Functions and Clinical Relevance of Liver-Derived Immunoglobulins.

Liver is the largest internal organ of the body with vital functions. In addition to its endocrine and exocrine activities, liver also plays a pivotal role in the immune system, including haematopoietic functions. Liver parenchymal cells, which are epithelial cells, have been found to possess innate immune functions by expressing pattern-recognition receptors (PRRs), producing complement components, and secreting cytokines. Intriguingly, in recent years, it has been discovered that liver epithelial cells also produce immunoglobulins (Igs), which have long been thought to be produced exclusively by B cells. Notably, even liver epithelial cells from B lymphocyte-deficient mice, including SCID mice and µMT mice, could also produce Igs. Compelling evidence has revealed both the physiological and pathological functions of liver-derived Igs. For instance, liver epithelial cells-derived IgM can serve as a source of natural and specific antibodies that contribute to innate immune responses, while liver-produced IgG can act as a growth factor to promote cell proliferation and survival in normal hepatocytes and hepatocarcinoma. Similar to that in B cells, the toll-like receptor 9 (TLR9)-MyD88 signaling pathway is also actively involved in promoting liver epithelial cells to secrete IgM. Liver-derived Igs could potentially serve as biomarkers, prognostic indicators, and therapeutic targets in the clinical setting, particularly for liver cancers and liver injury. Nevertheless, despite significant advances, much remains unknown about the mechanisms governing Ig transcription in liver cells, as well as the detailed functions of liver-derived Igs and their involvement in diseases and adaptive immunity. Further studies are still needed to reveal these underlying, undefined issues related to the role of liver-derived Igs in both immunity and diseases.

Molluscan pleiotropic FADD involved in innate immune signaling and induces apoptosis.

Fas-associated protein with death domain (FADD) was initially identified as a crucial adaptor protein in the apoptotic pathway mediated by death receptor (DR). Subsequently, many studies have confirmed that FADD plays a vital role in innate immunity and inflammatory responses in animals. However, the function of this pleiotropic molecule in mollusk species has not been well explored. In this study, we successfully verified the gene sequence of FADD in the Zhikong scallop (Chlamys farreri) and designated it as CfFADD. The CfFADD protein contains a conserved death effector and death domains. Phylogenetic analysis showed that CfFADD is a novel addition to the molluscan FADD family with a close evolutionary relationship with molluscan FADD subfamily proteins. CfFADD mRNA expression in various scallop tissues was significantly induced by challenge with pathogen-associated molecular patterns (lipopolysaccharide, peptidoglycan, and poly(I:C)), suggesting its role in innate immunity in scallops. Co-immunoprecipitation showed that CfFADD interacted with the scallop DR (tumor necrosis factor receptor) and a signaling molecule involved in the Toll-like receptor pathway (interleukin-1 receptor-associated kinase), confirming that CfFADD may be involved in DR-mediated apoptosis and innate immune signaling pathways. Further studies showed that CfFADD interacted with CfCaspase-8 and activated caspase-3. HEK293T cells exhibited distinct apoptotic features after transfection with a CfFADD-expression plasmid, suggesting a functional DR-FADD-caspase apoptotic pathway in scallops. Overexpression of CfFADD led to a significant dose-dependent activation of interferon ß and nuclear factor-κB reporter genes, demonstrating the key role of CfFADD in innate immunity. In summary, our research has confirmed the critical roles of CfFADD in innate immunity and apoptosis and provides valuable information for developing comparative immunology theories.

TRIM26 facilitates PRV infection through NDP52-mediated autophagic degradation of MAVS.

