Journal of immunology最新文献

Autophagy serves as a critical regulator of immune responses in sepsis. Macrophages are vital constituents of both innate and adaptive immunity. In this study, we delved into the intricate role of p120-catenin (p120) in orchestrating autophagy in macrophages in response to endotoxin stimulation. Depletion of p120 effectively suppressed LPS-induced autophagy in both J774A.1 macrophages and murine bone marrow-derived macrophages. LPS not only elevated the interaction between p120 and L chain 3 (LC3) I/II but also facilitated the association of p120 with mammalian target of rapamycin (mTOR). p120 depletion in macrophages by small interfering RNA reduced LPS-induced dissociation of mTOR and Unc-51-like kinase 1 (ULK1), leading to an increase in the phosphorylation of ULK1. p120 depletion also enhanced LPS-triggered macrophage apoptosis, as evidenced by increased levels of cleaved caspase 3, 7-aminoactinomycin D staining, and TUNEL assay. Notably, inhibiting autophagy reversed the decrease in apoptosis caused by LPS stimulation in macrophages overexpressing p120. Additionally, the ablation of p120 inhibited autophagy and accentuated apoptosis in alveolar macrophages in LPS-challenged mice. Collectively, our findings strongly suggest that p120 plays a pivotal role in fostering autophagy while concurrently hindering apoptosis in macrophages, achieved through modulation of the mTOR/ULK1 signaling pathway in sepsis. This underscores the potential of targeting macrophage p120 as an innovative therapeutic avenue for treating inflammatory disorders.

CMV infection and Th17 cells are independently associated with increased risk for late allograft loss after renal transplantation. Although CMV-specific Th17 cells are detectable in animal models and nontransplant clinical populations, evidence linking CMV and Th17 cells after renal transplantation remains unclear. This prospective observational study evaluated a cohort of renal transplant recipients during 12 mo posttransplant to assess the presence of CMV-specific Th17 cells in peripheral blood and their relationship to pretransplant CMV serostatus and CMV DNAemia. CMV-specific Th17 cells were identified among CMV serostatus donor (D)+ and/or recipient (R)+ recipients and expanded during both primary (D+/R-) and reactivated (D+/R+, D-/R+) CMV DNAemia. A subset of CMV-specific Th17 cells coexpressed IFN-γ, indicating a Th1/17 phenotype. These Th17 and Th1/17 cells expressed CCR6, CCR5, activation and terminal differentiation markers (CD95, OX40, HLA-DR, CD57), and a central/effector memory phenotype. CMV-specific Th1/17 cells expressed activating/inhibitory receptors (CD57, 4-1BB, CD160, CTLA-4, PD-1) at higher frequencies than Th17 cells. In contrast, staphylococcal enterotoxin B-induced Th17 cells did not expand during CMV DNAemia, did not differ between CMV serostatus groups over time, expressed CCR6, predominantly coexpressed TNF-α, and had lower expression of activating and inhibitory receptors than pp65-specific Th17 and Th1/17 cells. These data show that CMV-specific Th17 cells expand during episodes of CMV DNAemia among renal transplant recipients, and that these virus-specific Th17 and Th1/17 cells have distinct phenotypes from global circulating Th(1)/17 cells. These results suggest a potential proinflammatory pathway by which CMV-induced Th17 cells may contribute to allograft injury, increasing risk for late allograft loss.

Staphylococcus aureus is the major cause of healthcare-associated infections, including life-threatening conditions as bacteremia, endocarditis, and implant-associated infections. Despite adequate antibiotic treatment, the mortality of S. aureus bacteremia remains high. This calls for different strategies to treat this infection. In past years, sequencing of Ab repertoires from individuals previously exposed to a pathogen emerged as a successful method to discover novel therapeutic monoclonal Abs and understand circulating B cell diversity during infection. In this paper, we collected peripheral blood from 17 S. aureus bacteremia patients to study circulating plasmablast responses. Using single-cell transcriptome gene expression combined with sequencing of variable heavy and light Ig genes, we retrieved sequences from >400 plasmablasts revealing a high diversity with >300 unique variable heavy and light sequences. More than 200 variable sequences were synthesized to produce recombinant IgGs that were analyzed for binding to S. aureus whole bacterial cells. This revealed four novel monoclonal Abs that could specifically bind to the surface of S. aureus in the absence of Ig-binding surface SpA. Interestingly, three of four mAbs showed cross-reactivity with Staphylococcus epidermidis. Target identification revealed that the S. aureus-specific mAb BC153 targets wall teichoic acid, whereas cross-reactive mAbs BC019, BC020, and BC021 target lipoteichoic acid. All mAbs could induce Fc-dependent phagocytosis of staphylococci by human neutrophils. Altogether, we characterize the active B cell responses to S. aureus in infected patients and identify four functional mAbs against the S. aureus surface, of which three cross-react with S. epidermidis.

