The lung immune system is uniquely adapted to sustain continuous exposure to environmental stimuli while avoiding excessive inflammation. Among lung-resident immune cells, alveolar macrophages are well recognized as key regulators of immune quiescence and tissue homeostasis under steady-state conditions. In contrast, the roles of dendritic cells (DCs), another population of resident immune cells, have received comparatively less attention, likely owing to their lower abundance within the lung tissue. Nevertheless, as professional antigen-presenting cells and central orchestrators of adaptive immunity, DCs are critically positioned to determine the balance between immune tolerance and activation in the lung. Recent studies have increasingly highlighted the contribution of lung DCs to the pathogenesis of inflammatory and neoplastic lung diseases, including allergy, asthma, and cancer. However, how DCs are positioned, conditioned, and functionally regulated under steady-state conditions remains incompletely understood. In this review, we focus on spatial organization, cellular interactions, and microenvironmental cues that shape lung DC behavior at steady-state and delineate how these homeostatic programs preserve immune tolerance while maintaining immune readiness.
T cell-based universal influenza vaccines aim to generate robust lung-resident memory CD8+ T cells (TRM), yet it remains unclear whether conserved Ags elicit equally protective TRM pools. We compared recombinant adenoviral vectors expressing the influenza A nucleoprotein (rAd/NP) or polymerase basic protein 1 (PB1). After intranasal immunization, both induced comparable magnitudes of respiratory Ag-specific CD8+ T cells, yet only rAd/NP provided 100% survival after lethal influenza challenge. This disparity reflected qualitative differences in the TRM pool; nucleoprotein (NP)-specific cells were predominantly CD103-CD49a+, a phenotype associated with superior cytotoxicity, whereas PB1-specific cells were mainly CD103+CD49a-. Furthermore, NP-specific CD8+ T cells showed 100-fold higher functional avidity and stronger lung-local CTL activity than PB1-specific cells. Our findings demonstrate that TRM quality-specifically phenotypic bias and functional avidity-rather than magnitude, are the primary determinants of vaccine-mediated protection. This study underscores the critical importance of Ag selection in optimizing T cell-based universal vaccine strategies.
Mitochondria have long been viewed as the "powerhouses" of the cell, but research over the past decade has established that they play a far more complex role in skin immune homeostasis beyond ATP production. The metabolic preferences of immune cells and skin parenchymal cells-glycolysis, oxidative phosphorylation, or fatty acid oxidation-determine their fate choices during inflammatory responses. When mitochondrial function is impaired, the release of damage-associated molecular patterns (DAMPs) such as mitochondrial DNA and mitochondrial ROS can activate the cGAS-STING and NOD-like receptor family pyrin domain-containing 3 inflammasome pathways, driving inflammatory cycles in various skin diseases including psoriasis, atopic dermatitis, lupus erythematosus, and vitiligo. This review systematically examines the key mechanisms of mitochondrial metabolic reprogramming in skin immune disorders, focusing on 3 typical scenarios: the metabolic preferences of immune cells, mitochondrial DAMP-mediated autoinflammation, and the impact of mitochondrial dynamics imbalance on tissue-resident memory T cell function. Furthermore, we evaluate clinical evidence for repurposing old drugs such as metformin and thiazolidinediones, and discuss the translational prospects of emerging strategies including Nrf2 agonists, mitophagy inducers, and targeted nanocarriers. Understanding the "dual identity" of mitochondria in skin immunity-as both metabolic regulators and signaling sensors-will lay the foundation for developing precise metabolic immunomodulatory therapies.
Neutrophils serve host defense through phagocytic activity in acute kidney injury. However, excessive neutrophil activation drives tissue damage during systemic inflammation. NOD-like receptor family pyrin domain-containing 3 (NLRP3) has been reported to regulate neutrophil function in inflammatory conditions, but it remains unclear how NLRP3 modulates neutrophil function in the kidney. We investigated the role of NLRP3 in regulating neutrophil phagocytic activity and infiltration in the kidney. Nlrp3 knockout (KO) and Nlrp3 KO/lysozyme M-GFP mice were analyzed by time-lapse imaging and intravital imaging under naïve and LPS-treated conditions. Nlrp3 KO neutrophils exhibited enhanced motility and phagocytic activity against pHrodo+ Escherichia coli particles. The enhanced phagocytic activity was confirmed at both cellular and tissue levels in Nlrp3 deficient kidneys in vivo. Nlrp3 deficient kidneys showed increased neutrophil infiltration accompanied by upregulation of Cxcl2 and Cxcr2 and downregulation of Cxcl12 and Cxcr4 under naïve and LPS-treated conditions. Despite increased infiltration, Nlrp3 deficient kidneys under LPS treatment displayed reduced Il1b and Il6 expression and attenuated tissue damage. Collectively, these findings suggest that NLRP3 suppresses neutrophil effector function at the cellular level. At the tissue level, NLRP3 amplifies inflammatory tissue injury in the kidney.