Pseudorabies virus (PRV) has evolved multiple strategies to evade host antiviral responses to benefit virus replication and establish persistent infection. Recently, tripartite motif 26 (TRIM26), a TRIM family protein, has been shown to be involved in a broad range of biological processes involved in innate immunity, especially in regulating viral infection. Herein, we found that the expression of TRIM26 was significantly induced after PRV infection. Surprisingly, the overexpression of TRIM26 promoted PRV production, while the depletion of this protein inhibited virus replication, suggesting that TRIM26 could positively regulate PRV infection. Further analysis revealed that TRIM26 negatively regulates the innate immune response by targeting the RIG-I-triggered type I interferon signalling pathway. TRIM26 was physically associated with MAVS independent of viral infection and reduced MAVS expression. Mechanistically, we found that NDP52 interacted with both TRIM26 and MAVS and that TRIM26-induced MAVS degradation was almost entirely blocked in NDP52-knockdown cells, demonstrating that TRIM26 degrades MAVS through NDP52-mediated selective autophagy. Our results reveal a novel mechanism by which PRV escapes host antiviral innate immunity and provide insights into the crosstalk among virus infection, autophagy, and the innate immune response.

Weep and sweep and the broom: tuft cell acetylcholine limits the worm.

Two studies defined how tuft cell acetylcholine promotes parasite expulsion. Billip et al. demonstrated that acetylcholine increases water secretion, to promote the 'weep' response. Ndjim et al. found that tuft cell acetylcholine has a direct effect on worm fecundity. Both processes are only effective in the remodeled epithelium when the rare tuft cells have become abundant.

Suppression of MyD88 disturbs gut microbiota and activates the NLR pathway and hence fails to ameliorate DSS-induced colitis.

Background: Myeloid differentiation factor 88 (MyD88) is the core adaptor for Toll-like receptors defending against microbial invasion and initiating a downstream immune response during microbiota-host interaction. However, the role of MyD88 in the pathogenesis of inflammatory bowel disease is controversial. This study aims to investigate the impact of MyD88 on intestinal inflammation and the underlying mechanism. Methods: MyD88 knockout (MyD88-/-) mice and the MyD88 inhibitor (TJ-M2010-5) were used to investigate the impact of MyD88 on acute dextran sodium sulfate (DSS)-induced colitis. Disease activity index, colon length, histological score, and inflammatory cytokines were examined to evaluate the severity of colitis. RNA transcriptome analysis and 16S rDNA sequencing were used to detect the potential mechanism. Results: In an acute DSS-colitis model, the severity of colitis was not alleviated in MyD88-/- mice and TJ-M2010-5-treated mice, despite significantly lower levels of NF-κB activation being exhibited compared to control mice. Meanwhile, 16S rDNA sequencing and RNA transcriptome analysis revealed a higher abundance of intestinal Proteobacteria and an up-regulation of the nucleotide oligomerization domain-like receptors (NLRs) signaling pathway in colitis mice following MyD88 suppression. Further blockade of the NLRs signaling pathway or elimination of gut microbiota with broad-spectrum antibiotics in DSS-induced colitis mice treated with TJ-M2010-5 ameliorated the disease severity, which was not improved solely by MyD88 inhibition. After treatment with broad-spectrum antibiotics, downregulation of the NLR signaling pathway was observed. Conclusion: Our study suggests that the suppression of MyD88 might be associated with unfavorable changes in the composition of gut microbiota, leading to NLR-mediated immune activation and intestinal inflammation.

Photodynamic Therapy Synergizes CD47 Blockade Strategy for Enhanced Antitumor Therapy.

The antitumor strategies based on innate immunity activation have become favored by researchers in recent years. In particular, strategies targeting antiphagocytic signaling blockade to enhance phagocytosis have been widely reported. For example, the addition of prophagocytic signals such as calreticulin could make the strategy significantly more effective. In this study, an antitumor strategy that combines photodynamic therapy (PDT) with CD47 blockade has been reported. This approach promotes the maturation of dendritic cells and the presentation of tumor antigens by PDT-mediated tumor immunogenic cell death, as well as the enhancement of cytotoxic T lymphocyte infiltration in tumor areas and the phagocytic activity of phagocytes. Furthermore, the downregulation and blockage of CD47 protein could further promote phagocytic activity, strengthen the innate immune system, and ultimately elevate the antitumor efficacy and inhibit tumor metastasis.

Unconventional posttranslational modification in innate immunity.

