independent prognostic factors for shorter overall survival in glioma patients. Gene co-expression network analysis suggested that FCGR3A, FGL2, and their co-expressed genes were involved in inflammatory activities and tumor-related signaling pathways. Additionally, tissue microarrays from glioma patients at Tiantan Hospital showed significantly higher FCGR3A protein expression in high-grade gliomas compared to low-grade gliomas.

Discussion

In conclusion, our findings suggest that FCGR3A and FGL2 could serve as promising prognostic biomarkers and potential therapeutic targets for glioma patients.

FGL1 and FGL2: emerging regulators of liver health and disease

Liver disease is a complex group of diseases with high morbidity and mortality rates, emerging as a major global health concern. Recent studies have highlighted the involvement of fibrinogen-like proteins, specifically fibrinogen-like protein 1 (FGL1) and fibrinogen-like protein 2 (FGL2), in the regulation of various liver diseases. FGL1 plays a crucial role in promoting hepatocyte growth, regulating lipid metabolism, and influencing the tumor microenvironment (TME), contributing significantly to liver repair, non-alcoholic fatty liver disease (NAFLD), and liver cancer. On the other hand, FGL2 is a multifunctional protein known for its role in modulating prothrombin activity and inducing immune tolerance, impacting viral hepatitis, liver fibrosis, hepatocellular carcinoma (HCC), and liver transplantation. Understanding the functions and mechanisms of fibrinogen-like proteins is essential for the development of effective therapeutic approaches for liver diseases. Additionally, FGL1 has demonstrated potential as a disease biomarker in radiation and drug-induced liver injury as well as HCC, while FGL2 shows promise as a biomarker in viral hepatitis and liver transplantation. The expression levels of these molecules offer exciting prospects for disease assessment. This review provides an overview of the structure and roles of FGL1 and FGL2 in different liver conditions, emphasizing the intricate molecular regulatory processes and advancements in targeted therapies. Furthermore, it explores the potential benefits and challenges of targeting FGL1 and FGL2 for liver disease treatment and the prospects of fibrinogen-like proteins as biomarkers for liver disease, offering insights for future research in this field.

Assessment of Fibrinogen-like 2 (FGL2) in Human Chronic Kidney Disease through Transcriptomics Data Analysis

Fibrinogen-like 2 (FGL2) was recently found to be associated with fibrosis in a mouse model of kidney damage and was proposed as a potential therapeutic target in chronic kidney disease (CKD). We assessed the association of renal FGL2 mRNA expression with the disease outcome in two independent CKD cohorts (NEPTUNE and Innsbruck CKD cohort) using Kaplan Meier survival analysis. The regulation of FGL2 in kidney biopsies of CKD patients as compared to healthy controls was further assessed in 13 human CKD transcriptomics datasets. The FGL2 protein expression in human renal tissue sections was determined via immunohistochemistry. The regulators of FGL2 mRNA expression in renal tissue were identified in the co-expression and upstream regulator analysis of FGL2-positive renal cells via the use of single-cell RNA sequencing data from the kidney precision medicine project (KPMP). Higher renal FGL2 mRNA expression was positively associated with kidney fibrosis and negatively associated with eGFR. Renal FGL2 mRNA expression was upregulated in CKD as compared with healthy controls and associated with CKD progression in the Innsbruck CKD cohort (p-value = 0.0036) and NEPTUNE cohort (p-value = 0.0048). The highest abundance of FGL2 protein in renal tissue was detected in the thick ascending limb of the loop of Henle and macula densa, proximal tubular cells, as well as in glomerular endothelial cells. The upstream regulator analysis identified TNF, IL1B, IFNG, NFKB1, and SP1 as factors potentially inducing FGL2-co-expressed genes, whereas factors counterbalancing FGL2-co-expressed genes included GLI1, HNF1B, or PPARGC1A. In conclusion, renal FGL2 mRNA expression is elevated in human CKD, and higher FGL2 levels are associated with fibrosis and worse outcomes.

A homozygous truncating mutation of FGL2 is associated with immune dysregulation

BACKGROUND

The type II transmembrane protein fibrinogen-like protein 2 (FGL2) plays critical roles in hemostasis and immune regulation. The C-terminal immunoregulatory domain of FGL2 can be secreted and is a mediator of regulatory T (Treg) cell suppression. Fgl2^-/- mice develop autoantibodies and glomerulonephritis and have impaired Treg cell function.