Seasonal influenza evades vaccine-induced immunity via ongoing antigenic drift, highlighting the critical necessity for universal vaccines that elicit broadly cross-reactive CD8+ T cell responses targeting conserved internal viral epitopes. In pursuit of this objective, we prepared biocompatible and biodegradable poly(lactic-co-glycolic acid) (PLGA) nanocarriers (NCs) and functionalized them with MHC-I molecules. Among various murine and human epitopes tested, PB1703-711 and M158-66 showed the highest stabilization of H-2Kb and HLA-A2.1 molecules, respectively, thereby promoting sustained Ag presentation. These NCs exhibited specific peptide-loading onto MHC-I molecules while minimizing non-specific peptide surface binding. In vivo immunization of C57BL/6 mice with PB1703-711-loaded NCs elicited epitope-specific CD8+ T cell responses. Furthermore, the successful specific peptide-loading of HLA-A2.1-attached NCs highlighted the system's human translational applicability. Ultimately, by combining effective Ag delivery with specific CTL induction, this designed NC platform provides a promising strategy for developing next-generation universal vaccines.
Cancer immunotherapy has reshaped oncology, largely through immune checkpoint inhibitors that release the brakes on tumor-reactive T cells. Yet the benefit remains uneven, and that unevenness traces back to a few basic biological limits. Checkpoint blockade amplifies immunity that is already present; it does not create tumor specificity de novo. Poor Ag quality, defective Ag presentation, a suppressive microenvironment, and epigenetically fixed T-cell exhaustion together set a ceiling on what checkpoint release can achieve. Next-generation strategies try to move past these limits by reorganizing immunotherapy around the functional layers of the immune response. Cancer vaccines define tumor-specific neoantigens and expand the responses against them. Ab-based approaches tune inhibitory signaling, draw immune cells toward the tumor, and trigger immunogenic cell death. Cellular therapies-chimeric Ag receptor T cell, TCR-engineered T cells, and tumor-infiltrating lymphocytes (TILs)-boost effector potency, with TIL therapy notable for preserving tumor-reactive repertoires shaped in vivo. Rather than rivals, these modalities are best seen as complementary layers-Ag definition, immune priming, effector optimization, and microenvironmental conditioning-to be combined in a programmable way. As genomic profiling, immunopeptidomics, and high-dimensional immune monitoring mature, the field is shifting from checkpoint-centered release toward precision immunoengineering, in which tumor-specific immunity is deliberately designed, aligned, and sustained.
Apoptotic cells are removed by efferocytosis, raising the possibility that in vivo apoptotic cell frequencies underestimate cell death. Rosa26-INDIA is an apoptosis reporter that detects activated caspase-3 (Casp3) via Förster resonance energy transfer (FRET) loss, but the relationship between Casp3 activation, phosphatidylserine exposure, membrane permeabilization, and efferocytic clearance remains unclear. We combined live-cell imaging and macrophage depletion to evaluate apoptotic B cell detection by Rosa26-INDIA. Live-cell imaging revealed that FRET loss preceded loss of detectable INDIA, Annexin-V positivity, and DAPI uptake. Loss of detectable INDIA occurred on average 6 and 12 min before Annexin-V and DAPI positivity, respectively, indicating that Rosa26-INDIA preferentially identifies early apoptotic cells. Consistently, macrophage depletion had limited effects on Rosa26-INDIA-based detection of apoptotic B cells under both steady-state and dexamethasone-induced conditions. These findings demonstrate that Rosa26-INDIA reports early apoptosis and suggest that macrophage-mediated efferocytosis does not substantially limit Rosa26-INDIA-based detection of apoptotic B cells under the conditions examined.