Pattern recognition receptors (PRRs) play a crucial role in innate immunity, and a complex network tightly controls their signaling cascades to maintain immune homeostasis. Within the modification network, posttranslational modifications (PTMs) are at the core of signaling cascades. Conventional PTMs, which include phosphorylation and ubiquitination, have been extensively studied. The regulatory role of unconventional PTMs, involving unanchored ubiquitination, ISGylation, SUMOylation, NEDDylation, methylation, acetylation, palmitoylation, glycosylation, and myristylation, in the modulation of innate immune signaling pathways has been increasingly investigated. This comprehensive review delves into the emerging field of unconventional PTMs and highlights their pivotal role in innate immunity.

Autoimmunity in patients with inborn errors of immunity: A case series.

OBJECTIVE: To assess the prevalence of systemic and organ-specific autoimmunity among individuals with human inborn errors of immunity (IEI). METHODS: Retrospective study. We recorded demographic variables, type of immunodeficiency, and systemic and organ specific autoimmunity. RESULTS: We included 48 patients (54.1% men) with mean age of 32.1 years. The most common IEIs included combined immunodeficiency with syndromic features (31.2%) and predominantly antibody deficiency (20.1%). We observed autoimmunity in 15 patients (31.2%): 12 organ-specific autoimmunity and 5 systemic autoimmunity, not mutually exclusive groups. Organ-specific autoimmunity preceded the onset of IEI in 5 patients, was concurrent in one patient, and developed after the diagnosis of IEI in 6 cases. From the systemic autoimmunity group, we observed polyarteritis nodosa (n = 2), antiphospholipid syndrome (APS) (n = 2), and overlap of limited systemic sclerosis/APS/Sjögren's syndrome (n = 1), and in all cases, this occurred after the IEI diagnosis. CONCLUSION: Our findings confirm the coexistence of autoimmunity and IEI. This overlap may be attributed to B and T cell disorders, as well as potential alterations in the microbiota in these patients.

Mutual regulations between Toxoplasma gondii and type I interferon.

In the decades since the discovery, Type I interferon (IFN-I) has been intensively studied for their antiviral activity. However, increasing evidences suggest that it may also play an important role in the infection of Toxoplasma gondii, a model organism for intracellular parasites. Recent studies demonstrated that the induction of IFN-I by the parasite depends on cell type, strain genotype, and mouse strain. IFN-I can inhibit the proliferation of T. gondii, but few studies showed that it is beneficial to the growth of the parasite. Meanwhile, T. gondii also can secrete proteins that impact the pathway of IFN-I production and downstream induced interferon-stimulated genes (ISGs) regulation, thereby escaping immune destruction by the host. This article reviews the major findings and progress in the production, function, and regulation of IFN-I during T. gondii infection, to thoroughly understand the innate immune mechanism of T. gondii infection, which provides a new target for subsequent intervention and treatment.

Study of gene polymorphisms in Toll-like receptor 2 in patients with acute lymphoblastic leukemia.