Resident memory T cells (TRM cells) have been described in barrier tissues as having a "sensing and alarm" function where, upon sensing cognate Ag, they alarm the surrounding tissue and orchestrate local recruitment and activation of immune cells. In the immunologically unique and tightly restricted CNS, it remains unclear whether and how brain TRM cells, which express the inhibitory receptor programmed cell death protein 1 (PD-1), alarm the surrounding tissue during Ag re-encounter. Using mouse models, we reveal that TRM cells are sufficient to drive the rapid remodeling of the brain immune landscape through activation of microglia, dendritic cells, NK cells, and B cells, expansion of regulatory T cells, and recruitment of macrophages and monocytic dendritic cells. Moreover, we report that although PD-1 restrained granzyme B upregulation in brain TRM cells reactivated via viral peptide, we observed no apparent effect on cytotoxicity in vivo, or downstream alarm responses within 48 h of TRM reactivation. We conclude that TRM cells are sufficient to trigger rapid immune activation and recruitment in the CNS and may have an unappreciated role in driving neuroinflammation.

Influenza virus is a highly contagious respiratory pathogen causing between 9.4 and 41 million infections per year in the United States in the last decade. Annual vaccination is recommended by the World Health Organization, with the goal to reduce influenza severity and transmission. Ag-specific single B cell sequencing methodologies have opened up new avenues into the dissection of the Ab response to influenza virus. The improvement of these methodologies is pivotal to reduce the associated costs and optimize the operational workflow and throughput, especially in the context of multiple samples. In this study, PBMCs and serum samples were collected longitudinally from eight influenza vaccinees either vaccinated yearly for four consecutive influenza seasons or once for one season. Following the serological and B cell profiling of their polyclonal Ab response to a panel of historical, recent, and next-generation influenza vaccine hemagglutinin (HA) and virus strains, a single multiplexed Ag-specific single B cell sequencing run allowed to capture HA-specific memory B cells that were analyzed for preferential Ig H chain/L chain pairing, isotype/subclass usage, and the presence of public BCR clonotypes across participants. Binding and functional profiles of representative private and public clonotypes confirmed their HA specificity, and their overall binding and functional activity were consistent with those observed at the polyclonal level. Collectively, this high-resolution and multiplexed Ab repertoire analysis demonstrated the validity of this optimized methodology in capturing Ag-specific BCR clonotypes, even in the context of a rare B cell population, such as in the case of the peripheral Ag-specific memory B cells.

Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infection characterized by multiorgan involvement and inflammation. Testing of cellular function ex vivo to understand the aberrant immune response in MIS-C is limited. Despite strong Ab production in MIS-C, SARS-CoV-2 nucleic acid testing can remain positive for 4-6 wk postinfection. Therefore, we hypothesized that dysfunctional cell-mediated Ab responses downstream of Ab production may be responsible for delayed clearance of viral products in MIS-C. In MIS-C, monocytes were hyperfunctional for phagocytosis and cytokine production, whereas NK cells were hypofunctional for both killing and cytokine production. The decreased NK cell cytotoxicity correlated with an NK exhaustion marker signature and systemic IL-6 levels. Potentially providing a therapeutic option, cellular engagers of CD16 and SARS-CoV-2 proteins were found to rescue NK cell function in vitro. Taken together, our results reveal dysregulation in Ab-mediated cellular responses of myeloid and NK cells that likely contribute to the immune pathology of this disease.