Aging involves progressive declines in lung structure and immune function, increasing the incidence and severity of respiratory diseases and reducing vaccine responsiveness. Meanwhile, the respiratory tract harbors a dynamic microbial ecosystem that contributes to immune homeostasis and colonization resistance. Growing evidence indicates that aging disrupts this host-microbe balance within the respiratory tract; however, the mechanisms and therapeutic implications remain incompletely integrated. This review summarizes age-related remodeling of the respiratory microbiome. Beyond compositional shifts, aging alters microbial functions, including metabolic output and resilience to perturbation, exhibiting downstream effects on epithelial barriers, mucus clearance, and immune priming. Furthermore, as the microbiome-immune axis is modifiable, microbiome-targeted therapies represent key opportunities to restore respiratory homeostasis during aging. These interventions, combined with senescence- and cytokine-directed immunomodulation and vaccine optimization using adjuvants and mucosal immune-informed designs, may reduce infection burden and chronic lung disease progression in older populations. Together, this review highlights that a deeper understanding of age-related respiratory microbiome remodeling and its interplay with immunosenescence will be essential for the rational design of microbiome-informed therapies.
Exhaustion of antiviral immunity driven by inhibitory signals is one hallmark of persistent viral infection. Notably, PD-1 and IL-10 are two major contributors to CD8+ T cell dysfunction. How these molecules are specifically induced during chronic viral infection remains mainly unknown. Using the lymphocytic choriomeningitis virus model, we show that the apoptotic-cell accumulation and expression of tyrosine kinase Mertk are linked to the outcome of chronic viral infection. Early CD8+ T cell activation correlated with increased dead-cell deposition, rapid induction of IL-10 and TGF-β in macrophages and dendritic cells (DCs), and a pronounced upregulation of PD-1 on CD8+ T cells and its ligand PD-L1. In TCR-β-deficient mice lacking CD8+ T cells, dead-cell generation and expression of IL-10, TGF-β, PD-1, and PD-L1 were markedly restricted. Our findings suggest that CD8+ T cell-mediated killing of infected targets generates large quantities of apoptotic cells, which activate the phosphatidylserine-binding kinase Mertk on macrophages and DCs. This signalling cascade subsequently promotes expression of IL-10, TGF-β, PD-1, and partially PD-L1. Consistent with this model, loss of Mertk in Mertk-/- mice reduced inhibitory cytokines and PD-1 expression, accelerated antiviral CD8+ T cell responses, and improved viral control. Collectively, our study provides important insight into cellular basis of T cell regulation identifying apoptotic cells and Mertk activation as key mechanisms initiating the suppression of CD8+ T cell immunity during chronic viral infection.
IgE plays a central role in allergic diseases by binding to specific allergens and triggering the release of inflammatory mediators from mast cells and basophils. Conventionally, allergen-specific IgE is generated by T-cell-dependent mechanisms in which IL-4-producing CD4+ T helper cells, including Th2 cells and T follicular helper cells, orchestrate B cell class switch recombination to IgE. However, elevated IgE levels are also observed in diverse contexts, including primary immunodeficiencies and inflammatory conditions, where allergen involvement is less clear, suggesting the existence of additional pathways for IgE biogenesis. Supporting this notion, recent studies have identified alternative routes in which innate immune cells such as basophils or group 2 innate lymphoid cells provide bystander IL-4 to drive the production of IgE. In this review, we provide a comprehensive overview of IgE production pathways and examine how they operate across physiological and pathological conditions. Recognizing this mechanistic diversity will deepen our understanding of IgE biology beyond its role in allergy, highlighting its multifaceted contributions to barrier defense, protective immunity, and the pathogenesis of various inflammatory disorders.
Immune cell states are not fixed. Rather, they emerge from dynamic transcriptional programs shaped by genetic variation, cellular context, and gene regulatory networks (GRNs). Single-cell and multi-omic technologies now enable population-scale immune profiling across molecular layers, revealing that cell-to-cell transcriptional variability is a functional feature that diversifies immune responses. Distribution-aware and tensor-based analytical frameworks capture this variability beyond mean expression, resolving coordinated gene programs across cell types, individuals, and conditions. Integrating human genetics with single-cell genomics demonstrates that genetic effects on gene expression, splicing, and chromatin accessibility are highly dependent on cell type, activation state, and differentiation trajectory. These variant-level signals converge on GRNs in which key transcription factors orchestrate context-dependent immune programs. High-throughput perturbation screens enable scalable functional validation of these networks, linking genetic variation to cellular function. Together, these integrative approaches translate molecular discoveries into clinical applications, from patient stratification to therapeutic target prioritization. Emerging spatial multi-omics and in situ perturbation screens further resolve neighbor-dependent regulation within intact tissue niches, offering a path from variant to mechanism to clinical translation.
