Discovery immunology最新文献

Introduction: CASPASE8 promotes both cell death and survival by acting as a trigger of apoptosis and a repressor of necroptosis. In T cells, the function and mechanisms of CASPASE8 are incompletely understood.

Methods: Here, we analysed mice in which Casp8 was conditionally deleted in T cells at different stages of development.

Results: In mice with deletion early in T cell development, we observed a modest reduction in early thymic progenitors and a striking absence of NKT cells in the thymus. Amongst mature peripheral T cells, there was a substantial and specific reduction in the CD8 T cell compartment, which included naive, central memory and virtual memory subsets. Using a tamoxifen-inducible CD8^CreERT to delete Casp8 revealed an acute requirement for continued CASPASE8 expression for survival of a fraction of mature CD8 T cells. Analysing Casp8-deficient mice that express a kinase dead RIPK1 suggested that in vivo, necroptosis contributed to death of thymic progenitors and CD8EM and CD8CM subsets. However, kinase dead RIPK1 failed to restore NKT cell development or rescue the loss of CD4EM and CD4CM in mixed bone marrow chimeras, and only partially rescued CD8 VM T cell.

Conclusions: Together, these observations suggest that CASPASE8 promotes T cell survival independent of its established role in repressing RIPK1-dependent necroptosis.

Introduction: Natural killer (NK) cells are central to innate immune responses but they also influence adaptive immunity. Evidence suggests that NK cells are involved in protective immune responses induced by the Bacille Calmette Guerin (BCG) vaccine. In cattle, vaccination with BCG provides significant protection against infection with Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). Bovine NK cells were previously shown to traffic from BCG vaccination sites in afferent lymph, and to be activated reciprocally through interactions with dendritic cells (DC) to drive high-level interferon gamma secretion. To further define roles for bovine NK cells in the induction of BCG vaccine-mediated immunity, we examined alterations in their frequency, location, and aggregation in lymph nodes (LN) draining immunization sites.

Materials and methods: Calves were either not vaccinated, vaccinated with BCG once, or were re-vaccinated. The frequency and localization of NK cells in draining LN was examined by immunohistochemistry and immunofluorescence, and statistical analyses of imaging outputs were performed.

Results: While increased numbers of NK cells were found in BCG-draining LN, there were no significant alterations in location, nor the clustering or aggregation of NK cells. Re-vaccination with BCG had little impact on NK cell numbers or location.

Conclusion: BCG vaccination induced changes in NK cell frequency in bovine LN. Further studies of NK cell function and co-localization with subsets of DC and T cells will be important to define the roles of these cells in the induction of protective immunity in bTB.

Introduction: The fluoroquinolone levofloxacin is often selected for use prophylactically as well as during respiratory infections. However, studies on how these antibiotics may alter innate immunity, as opposed to their bactericidal activity, are limited.

Materials & methods: We employed a murine model of therapeutically relevant antibiotic dosing to investigate the effect of prophylactic levofloxacin treatment on innate immunity.

Results: We observed mild pathology at the barrier sites of both the lung and colon in terms of alveolar space and goblet cell numbers, respectively. Although we saw no alteration in lung immune populations of neutrophils, eosinophils, or dendritic cells, we did see heightened expression of macrophage inducible nitric oxide synthase (iNOS). Interestingly this was only present in the shorter-lived CD206- interstitial macrophage subset and not observed in the long-lived resident alveolar population. Within the large intestine levofloxacin also targeted iNOS expression in the shorter-lived TIM4-CD4+ population but conversely inhibiting expression in the microbially rich colon. We therefore utilized the bone marrow-derived macrophage system, devoid of microbial interactions and demonstrated that levofloxacin had a direct effect on driving iNOS expression and increasing phagocytosis but only when present in developing macrophages and not mature macrophage populations. Our macrophage observations were replicated in ciprofloxacin, but not doxycycline-treated animals, indicating a fluoroquinolone specific action. Mechanistically, fluoroquinolone treatment was associated with mitochondrial hyperpolarization, indicating a direct alteration of macrophage immunity via off target effects.