CD8+ T cells differentiate into two subpopulations in response to acute viral infection: memory precursor effector cells (MPECs) and short-lived effector cells (SLECs). MPECs and SLECs are epigenetically distinct; however, the epigenetic regulators required for formation of these subpopulations are mostly unknown. In this study, we performed an in vivo CRISPR screen in murine naive CD8+ T cells to identify the epigenetic regulators required for MPEC and SLEC formation, using the acute lymphocytic choriomeningitis virus Armstrong infection model. We identified the ATP-dependent chromatin remodeler CHD7 (chromodomain-helicase DNA-binding protein 7) as a positive regulator of SLEC formation, as knockout (KO) of Chd7 reduced SLECs numerically. In contrast, KO of Chd7 increased the formation of central memory T cells following pathogen clearance yet attenuated memory cell expansion following a rechallenge. These findings establish CHD7 as a novel positive regulator of SLEC and a negative regulator of central memory T cell formation.

Expression of T cell Ig and mucin domain-containing protein 3 (Tim-3) is upregulated on regulatory T cells (Tregs) during chronic viral infections. In several murine and human chronic infections, the expression of Tim-3 is associated with poor control of viral burden and impaired antiviral immune responses. However, the role of Tim-3+ Tregs during persistent viral infections has not been fully defined. We employed an inducible Treg-specific Tim-3 loss-of-function (Tim-3 Treg knockout) murine model to dissect the role of Tim-3 on Tregs during chronic lymphocytic choriomeningitis virus infection. Tim-3 Treg knockout mice exhibited a decrease in morbidity, a more potent virus-specific T cell response, and a significant decrease in viral burden. These mice also had a reduction in the frequency of PD-1+Tim-3+ and PD-1+Tox+ gp33-specific exhausted CD8+ T cells. Our findings demonstrate that modulation of a single surface protein on Tregs can lead to a reduction in viral burden, limit T cell exhaustion, and enhance gp33-specific T cell response. These studies may help to identify Tim-3-directed therapies for the management of persistent infections and cancer.

Type 1 diabetes (T1D) is a chronic autoimmune disease that is caused by a combination of genetic and environmental risk factors. In this study, we sought to determine whether a known genetic risk factor, the rs1990760 single nucleotide polymorphism (SNP) (A946T) in IFIH1, resulted in a gain of function in the MDA5 protein and the effects of this mutation on the regulation of type I IFNs during infection with the diabetogenic virus coxsackievirus B3. We found that in cell lines overexpressing the risk variant IFIH1946T there was an elevated level of basal type I IFN signaling and increased basal IFN-stimulated gene expression. An investigation into the mechanism demonstrated that recombinant MDA5 with the A946T mutation had increased ATPase activity in vitro. We also assessed the effect of this SNP in primary human PBMCs from healthy donors to determine whether this SNP influenced their response to infection with coxsackievirus B3. However, we observed no significant changes in type I IFN expression or downstream induction of IFN-stimulated genes in PBMCs from donors carrying the risk allele IFIH1946T. These findings demonstrate the need for a deeper understanding of how mutations in T1D-associated genes contribute to disease onset in specific cellular contexts.

Expression of IL-15 on the surface of human graft endothelial cells (ECs) bound to the IL-15Rα subunit can increase the activation of CTLs, potentiating allograft rejection. Our previous work showed that surface expression of this protein complex could be induced by alloantibody-mediated complement activation through increased IL-1β synthesis, secretion, and autocrine/paracrine IL-1-mediated activation of NF-κB. In this article, we report that cultured human ECs express eight differently spliced IL-15 transcripts. Remarkably, IL-1β does not alter the expression level of any IL-15 transcript but induces surface expression independently of RNA polymerase II-mediated transcription while requiring new protein translation. Mechanistically, IL-1β causes an NF-κB-mediated reduction in the level of microRNA Let-7c-3p, thereby relieving a block of translation of IL-15 surface protein. Let7c-3p anti-miR can induce EC surface expression of IL-15/IL-15Rα in the absence of complement activation or of IL-1, enabling IL-15 transpresentation to boost CD8 T cell activation. Because of the complexity we have uncovered in IL-15 regulation, we recommend caution in interpreting increased total IL-15 mRNA or protein levels as a surrogate for transpresentation.