Citations

Abstract Alveolar macrophages (AMs) are major lung tissue-resident macrophages capable of proliferating and self-renewal in situ. AMs are vital in pulmonary antimicrobial immunity and surfactant clearance. The mechanisms regulating AM compartment formation and maintenance remain to be fully elucidated currently. In this study, we have explored the roles of mitochondrial transcription factor A (TFAM)–mediated mitochondrial fitness and metabolism in regulating AM formation and function. We found that TFAM deficiency in mice resulted in significantly reduced AM numbers and impaired AM maturation in vivo. TFAM deficiency was not required for the generation of AM precursors nor the differentiation of AM precursors into AMs, but was critical for the maintenance of AM compartment. Mechanistically, TFAM deficiency diminished gene programs associated with AM proliferation and self-renewal and promoted the expression of inflammatory genes in AMs. We further showed that TFAM-mediated AM compartment impairment resulted in defective clearance of cellular debris and surfactant in the lung and increased the host susceptibility to severe influenza virus infection. Finally, we found that influenza virus infection in AMs led to impaired TFAM expression and diminished mitochondrial fitness and metabolism. Thus, our data have established the critical function of TFAM-mediated mitochondrial metabolism in AM maintenance and function.

BATF regulates ILC2-mediated tissue repair and inflammation resolution during acute respiratory virus infection.

Abstract Cytotoxic CD8+ T cells (CTL) are a crucial component of the immune system notable for their ability to eliminate rapidly proliferating malignant cells. However, the T-cell intrinsic factors required for human CTLs to accomplish highly efficient antitumor cytotoxicity are not well defined. By evaluating human CD8+ T cells from responders versus nonresponders to treatment with immune checkpoint inhibitors, we sought to identify key factors associated with effective CTL function. Single-cell RNA-sequencing analysis of peripheral CD8+ T cells from patients treated with anti–PD-1 therapy showed that cells from nonresponders exhibited decreased expression of the cytolytic granule-associated molecule natural killer cell granule protein-7 (NKG7). Functional assays revealed that reduced NKG7 expression altered cytolytic granule number, trafficking, and calcium release, resulting in decreased CD8+ T-cell–mediated killing of tumor cells. Transfection of T cells with NKG7 mRNA was sufficient to improve the tumor-cell killing ability of human T cells isolated from nonresponders and increase their response to anti–PD-1 or anti–PD-L1 therapy in vitro. NKG7 mRNA therapy also improved the antitumor activity of murine tumor antigen–specific CD8+ T cells in an in vivo model of adoptive cell therapy. Finally, we showed that the transcription factor ETS1 played a role in regulating NKG7 expression. Together, our results identify NKG7 as a necessary component for the cytotoxic function of CD8+ T cells and establish NKG7 as a T-cell–intrinsic therapeutic target for enhancing cancer immunotherapy. See related article by Li et al., p. 154.

BACKGROUND Little is known about the autoreactive B cells in antineutrophil cytoplasmic antibody–associated (ANCA-associated) vasculitis (AAV). We aimed to investigate tolerance checkpoints of circulating antigen-specific proteinase 3–reactive (PR3 + ) B cells. METHODS Multicolor flow cytometry in combination with bioinformatics and functional in vitro studies were performed on baseline samples of PBMCs from 154 well-characterized participants of the RAVE trial (NCT00104299) with severely active PR3-AAV and myeloperoxidase-AAV (MPO-AAV) and 27 healthy controls (HCs). Clinical data and outcomes from the trial were correlated with PR3 + B cells (total and subsets). RESULTS The frequency of PR3 + B cells among circulating B cells was higher in participants with PR3-AAV (4.77% median [IQR, 3.98%–6.01%]) than in participants with MPO-AAV (3.16% median [IQR, 2.51%–5.22%]) and participants with AAV compared with HCs (1.67% median [IQR, 1.27%–2.16%], P < 0.001 for all comparisons), implying a defective central tolerance checkpoint in patients with AAV. Only PBMCs from participants with PR3-AAV contained PR3 + B cells capable of secreting PR3-ANCA IgG in vitro, proving they were functionally distinct from those of participants with MPO-AAV and HCs. Unsupervised clustering identified subtle subsets of atypical autoreactive PR3 + memory B cells accumulating through the maturation process in patients with PR3-AAV. PR3 + B cells were enriched in the memory B cell compartment of participants with PR3-AAV and were associated with higher serum CXCL13 levels, suggesting an increased germinal center activity. PR3 + B cells correlated with systemic inflammation (C-reactive protein and erythrocyte sedimentation rate, P < 0.05) and complete remission ( P < 0.001). CONCLUSION This study suggests the presence of defective central antigen-independent and peripheral antigen-dependent checkpoints in patients with PR3-AAV, elucidating the selection process of autoreactive B cells. Trial registration ClinicalTrials.gov NCT00104299. Funding The Vasculitis Foundation, the National Institute of Allergy and Infectious Diseases of the NIH, and the Mayo Foundation for Education and Research.

