Eosinophilic chronic rhinosinusitis (ECRS) is a subtype of chronic rhinosinusitis (CRS) that is characterized by intractable nasal polyp formation. Eosinophil-derived neurotoxin (EDN) is an eosinophil granule protein that is closely related to allergic inflammation, but the pathological implications of EDN in ECRS remain unknown. In this study, we evaluated the function of EDN in ECRS pathogenesis and assessed its potential as a disease activity marker. Serum EDN levels were significantly higher in patients with ECRS than in those with other nasal and paranasal diseases, and were positively correlated with clinical disease activity. Production of EDN from isolated human eosinophils was induced by stimulation with IL-5 in vitro. Human nasal epithelial cells were stimulated with EDN, and the resultant changes in gene expression were detected by RNA sequencing. Pathway analysis revealed that the major canonical pathway affected by EDN stimulation was ‘regulation of the epithelial–mesenchymal transition pathway’; the only gene in this pathway to be up-regulated was matrix metalloproteinase 9 (MMP-9). Consistent with this, immunostaining analysis revealed intense staining of both EDN and MMP-9 in nasal polyps from patients with ECRS. In conclusion, our data demonstrate that serum EDN level is a useful marker for the evaluation of ECRS severity. Furthermore, EDN induces production of MMP-9 from the nasal epithelium, which may be involved in the pathogenesis of ECRS.

The immunological basis of the clinical heterogeneity in autoimmune vasculitis remains poorly understood. In this study, we conduct single-cell transcriptome analyses on peripheral blood mononuclear cells (PBMCs) from newly-onset patients with microscopic polyangiitis (MPA). Increased proportions of activated CD14⁺ monocytes and CD14⁺ monocytes expressing interferon signature genes (ISGs) are distinctive features of MPA. Patient-specific analysis further classifies MPA into two groups. The MPA-MONO group is characterized by a high proportion of activated CD14⁺ monocytes, which persist before and after immunosuppressive therapy. These patients are clinically defined by increased monocyte ratio in the total PBMC count and have a high relapse rate. The MPA-IFN group is characterized by a high proportion of ISG⁺ CD14⁺ monocytes. These patients are clinically defined by high serum interferon-alpha concentrations and show good response to immunosuppressive therapy. Our findings identify the immunological phenotypes of MPA and provide clinical insights for personalized treatment and accurate prognostic prediction.

Mitochondrial DNA (mtDNA) leakage into the cytoplasm can occur when cells are exposed to noxious stimuli. Specific sensors recognize cytoplasmic mtDNA to promote cytokine production. Cytoplasmic mtDNA can also be secreted extracellularly, leading to sterile inflammation. However, the mode of secretion of mtDNA out of cells upon noxious stimuli and its relevance to human disease remain unclear. Here, we show that pyroptotic cells secrete mtDNA encapsulated within exosomes. Activation of caspase-1 leads to mtDNA leakage from the mitochondria into the cytoplasm via gasdermin-D. Caspase-1 also induces intraluminal membrane vesicle formation, allowing for cellular mtDNA to be taken up and secreted as exosomes. Encapsulation of mtDNA within exosomes promotes a strong inflammatory response that is ameliorated upon exosome biosynthesis inhibition in vivo. We further show that monocytes derived from patients with Behçet's syndrome (BS), a chronic systemic inflammatory disorder, show enhanced caspase-1 activation, leading to exosome-mediated mtDNA secretion and similar inflammation pathology as seen in BS patients. Collectively, our findings support that mtDNA-containing exosomes promote inflammation, providing new insights into the propagation and exacerbation of inflammation in human inflammatory diseases.

Objective: B-cell activating factor (BAFF) is implicated in SLE pathogenesis. Blocking BAFF signalling has contributed to reducing glucocorticoid dosage and preventing organ damage. However, clinical characteristics of patients who may benefit from this therapy are not yet fully elucidated. Therefore, we identified patients with high BAFF-bioactivity to investigate their clinical characteristics and BAFF-producing cells. Methods: We established the reporter cell for BAFF and investigated the clinical characteristics of SLE patients with high BAFF-bioactivity. We identified BAFF-expressing kidney cells using publicly available scRNA-seq data and immunohistological analysis. SLE patients were stratified based on the bioactivity of BAFF and type-I IFN (IFN-I) to identify associated characteristic clinical manifestations. Results: SLE patients, especially patients with LN, had significantly higher serum BAFF-bioactivity than healthy controls (HC) and non-LN patients. Additionally, single-cell-RNA-seq data and immunohistological analysis of kidney samples from LN patients revealed that BAFF is expressed in glomerular macrophages and mesangial cells. Notably, BAFF bioactivity was elevated in the urine of LN patients compared with that of non-LN patients, while no IFN-I bioactivity was detected in the urine. Furthermore, SLE stratification based on bioactivities of serum BAFF and IFN-I revealed the clinical characteristics of patients: high BAFF represented patients with LN and high IFN-I represented patients with blood and skin manifestations. Conclusions: Monitoring urinary BAFF-bioactivity may be valuable in diagnosing LN. Furthermore, stratification based on serum BAFF and IFN-I bioactivities may allow the identification of appropriate patients for biologics targeting BAFF and IFN-I.

Immune checkpoint inhibitors (ICIs) have caused revolutionary changes in cancer treatment, but low response rates remain a challenge. Semaphorin 4A (Sema4A) modulates the immune system through multiple mechanisms in mice, although the role of human Sema4A in the tumor microenvironment remains unclear. This study demonstrates that histologically Sema4A-positive non–small cell lung cancer (NSCLC) responded significantly better to anti–programmed cell death 1 (PD-1) antibody than Sema4A-negative NSCLC. Intriguingly, SEMA4A expression in human NSCLC was mainly derived from tumor cells and was associated with T cell activation. Sema4A promoted cytotoxicity and proliferation of tumor-specific CD8 ⁺ T cells without terminal exhaustion by enhancing mammalian target of rapamycin complex 1 and polyamine synthesis, which led to improved efficacy of PD-1 inhibitors in murine models. Improved T cell activation by recombinant Sema4A was also confirmed using isolated tumor-infiltrating T cells from patients with cancer. Thus, Sema4A might be a promising therapeutic target and biomarker for predicting and promoting ICI efficacy.

To identify the dynamics of neutrophil autoimmunity, here we focus on anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and perform single-cell transcriptome and surface proteome analyses on peripheral white blood cells from patients with new-onset microscopic polyangiitis (MPA). Compared with controls, two neutrophil populations, immature neutrophils and neutrophils with type II interferon signature genes (Neu_T2ISG), are increased in patients with MPA. Trajectory and cell–cell interaction analyses identify Neu_T2ISG as a subset that differentiates from mature neutrophils upon stimulation with IFN-γ and TNF, which synergize to induce myeloperoxidase and Fcγ receptors expression on the neutrophil cell surface and promote ANCA–induced neutrophil extracellular trap formation. Case-by-case analysis indicates that patients with a high proportion of the Neu_T2ISG subset are associated with persistent vasculitis symptoms. A larger cohort analysis shows that serum IFN-γ levels at disease onset correlate with susceptibility to disease relapse. Our findings thus identify neutrophil diversity at the single cell level and implicate a biomarker for predicting relapse in small vessel vasculitis.