Objectives: Acute Lymphoblastic Leukemia (ALL) is a multifactorial disease that results from the interaction between multiple genetic factors. ALL is characterized by uncontrolled production of hematopoietic precursor cells of the lymphoid progenitors within the bone marrow. The development of hematological malignancies has been associated with malignant-like cells that express low levels of immunogenic surface molecules, thus, facilitating their escape from cellular antineoplastic immune responses. This risk may be partly influenced by variations in polymorphic genes that control immune function and regulation. Toll-like receptors (TLRs) are well known pattern recognition receptors playing key role in innate immune response. Abnormal expression and dysregulation of TLRs will provide an opportunity for cancer cells to escape from the immune system and enhance their proliferation and angiogenesis. Toll-like receptor 2 (TLR2) play an essential role in innate immunity. Single nucleotide polymorphisms (SNPs) are present in a number of TLR genes and have been associated with various disorders. Methods: In this study, 265 subjects have been divided into two groups included 150 patients with ALL and115 healthy volunteers. All subjects were genotyped using TaqMan PCR techniques. In total, Five SNPs were statistically evaluated in the TLR2 (rs1898830 A/G, rs3804099 T/C, rs3804100 T/C, rs1339 T/C, and rs1337 C/G), which may influence the susceptibility of ALL. Minor allele frequency and genotype distribution were compared across the study groups, and the relative risk and differences between patients and controls were estimated. Moreover, the mRNA expression level was evaluated in patients with ALL and the matched healthy individuals by Real-Time Quantitative Reverse Transcription PCR (qRT-PCR). Results: TLR2 rs1898830 A/G; rs3804099 T/C; rs3804100 T/C; rs1339 T/C, were significantly decrease the risk in our population, overall and for certain subtypes and ALL samples exhibited significant increase in the mRNA levels of TLR2. Conclusions: This study shows that TLR2 could be an independent prognostic factor of ALL risks in the Saudi population. Suggesting that genetic variation in genes associated with an immune response may be important in the etiology of ALL. In addition, the results herein revealed that TLR2 overexpression is associated with ALL and has diverse biological significance in the context of the complex relationship between inflammation and cancer development. Therefore, these data could open further studies to explore the possible clinical relevance of TLRs as pathological markers for Leukemia and enhance the strategies regarding hematological malignancies prevention based on their gene expression.

Multiple Chitin- or Avirulent Strain-Triggered Immunity Induces Microbiome Reassembly in Rice.

Magnaporthe oryzae is one of the most important fungal pathogens of rice. Chitin and avirulent strains can induce two layers of immunity response, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI), in rice with cognate R genes. However, little is known about the assembly of the rice microbiome induced by PTI and ETI in rice. In this study, we investigate the impact of continuous treatment of the avirulent M. oryzae strain with AvrPi9 and chitin on the bacterial endophytic community of rice varieties harboring resistant gene Pi9 and their antagonistic activity against rice blast fungus. Analysis of the 16S rRNA showed a significant increase in the diversity and microbial co-occurrence network complexity and the number of beneficial taxa-Bacillus, Pseudomonas, Microbacterium, and Stenotrophomonas spp.-following the chitin and avirulent strain treatments. The antifungal assay with bacterial endophytes recovered from the leaves showed few bacteria with antagonistic potential in rice treated with avirulent strains, suggesting that the sequential treatment of the avirulent strain decreased the antagonistic bacteria against M. oryzae. Moreover, we identified Bacillus safensis Ch_66 and Bacillus altitudinis Nc_68 with overall antagonistic activities in vivo and in vitro. Our findings provide a novel insight into rice microbiome assembly in response to different innate immunity reactions.

Humoral and Innate Immunological Profile of Paediatric Recipients of Pfizer-BioNTech BNT162b2 mRNA Vaccine.

The Pfizer-BioNTech vaccine was one of the essential tools in curtailing the COVID-19 pandemic. Unlike conventional vaccines, this newly approved mRNA vaccine is taken up by cells, which leads to the synthesis of the specific viral Spike antigen. The vaccine was initially introduced for adults, and the immunological profile of adult recipients is well-characterized. The vaccine was approved for paediatric use much later after its efficacy and safety had been confirmed in children. However, the complete picture of how the paediatric immune system in children reacts to the vaccine is not well documented. Therefore, in order to better understand the immune response in children, we analysed the humoral response, immune cell count, and interferon signalling in paediatric vaccine recipients ranging between 5 and 17 years of age. Our findings suggest that the paediatric recipients elicit a robust humoral response that is sustained for at least three months. We also found that the vaccine triggered a transient lymphocytopenia similar to that observed during viral infection. Interestingly, we also found that the vaccine may sensitise the interferon signalling pathway, priming the cells to mount a potent response when exposed to interferons during a subsequent infection. The study offers new insights into the workings of the paediatric immune system and innate immunity, thereby opening the doors for further research in this field.

STING trafficking activates MAPK-CREB signaling to trigger regulatory T cell differentiation.