Conclusion: Collectively, this study demonstrates a direct action of fluoroquinolones on macrophage immunity, which should be considered when selecting antibiotics for tissue specific and prophylactic use.

Effective immune defence and pathogen clearance requires coordination between innate and adaptive immune responses. However, virulent African swine fever virus (ASFV), which has a high case fatality rate in pigs, causes severe disease by exploiting multiple immune evasion strategies to suppress host responses. The global spread of Georgia 2007/1 and its derivatives poses a significant threat to the pig industry and global food security. Although modified live virus vaccines for ASF exist, multiple safety concerns have restricted their use internationally. Conversely, subunit vaccine candidates have not matched the protective efficacy of modified live virus vaccines. This highlights the need to further investigate ASFV-induced immunopathology to support the development of next-generation ASF vaccines. Immune dynamics in whole blood and lymphoid tissues were examined over time after oronasal infection with Georgia 2007/1. CD4⁺ T cells, γδ-TCR⁺ T cells and CD21⁺ B cells were impacted by lymphopenia, and initial immune activation was detected. However, as the disease progressed, impaired maintenance and depletion of adaptive immune cells, such as CD4⁺ T cells and professional antigen-presenting dendritic cells and macrophages, important mediators at the innate-adaptive immune interface, was observed. This reduction of cells may have compromised the innate-adaptive immune axis, weakening host ability to mount a robust adaptive immune response and potentially contributing to disease progression. Differential ASFV infection profiles within the spleen were also detected, highlighting the diversity of ASFV cellular tropism. Further investigation into the innate-adaptive immune axis is needed to better understand its role in ASFV infection.

Introduction: Neutrophils are innate immune cells that play a central role in the inflammatory response. They produce an array of destructive molecules and anti-microbial proteases that characterize the cells as front-line defenders, crucial to host defence. It is now appreciated that neutrophils produce and respond to a variety of inflammatory signals and are able to regulate both the innate and adaptive immune responses. However, the mechanisms by which neutrophils respond to different inflammatory signals to regulate their own function and the functions of other immune cells are incompletely defined.

Methods: In this study, we performed RNA sequencing of healthy human neutrophils exposed for 1 h to a range of pro-inflammatory cytokines.

Results: Granulocyte/macrophage colony-stimulating factor and tumour necrosis factor alpha induced significant changes in 1651 and 693 genes, respectively (adj. P < 0.05) including activation of genes regulating apoptosis and encoding cytokines and chemokines that can drive the differentiation and activation of CD4 T-cells. Stimulation of neutrophils with granulocyte colony-stimulating factor, interferon alpha, interferon gamma, interleukin-1 beta, or interleukin-8 resulted in expression of discrete gene sets and differential activation of signalling pathways including changes in cell adhesion and migration, immune receptor expression, apoptosis, and production of pro-inflammatory prostaglandins.

Conclusion: This work defines the differential gene expression patterns in neutrophils exposed to different regulatory cytokines. This is important in both increasing our understanding of the role of neutrophils in driving innate and adaptive immune responses and, importantly, for deconvoluting the neutrophil gene expression signatures observed in inflammatory diseases.

Introduction: Factors regulating the severity of pneumonitis during viral infections remain unresolved. We previously found higher expression of protein S (PROS1) in lung epithelium of mild compared to severe coronavirus disease 2019 (COVID-19) patients. We hypothesized that PROS1 may protect the upper airways by regulating epithelial and myeloid cell responses during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Methods: To test this, in vitro air-liquid interface (ALI) cultures of primary healthy human lung epithelial cells were infected with SARS-CoV-2. This model, validated through immunofluorescent staining, confocal microscopy, and single-cell RNA-sequencing, replicated pathogenic changes seen in the lungs of COVID-19. Regulation and secretion of PROS1, along with multiple soluble mediators, were quantified in control and infected cultures using ELISAs.