Respiratory tissue resident–like CD8 + T cells are associated with chronic lung sequelae post-acute COVID-19.

Epithelial-mesenchymal transition (EMT) creates an environment facilitating fibrosis following alveolar epithelial cell injury. IL-23 has important roles in chronic autoimmune conditions like rheumatoid arthritis (RA), but its role in the interstitial lung disease that affects patients with RA is unclear. This study aimed to determine the profibrogenic role of IL-23 on somatic alveolar type I (ATI) epithelial cells. Primary ATI cells were isolated from rats and cultured on plastic dishes for 1–3 wk. After prolonged culture (≥14 days) on rigid culture dishes, primary ATI cells gradually acquired a mesenchymal phenotype, identified by decreased expression of caveolin-1, and reorganization of F-actin cytoskeleton, indicating the initiation of EMT by matrix stiffness. To determine how IL-23 promotes EMT in vitro, transitioning ATI cells, cultured on a stiff substrate for ≥14 days were stimulated with IL-23. The EMT phenotype was significantly enhanced by IL-23, which upregulated α-smooth muscle actin (α-SMA), collagen I/III protein, and decreased caveolin-1. Furthermore, IL-23 significantly promoted cell invasion, as well as apoptotic resistance on transitioning ATI cells. Mechanistically, IL-23-induced EMT was mammalian target of rapamycin/ribosomal protein S6 (mTOR/S6) signaling dependent and reversible by rapamycin. Transcriptional sequencing analysis of human lung fibrosis biopsy tissue revealed key roles for IL-23 in rheumatoid arthritis-associated interstitial lung disease (RA-ILD). This result was further validated by significantly upregulated IL-23 expression at the mRNA level in RA-ILD lung sections. Notably, transitioning ATI epithelial cells were abundantly detected in RA-ILD tissue. Taken together, these data support a role for IL-23 in the pathogenesis of RA lung fibrosis by promoting EMT in alveolar epithelial cells through mTOR/S6 signaling.

Adaptive cellular immunity plays a major role in clearing microbial invasion of mucosal tissues in mammals. Following the clearance of primary pathogens, memory lymphocytes are established both systemically and locally at pathogen entry sites. Recently, resident memory CD8 T and B cells (TRM and BRM respectively), which are parked mainly in non-lymphoid mucosal tissues, were characterized and demonstrated to be essential for protection against secondary microbial invasion. Here we reviewed the current understanding of the cellular and molecular cues regulating CD8 TRM and BRM development, maintenance and function. We focused particularly on elucidating the role of a novel tissue-resident helper T (TRH) cell population in assisting TRM and BRM responses in the respiratory mucosa following viral infection. Finally, we argue that the promotion of TRH responses by future mucosal vaccines would be key to the development of successful universal influenza or coronavirus vaccines, providing long-lasting immunity against a broad spectrum of viral strains.