The Type-I interferon (IFN-I) response is the major outcome of stimulator of interferon genes (STING) activation in innate cells. STING is more abundantly expressed in adaptive T cells; nevertheless, its intrinsic function in T cells remains unclear. Intriguingly, we previously demonstrated that STING activation in T cells activates widespread IFN-independent activities, which stands in contrast to the well-known STING-mediated IFN response. Here, we have identified that STING activation induces regulatory T cells (Tregs) differentiation independently of IRF3 and IFN. Specifically, the translocation of STING from the endoplasmic reticulum to the Golgi activates mitogen-activated protein kinase (MAPK) activity, which subsequently triggers transcription factor cAMP response element-binding protein (CREB) activation. The activation of the STING-MAPK-CREB signaling pathway induces the expression of many cytokine genes, including interleukin-2 (IL-2) and transforming growth factor-beta 2 (TGF-ß2), to promote the Treg differentiation. Genetic knockdown of MAPK p38 or pharmacological inhibition of MAPK p38 or CREB markedly inhibits STING-mediated Treg differentiation. Administration of the STING agonist also promotes Treg differentiation in mice. In the Trex1-/- autoimmune disease mouse model, we demonstrate that intrinsic STING activation in CD4+ T cells can drive Treg differentiation, potentially counterbalancing the autoimmunity associated with Trex1 deficiency. Thus, STING-MAPK-CREB represents an IFN-independent signaling axis of STING that may have profound effects on T cell effector function and adaptive immunity.

Icariside I enhances the effects of immunotherapy in gastrointestinal cancer via targeting TRPV4 and upregulating the cGAS-STING-IFN-I pathway.

Gastrointestinal cancer is among the most common cancers worldwide. Immune checkpoint inhibitor-based cancer immunotherapy has become an innovative approach in cancer treatment; however, its efficacy in gastrointestinal cancer is limited by the absence of infiltration of immune cells within the tumor microenvironment. Therefore, it is therefore urgent to develop a novel therapeutic drug to enhance immunotherapy. In this study, we describe a previously unreported potentiating effect of Icariside I (ICA I, GH01), the main bioactive compound isolated from the Epimedium species, on anti-tumor immune responses. Mechanistically, molecular docking and SPR assay result show that ICA I binding with TRPV4. ICA I induced intracellular Ca2+ increasing and mitochondrial DNA release by targeting TRPV4, which triggered cytosolic ox-mitoDNA release. Importantly, these intracellular ox-mitoDNA fragments were taken up by immune cells in the tumor microenvironment, which amplified the immune response. Moreover, our study shows the remarkable efficacy of sequential administration of ICA I and anti-α-PD-1 mAb in advanced tumors and provides a strong scientific rationale for recommending such a combination therapy for clinical trials. ICA I enhanced the anti-tumor effects with PD-1 inhibitors by regulating the TRPV4/Ca2+/Ox-mitoDNA/cGAS/STING axis. We expect that these findings will be translated into clinical therapies, which will benefit more patients with cancer in the near future.

Human pulmonary microvascular endothelial cells respond to DAMPs from injured renal tubular cells.

Acute kidney injury (AKI) causes distant organ dysfunction through yet unknown mechanisms, leading to multiorgan failure and death. The lungs are one of the most common extrarenal organs affected by AKI, and combined lung and kidney injury has a mortality as high as 60%-80%. One mechanism that has been implicated in lung injury after AKI involves molecules released from injured kidney cells (DAMPs, or damage-associated molecular patterns) that promote a noninfectious inflammatory response by binding to pattern recognition receptors (PRRs) constitutively expressed on the pulmonary endothelium. To date there are limited data investigating the role of PRRs and DAMPs in the pulmonary endothelial response to AKI. Understanding these mechanisms holds great promise for therapeutics aimed at ameliorating the devastating effects of AKI. In this study, we stimulate primary human microvascular endothelial cells with DAMPs derived from injured primary renal tubular epithelial cells (RTECs) as an ex-vivo model of lung injury following AKI. We show that DAMPs derived from injured RTECs cause activation of Toll-Like Receptor and NOD-Like Receptor signaling pathways as well as increase human primary pulmonary microvascular endothelial cell (HMVEC) cytokine production, cell signaling activation, and permeability. We further show that cytokine production in HMVECs in response to DAMPs derived from RTECs is reduced by the inhibition of NOD1 and NOD2, which may have implications for future therapeutics. This paper adds to our understanding of PRR expression and function in pulmonary HMVECs and provides a foundation for future work aimed at developing therapeutic strategies to prevent lung injury following AKI.