Staphylococcus aureus (SA) colonization and cigarette smoking are both implicated in the pathogenesis of chronic airway disease, yet their combined effects on epithelial responses remain unclear. We investigated transcriptomic changes in human bronchial epithelial cells (BEAS-2B) following co-exposure to SA and cigarette smoke extract (CSE). RNA sequencing revealed that combined SA+CSE co-exposure was associated with a marked increase in differentially expressed genes, compared with single exposures. Functional enrichment and network analyses identified significant activation of pathways related to neutrophil migration, extracellular matrix remodeling, and inflammatory cascades, including TNF and IL-17 signaling. Key hub genes, notably CCL20, CXCL1, CXCL8, and IL-24, showed marked synergistic upregulation, which was validated by quantitative RT-PCR. These findings suggest that SA and cigarette smoke co-exposure is associated with a transcriptomic profile suggestive of neutrophilic inflammation. The involvement of IL-24 and IL-17 signaling suggests potential pathways linking bacterial colonization and smoking to airway inflammation and remodeling.
Respiratory syncytial virus (RSV) is a contagious pathogen that infects respiratory epithelial cells and causes serious lower respiratory diseases in young children and the elderly. In this study, we evaluated the cross-protective efficacy of intranasally administered virus-like particles (VLPs) expressing the prefusion (pre-F) conformation of the RSV A2 fusion protein against RSV B challenge. The VLPs displayed higher reactivity against pre-F site Ø-specific mAbs, compared to the formalin-inactivated RSV vaccines. Intranasally administered pre-F VLPs vaccine induced a Th1-biased immune response in both local and systemic compartments. In the systemic compartment, it elicited a high IgG2a/IgG1 ratio in sera and strong IFN-γ production by splenic cells, reflecting a robust Th1-type systemic immune activation. It promoted significantly increased IgA levels in bronchoalveolar lavage fluid and lung tissues. Furthermore, no significant histopathological lesions were observed in the lungs of RSV A2-derived pre-F VLPs immunized mice compared to FI-RSV vaccinated mice. These results highlight the relevance of intranasal RSV A2-based pre-F VLP immunization in eliciting cross-protection against RSV B while minimizing the risk of vaccine-associated enhanced respiratory disease (VERD). Therefore, RSV A2-derived pre-F VLPs can be a potential safe and effective nasal vaccine candidate against RSV B infection by inducing Th1-skewed immune responses and reducing the risk of VERD.
The lymphatic system is a highly branched endothelial tubular network that facilitates the migration of immune cells from the peripheral tissues to lymph nodes (LNs) and other lymphoid organs. Complement factors are essential for innate and adaptive immune functions. Complement anaphylatoxin C5a is crucial in vascular endothelial cell activation and lymphocyte polarization. Understanding the impact of C5a and its cognate receptor C5ar1 signaling on lymphatic function could provide new insights into the mechanisms of immune dysregulation observed in chronic inflammatory diseases. We demonstrate that acute C5a challenge in wildtype C57B6/J mice significantly reduced lymph propulsion compared to their C5ar1-deficient counterparts. C5ar1-dependent attenuation of lymph propulsion with LPS challenge corroborated with significantly increased endothelial-derived inducible nitric oxide synthase (iNOS) expression. C5ar1-iNOS axis modulated T helper cell polarization towards Cd4+/Ccr5+ Th1 subtypes, indicating that C5a-activated endothelialiNOS may contribute to Th1 polarization in the peripheral LNs during homing. Finally, we observed C5a-mediated endothelial surface glycoprotein CD146 interaction with Th1 cell intermediate filament protein vimentin that may facilitate transmigration of activated Th1 cells into systemic circulation and tissue interstitium. Given the critical role of the C5a/C5ar1 axis in promoting lymphatic dysfunction, our study highlights the therapeutic potential of targeting C5ar1 in chronic inflammatory conditions.