Background: Although vulnerable plaques are considered the pathological substrate for acute cardiovascular events, the pursuit of imaging surrogate markers for systemic atherothrombotic risk is currently focused on plaque burden. The prognostic value of vulnerable plaque characteristics as novel markers for systemic cardiovascular outcomes remains elusive. Advances in magnetic resonance imaging (MRI) have enabled characterization of the vulnerable carotid plaque. In a prospective study, we tested whether MRI-detected carotid plaque characteristics predict subsequent cardiovascular events. Methods: As part of an event-driven clinical trial, subjects with clinically established atherosclerotic disease were recruited. A multi-sequence protocol was used to measure the volumes of calcification and necrotic core (NC), and to identify the presence of intraplaque hemorrhage (IPH) and thin/ruptured fibrous cap (FC) using published criteria. The primary endpoint included fatal and non-fatal myocardial infarction or ischemic stroke, hospitalization for acute coronary syndrome, and symptom-driven revascularization. Cox regression analysis was used to present results as hazard ratio (HR) with 95% confidence interval (CI). Results: Of 232 subjects recruited, 214 (92.2%) with diagnostic image quality constituted the study population (mean age: 61±9 years; male: 82%; statin use: 94%). Calcification, NC, IPH, and thin/ruptured FC were detected in 48%, 52%, 8% and 14% of subjects, respectively. During a median follow-up of 35.1 months, 18 (8.4%) subjects reached the primary endpoint. MRI-detected plaque characteristics associated with the primary endpoint included larger NC (HR per 1 standard deviation increase in volume [1-SD]: 1.43 [1.16, 1.75], p<0.001), thin/ruptured FC (HR: 4.31 [1.67, 11.12], p=0.003), and marginally IPH (HR: 3.00 [0.99, 9.13], p=0.053). Although calcium deposition is traditionally pursued as a marker for atherosclerosis, subjects with larger calcification (HR per 1-SD: 0.60 [0.26, 1.41], p=0.20) did not show increased risk. Conclusions: Vulnerable plaque characteristics are prevalent in carotid arteries of patients with established atherosclerosis and are predictive of systemic cardiovascular outcomes.

Abstract Aims Associations between growth differentiation factor-15 (GDF-15), cardiovascular outcomes, and exercise capacity among patients with a recent hospitalization for heart failure (HHF) and heart failure with reduced ejection fraction (HFrEF) are unknown. We utilized data from the ‘Functional Impact of GLP-1 for Heart Failure Treatment’ (FIGHT) study to address these knowledge gaps. Methods and results FIGHT was a randomized clinical trial testing the effect of liraglutide (vs. placebo) among 300 participants with HFrEF and a recent HHF. Multivariable regression models evaluated associations between baseline GDF-15 and change in GDF-15 (per 1000 pg/mL increase from baseline to 30 days) with clinical outcomes (at 180 days) and declines in exercise capacity (6 min walk distance ≥ 45 m). At baseline (n = 249), median GDF-15 value was 3221 pg/mL (interquartile range 1938–5511 pg/mL). Participants in the highest tertile of baseline GDF-15 were more likely to be male and have more co-morbidities. After adjustment, an increase in GDF-15 over 30 days was associated with higher risk of death or HHF [hazard ratio 1.35, 95% confidence interval (CI) 1.11–1.64]. In addition, higher baseline GDF-15 (per 1000 pg/mL until 6000 pg/mL) and an increase in GDF-15 over 30 days were associated with declining 6 min walk distance (odds ratio 1.26, 95% CI 1.02–1.55 and odds ratio 1.37, 95% CI 1.12–1.69, respectively). GDF-15 levels remained stable among participants randomized to liraglutide. Conclusions An increase in GDF-15 over 30 days among patients in HFrEF was independently associated with an increased risk of cardiovascular events and declining exercise capacity. These results support the value of longitudinal GDF-15 trajectory in informing risk of heart failure disease progression.

Identification of a CD4 + helper T cell population providing in situ help to B and CD8 + T cells in the respiratory mucosa.