OBJECTIVE

Our aim was to identify the genetic underpinning and immune function in a patient with childhood onset of leukocytoclastic vasculitis, systemic inflammation, and autoantibodies.

METHODS

Whole-exome sequencing was performed on patient genomic DNA. FGL2 protein expression was examined in HEK293 transfected cells by immunoblotting and in PBMCs by flow cytometry. T follicular helper cells and Treg cells were examined by flow cytometry. Treg cell suppression of T-cell proliferation was assessed in vitro.

RESULTS

The patient had a homozygous mutation in FGL2 (c.614_617del:p.V205fs), which led to the expression of a truncated FGL2 protein that preserves the N-terminal domain but lacks the C-terminal immunoregulatory domain. The patient had an increased percentage of circulating T follicular helper and Treg cells. The patient's Treg cells had impaired in vitro suppressive ability that was rescued by the addition of full-length FGL2. Unlike full-length FGL2, the truncated FGL2^V205fs mutant failed to suppress T-cell proliferation.

CONCLUSIONS

We identified a homozygous mutation in FGL2 in a patient with immune dysregulation and impaired Treg cell function. Soluble FGL2 rescued the Treg cell defect, suggesting that it may provide a useful therapy for the patient.

Proteinase-activated receptor-1 antagonist attenuates brain injury via regulation of FGL2 and TLR4 after intracerebral hemorrhage in mice

Proteinase-activated receptor-1 (PAR1) antagonist plays a protective effect in brain injury. We investigated the potential function and mechanisms of PAR1 antagonist in ICH-induced brain injury. Results showed that PAR1 antagonist protected against neurobehavior deficits, brain edema and BBB integrity in ICH mice via activating JNK/ERK/p38 MAPK signaling pathway at 24h after ICH. In addition, ICH resulted in the increase of FGL2 and TLR4 expression over time, and phosphorylated JNK, ERK and p38 MAPK expression. Suppression of FGL2 and TLR4 alleviated brain injury and decreased the expression of p-JNK, p-ERK, p-p38 MAPK and p-IKKα at 24 h after ICH; while overexpression of them showed the opposite result. Moreover, the protective effect of PAR1 antagonist on ICH-induced brain injury was blocked by FGL2 or TLR4 overexpression, and the levels of p-JNK, p-ERK and p-p38 MAPK were inhibited. Furthermore, PAR1 antagonist combined with TLR4 antagonist markedly alleviated brain injury after ICH at 72h. Overall, PAR1 antagonist protected against short-term brain injury, and the effect of PAR1 antagonist on ICH-induced brain injury was mediated by FGL2 or TLR4.

DIA-based quantitative proteomic analysis of porcine endometrium in the peri-implantation phase

The 12th day of gestation is a critical period for embryo loss and the beginning of imminent implantation in sows. Data independent acquisition (DIA) technology is one of the high-throughput, high-resolution and reproducible proteomics technologies for large-scale digital qualitative and quantitative research. The aim of this study was to identify and characterize the protein abundance landscape of Yorkshire pig endometrium on the 12th day of pregnancy (P12) and estrous cycle (C12) using DIA proteomics. A total of 1251 differentially abundant proteins (DAPs) were identified, of which 882 were up-regulated and 369 were down-regulated at P12. Functional enrichment analysis showed that the identified proteins were related to metabolism, biosynthesis and signaling pathways. Three proteins were selected for Western blot (WB) validation and the results were consistent with the DIA data. Further combined with transcriptome data, fibrinogen like 2 (FGL2) and S100 calcium binding protein A8 (S100A8) were verified to be highly abundant in the P12 endometrial epithelium. In summary, there were significantly different abundance of proteome profiles in C12 and P12 endometrium, suggesting that DAPs are associated with changes in endometrial receptivity, which laid the foundation for further research on related regulatory mechanisms. SIGNIFICANCE: The 12th day of gestation is an important point in the peri-implantation period of pigs, when the endometrium presents a receptive state under the stimulation of estrogen. DIA proteomics technology is an emerging protein identification technology in recent years, which can obtain protein information through comprehensive and unbiased scanning. In this study, DIA technology was used to characterize endometrial proteins in pigs during the peri-implantation period. The results showed that higher protein abundance was detected using the DIA technique, and some of these DAPs may be involved in regulating embryo implantation. This study will help to better reveal the related proteins involved in embryo implantation, and lay a foundation for further research on the mechanism of endometrial regulation of embryo implantation. SIGNIFICANCE OF THE STUDY: The 12th day of gestation is an important point in the peri-implantation period of pigs, when the endometrium presents a receptive state under the stimulation of estrogen. DIA proteomics technology is an emerging protein identification technology in recent years, which can obtain protein information through comprehensive and unbiased scanning. In this study, DIA technology was used to characterize endometrial proteins in pigs during the peri-implantation period. The results showed that higher protein abundance was detected using the DIA technique, and some of these DAPs may be involved in regulating embryo implantation. This study will help to better reveal the related proteins involved in embryo implantation, and lay a foundation for further research on the mechanism of endometrial regulation of embryo implantation.