Cigarette smoke broadly affects the immune system, but the mechanisms by which it disrupts lung innate immunity and impairs macrophage-mediated homeostasis in healthy individuals remain unclear. This study investigates airway inflammation induced by chronic cigarette smoke extract (CSE) exposure by profiling pulmonary macrophages. CSE was generated by bubbling smoke from ten Marlboro cigarettes into 10 ml PBS to obtain 100% CSE, and C57BL/6 mice received 10% CSE intranasally 3 times per week for 4 wk. Chronic CSE exposure induced neutrophilic airway inflammation and augmented pulmonary Th17 and Th1 responses. Among macrophage subsets, CSE exposure promoted the expansion of CD11c+CD11b- alveolar macrophages (AMs) and upregulated IL-17A across macrophage subsets in lung tissue. In the lung, epithelial-derived IL-33 was significantly increased and was associated with enhanced IL-33/ST2 axis activity in IL-17A+ macrophages. In AMs, sequential CSE and IL-33 stimulation significantly increased ST2 expression and an IL-33/ST2-mediated pro-inflammatory response marked by elevated IL-6. Moreover, CSE exposure reprogrammed AMs with enhanced MAPK and NF-κB signaling. Notably, IL-33-stimulated macrophages after CSE exposure skewed naive CD4+ T cells toward Th17 differentiation. These findings suggest that CSE-activated, IL-33/ST2-driven pro-inflammatory macrophages drive neutrophilic inflammation and Th17 skewing, linking innate and adaptive immune responses in airway inflammation.
Adaptive-like functions of NK cells have been extensively studied in the context of human cytomegalovirus (HCMV) infection, particularly for NKG2C+ NK cells. The NKG2A inhibitory and the NKG2C activating receptors share a common ligand, the HLA-E molecule, and can be co-expressed in a unique NK cell subset. However, key characteristics and memory response capacity of this subset remain unclear. We analyzed the proliferative responses, functional attributes and transcriptional signatures of NKG2C+NKG2A+ subsets within CD57+ and CD57- fractions of peripheral blood CD56dimNK cells by comparing them with NKG2A- counterparts. Double-positive NK cells displayed a less mature phenotype, increased MHC-II and exhibited transcriptome profile indicating enhanced adhesion/migration capacities with no difference in adaptive state associated genes expression. These cells showed enhanced proliferation compared to NKG2A- cells, which was not reduced upon interaction with HLA-E presenting the HCMV (VMAPRTLFL, LFL) peptide. CD57+NKG2C+NKG2A+ subset showed enhanced antibody-dependent IFNγ production. Expanded upon LFL stimulation this subset again exhibited enhanced IFNγ production capacity along with peptide-specific mRNA expression profile, demonstrating an adaptive-like response. These results provide additional insight into the diversity of HCMV-specific NK cell subsets, highlighting NKG2A+NKG2C+ NK cells' immunotherapeutical potential.
Lupus nephritis (LN) is a critical manifestation in systemic lupus erythematosus. However, there has been little progress in treatment outcomes, and the discovery ofrobust and clinically relevant molecular subtypes would be informative for guiding stratified therapy for LN. Glomerular transcriptomic datasets of LN were obtained from publicly repositories. We investigate the molecular heterogeneity of LN by analyzing renal glomerular transcriptomic data from 135 patients with LN using integrated optimal algorithms and propose a refined two-molecular subtype scheme for LN (designated GC1 and GC2). GC1 represents an active form of LN enriched by IFN signaling pathways, Fc receptor-mediated signals, and neutrophil activation-associated processes. In contrast, GC2 is a subset characterized by class A/1(rhodopsin-like) and B cell (BC) receptor signaling pathways. The communication probability by receptor-ligand pairs is highly scored between BCs, CD4+ T cells and macrophages/monocytes. Proteinuria and renal insufficiency were more significant in GC1. We identified PIK3R2 as a hidden regulator in the disease module, and inhibition of PI3K subunits showed promising efficacy in counteracting altered molecular signatures in an active state of LN. The proposed two-molecular subtype scheme offers novel insights into the divergent mechanistic features of LN and represents a critical step toward precision medicine for LN.