Results: We found that PROS1 is present in the basal cells of healthy pseudostratified epithelium and is released during SARS-CoV-2 infection through an IFN-mediated process. Transcriptome analysis revealed that PROS1 downregulated the SARS-CoV-2-induced proinflammatory phenotypes of basal cells, transforming pathogenic CXCL10/11^high into a regenerative S100A2^posKRT^high basal cell phenotype. In parallel, SARS-CoV-2 increased the secretion of M-CSF from epithelial cells, which induced the expression of PROS1 receptor MERTK on monocytes interacting with the lung epithelium. PROS1, in turn, shifted SARS-CoV-2-induced pathogenic monocyte phenotypes toward a phenotype with increased MHC class II.

Conclusion: These findings highlight the crucial role of PROS1 in protecting against severe lung pathology caused by SARS-CoV-2, by reducing epithelial- and monocyte-derived inflammation, promoting pro-repair epithelial phenotypes, and enhancing antigen presentation in myeloid cells.

Introduction: The Tasmanian devil is threatened by two deadly transmissible Schwann cell cancers. A vaccine to protect Tasmanian devils from both devil facial tumour 1 (DFT1) and devil facial tumour 2 (DFT2), and improved understanding of the cancer cell biology, could support improved conservation actions.

Methods: Previous transcriptomic analysis has implicated phenotypic cellular plasticity as a potential immune escape and survival mechanism of DFT1 cells. This phenotypic plasticity facilitates transition from a myelinating Schwann cell to a repair Schwann cell phenotype that exhibits mesenchymal characteristics. Here, we have identified cytokines and growth factors differentially expressed across DFT cell phenotypes and investigated their role in driving phenotypic plasticity and oncogenic properties of DFT cells.

Results: Our results show that NRG1, IL16, TGFβ1, TGFβ2, and PDGFAA/AB proteins have significant and distinct effects on the proliferation rate, migratory capacity and/or morphology of DFT cells. Specifically, PDGFR signalling, induced by PDGFAA/AB, was a strong enhancer of cell proliferation and migration, while TGFβ1 and TGFβ2 induced epithelial-mesenchymal transition (EMT)-like changes, inhibited proliferation and increased migratory capacity.

Conclusion: These findings suggest complex interactions between cytokine signalling, phenotypic plasticity, growth and survival of DFTs. Signalling pathways implicated in the propagation of DFT are potential targets for therapeutic intervention and vaccine development for Tasmanian devil conservation.

[This corrects the article DOI: 10.1093/discim/kyae018.].

Introduction: Cell metabolism plays an important role in immune effector responses and through responding to metabolic signals, immune cells can adapt and regulate their function. Arginine metabolism in dendritic cells (DC) has been shown to reduce T cell activation; however, it is unclear how this immunosuppressive state is induced.

Method: To address this issue, we examined the immunomodulatory capacity of various metabolites from arginine metabolism.

Results: Through the use of a recently described DC:T cell interaction assay and flow cytometry we demonstrated that spermidine most significantly inhibited DC activation, preventing subsequent interactions with CD4 T cells. DC function could be restored by addition of inhibitors of spermidine metabolism via the eIF5A-hypusine axis, required for expression of some mitochondrial enzymes. We also demonstrated that the spermidine induced-immunosuppressive state protected DC against activation-induced loss of mitochondrial capacity for energy generation, which was also hypusination dependent.

Conclusion: Taken together, these data demonstrate that spermidine is the key immunomodulatory component downstream of arginine metabolism and that it mediates this effect by stimulating hypusination-dependent protection of OXPHOS in DC, which in turn results in a reduced ability of DC to activate and interact with T cells. This pathway may be utilized by the immune system to regulate excessive immune responses but could also be exploited by pathogens as a method of immune evasion.