Fibrinogen-like 2 in tumor-associated macrophage-derived extracellular vesicles shapes an immunosuppressive microenvironment in colorectal liver metastases by promoting tumor stemness and neutrophil extracellular traps formation

Investigating the mechanisms underlying the development of an immunosuppressive microenvironment within colorectal liver metastases (CRLM) is important for identifying synergistic targets for immunotherapy. The regulatory role of tumor-associated macrophage-derived extracellular vesicles (TAM-EVs) in the immune microenvironment of CRLM has not yet been fully explored. Here, we found that TAM-EVs shaped the immunosuppressive microenvironment at the invasive front in murine CRLM models, thus dampening anti-PD-1 immunotherapy. This environment is characterized by an increased tumor stemness potential and abundant neutrophil extracellular traps (NETs) formation. Mechanistically, TAM-EVs-derived fibrinogen-like 2 (FGL2) interacts with the FCGR2B receptor in tumor cells, which further activates a p-STAT3/IL-1β positive feedback loop to increase the stemness potential of cancer cells, whereas IL-1β mediates the communication between cancer cells and neutrophils. The use of an anti-IL-1β monoclonal antibody can reduce NETs production and synergize with anti-PD-1 immunotherapy, which offers clinical translational significance for CRLM therapy. The FGL2/p-STAT3/IL-1β loop correlates with an immunosuppressive microenvironment and poor prognosis in human patients with CRLM. Our results revealed the potential of enhancing the efficacy of immunotherapy via the targeted clearance of NETs using anti-IL-1β monoclonal antibodies, which have significant clinical translational value in the treatment of CRLM.

FGL2 as a predictive biomarker for prognosis and immunotherapy in bladder cancer

Background: Metastasis and immunosuppression result in unfavorable prognosis in bladder cancer (BLCA). FGL1 and FGL2 are two members of the fibrinogen-related proteins family, but their potential effects on BLCA remain elusive. Methods: The expression profile of FGL1 and FGL2 in BLCA was analyzed in multiple databases. Furthermore, the expression of FGL2 was validated in BLCA tissues. The predictive capability of FGL2 was evaluated by Kaplan-Meier analysis, univariate analysis, and multivariate Cox regression. A nomogram model was constructed based on FGL2 expression and clinicopathological parameters for clinical practice. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analyses (GSEA) were performed to investigate enrichment in the biological processes. In addition, the correlation between FGL2 and immunological characteristics in the BLCA tumor microenvironment (TME), including tumor-infiltrating immune cells (TICs), cancer-immunity cycles, immune checkpoint molecules (ICPs), immunophenoscores (IPS), and response to anti-PD-L1 immunotherapy was further analyzed. Results: FGL2 was found to be downregulated in BLCA due to hypermethylation of the FGL2 promoter region, which was associated with an unfavorable prognosis. Moreover, BLCA patients with high FGL2 expression exhibited better response to immunotherapy. Conclusions: Our research revealed that FGL2 was downregulated in BLCA and was negatively correlated with DNA methylation. High FGL2 expression was confirmed as an independent risk for prognosis. Moreover, FGL2 is a promising indicator for the response to immunotherapy in patients with BLCA.

FGL2: A new target molecule for coagulation and immune regulation in infectious disease

Infectious diseases are complex inflammatory-immunologic host responses caused by various pathogens, such as viruses, bacteria, parasites, and fungi. In the process of infectious disease development, immune cells are activated, and a substantial number of inflammatory factors are released within the endothelium, which results in coagulation activation and the formation of intravascular thrombi. Furthermore, infection-induced hypercoagulability amplifies the inflammatory response and immune dysregulation. Emerging evidence suggests that fibrinogen-like protein 2 (FGL2) has a crucial role in facilitating procoagulant, pro-inflammatory, and immune-regulatory responses in various infectious diseases. This review illustrates the complex procoagulation and immunoregulatory roles of FGL2, suggesting it could be a target for novel immune interventions in intractable infectious diseases.