Exploring TRIM proteins' role in antiviral defense against influenza A virus and respiratory coronaviruses.

Numerous tripartite motif (TRIM) proteins, identified as E3 ubiquitin ligases, participate in various viral infections through ubiquitylation, ISGylation, and SUMOylation processes. Respiratory viruses, particularly influenza A virus (IAV) and respiratory coronaviruses (CoVs), have severely threatened public health with high morbidity and mortality, causing incalculable losses. Research on the regulation of TRIM proteins in respiratory virus infections is crucial for disease prevention and control. This review introduces TRIM proteins, summarizes recent discoveries regarding their roles and molecular mechanisms in IAV and CoVs infections, discusses current research gaps, and explores potential future trends in this rapidly developing field. It aims to enhance understanding of virus-host interactions and inform the development of new molecularly targeted therapies.

Molecular Mechanisms and Potential Antiviral Strategies of Liquid-Liquid Phase Separation during Coronavirus Infection.

Highly pathogenic coronaviruses have caused significant outbreaks in humans and animals, posing a serious threat to public health. The rapid global spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has resulted in millions of infections and deaths. However, the mechanisms through which coronaviruses evade a host's antiviral immune system are not well understood. Liquid-liquid phase separation (LLPS) is a recently discovered mechanism that can selectively isolate cellular components to regulate biological processes, including host antiviral innate immune signal transduction pathways. This review focuses on the mechanism of coronavirus-induced LLPS and strategies for utilizing LLPS to evade the host antiviral innate immune response, along with potential antiviral therapeutic drugs and methods. It aims to provide a more comprehensive understanding and novel insights for researchers studying LLPS induced by pandemic viruses.

Knockdown of DJ-1 Resulted in a Coordinated Activation of the Innate Immune Antiviral Response in HEK293 Cell Line.

PARK7, also known as DJ-1, plays a critical role in protecting cells by functioning as a sensitive oxidation sensor and modulator of antioxidants. DJ-1 acts to maintain mitochondrial function and regulate transcription in response to different stressors. In this study, we showed that cell lines vary based on their antioxidation potential under basal conditions. The transcriptome of HEK293 cells was tested following knockdown (KD) of DJ-1 using siRNAs, which reduced the DJ-1 transcripts to only 12% of the original level. We compared the expression levels of 14k protein-coding transcripts and 4.2k non-coding RNAs relative to cells treated with non-specific siRNAs. Among the coding genes, approximately 200 upregulated differentially expressed genes (DEGs) signified a coordinated antiviral innate immune response. Most genes were associated with the regulation of type 1 interferons (IFN) and the induction of inflammatory cytokines. About a quarter of these genes were also induced in cells treated with non-specific siRNAs that were used as a negative control. Beyond the antiviral-like response, 114 genes were specific to the KD of DJ-1 with enrichment in RNA metabolism and mitochondrial functions. A smaller set of downregulated genes (58 genes) was associated with dysregulation in membrane structure, cell viability, and mitophagy. We propose that the KD DJ-1 perturbation diminishes the protective potency against oxidative stress. Thus, it renders the cells labile and responsive to the dsRNA signal by activating a large number of genes, many of which drive apoptosis, cell death, and inflammatory signatures. The KD of DJ-1 highlights its potency in regulating genes associated with antiviral responses, RNA metabolism, and mitochondrial functions, apparently through alteration in STAT activity and downstream signaling. Given that DJ-1 also acts as an oncogene in metastatic cancers, targeting DJ-1 could be a promising therapeutic strategy where manipulation of the DJ-1 level may reduce cancer cell viability and enhance the efficacy of cancer treatments.