Oropharyngeal candidiasis remains a significant health issue, especially among immunocompromised individuals, affecting mucosal tissues in the oral cavity and impairing quality of life. Despite the clinical importance of macrophages as first responders, the precise mechanisms enabling these cells to sense and counteract Candida infections at the molecular level have remained obscure. This study fills a critical knowledge gap by demonstrating that TREM2, a receptor known for sensing tissue damage in various pathological contexts, directly recognizes the fungal toxin candidalysin and orchestrates an effective antifungal response.

Employing cutting-edge single-cell transcriptomic sequencing, the research team meticulously mapped the immune landscape within the tongues of a murine OPC model. This approach revealed a pronounced infiltration of TREM2-expressing macrophages derived from monocytes localized in the infected lingual epithelium. Genetic ablation models, including global and myeloid lineage-specific knockouts of TREM2 as well as targeted depletion of TREM2-expressing cells via diphtheria toxin receptor approaches, definitively established the indispensable role of these macrophages in conferring resistance to OPC.

A pivotal and longstanding question in fungal immunology—how the host detects candidalysin—was expertly addressed through comprehensive biophysical and computational strategies. Surface plasmon resonance (SPR) and microscale thermophoresis (MST) assays unequivocally confirmed the binding of TREM2 to candidalysin. Further structural insights were gleaned through advanced AlphaFold molecular docking combined with site-directed mutagenesis, identifying key amino acid residues on TREM2 (D131, R136, P169) and candidalysin (G65, N73, N91-K92) that mediate this specific interaction. This discovery reveals how the host immune system cleverly co-opts a pathogen-derived toxin as an alarm signal, enhancing immunosurveillance and rapid response.

The signaling cascade triggered by TREM2 engagement with candidalysin is intricate yet effective. Upon toxin recognition, TREM2 recruits the adaptor protein DAP12 to initiate downstream signaling. This activation proceeds through Syk kinase phosphorylation, followed by phosphorylation of the transcription factor NF-κB p65 and the MAP kinase p38. Consequent to these events, macrophages secrete tumor necrosis factor-alpha (TNF-α), a cytokine that acts both autocrinely and paracrinely within the mucosal milieu.

Functionally, TNF-α promotes macrophage activities such as phagocytosis, microbial killing, and reactive oxygen species (ROS) generation, amplifying fungal clearance. Simultaneously, TNF-α enhances neutrophil extracellular trap (NET) formation and bactericidal functions, crucial defenses against secondary bacterial infections that often complicate fungal diseases. Moreover, TNF-α exerts a modulatory effect on IL-17 signaling pathways in TCRαβ+ T cells, underscoring its role in fine-tuning adaptive immune responses during fungal invasion.

This comprehensive elucidation of the TREM2–candidalysin–TNF-α axis underscores its central importance in early innate immunity against OPC, as it bridges the innate and adaptive arms of host defense. The findings dramatically advance our understanding of host-pathogen interactions and highlight the sophistication of immune sentinel cells in detecting molecular signatures of fungal virulence.

Translationally, the study offers exciting new avenues for therapeutic intervention. Targeting TREM2 with agonists or devising candidalysin mimetics could serve as novel strategies to boost local innate immunity, particularly valuable for patients with compromised immune systems, such as those undergoing CAR-T cell therapies or chemotherapy. Such approaches might potentiate the mucosal barrier’s resilience against opportunistic fungal infections.

Furthermore, the delineated epitope on candidalysin recognized by TREM2 represents a promising candidate for vaccine development, potentially inducing robust immune memory and long-lasting protection against Candida infections. Monitoring TREM2 and candidalysin expression levels in oral mucosa could also be harnessed diagnostically to predict patient susceptibility and guide personalized treatment strategies.

Professor Yunsheng Liang and colleagues’ work not only breaks new ground in fungal immunology but also exemplifies the power of integrative methods encompassing molecular biology, structural bioinformatics, and immunology. Their insights profoundly deepen our grasp of the innate immune system’s capacity to leverage pathogen-derived molecules for host protection and open pathways toward innovative antifungal therapeutics and diagnostics.

As fungal infections increasingly pose a threat globally amidst rising numbers of immunocompromised individuals, such cutting-edge research delivers hope for more effective management and prevention of these debilitating diseases. The TREM2 recognition mechanism of candidalysin establishes an elegant paradigm of immune vigilance, turning a microbial weapon into a trigger for host defense.

This landmark study thereby reframes our conceptual understanding of fungal pathogenesis and immunity, urging further exploration into TREM2’s roles across diverse infectious and inflammatory contexts and driving forward the frontier of translational immunology.

Subject of Research: Animals

Article Title: TREM2-mediated recognition of candidalysin by macrophages confers early protective innate immunity in oropharyngeal candidiasis

News Publication Date: 18-May-2026

References: DOI: 10.1007/s44466-026-00041-5

Image Credits: Professor Yunsheng Liang from Central South University, Professor Yingping Xu from Southern Medical University, Professor Xiaowen Wang from Peking University First Hospital

Keywords: Immunology, Infectious diseases, Fungal infections, Innate immunity, Signal transduction, Molecular biology, Host pathogen interactions, Biotechnology

The study centers on a unique population of intestinal T cells characterized by their lack of canonical markers CD4 and CD8αβ, yet expressing T-cell receptor αβ (TCRαβ). These CD4⁻CD8αβ⁻TCRαβ⁺ T cells defy previous categorization in the traditional T cell lineage dichotomy. The research demonstrates that these cells do not simply behave as immune effectors but function akin to antigen presenting cells (APCs), a role typically reserved for dendritic cells, macrophages, or B cells. This discovery was made feasible by advanced flow cytometry and single-cell transcriptomic analyses, which precisely mapped their phenotypic and functional properties.

T cell-mediated antigen presentation has been a contentious concept within immunology. While APCs are conventionally non-lymphoid cells tasked with priming naive T cells, this study identifies that a subset of intestinal T cells can themselves present antigen in a manner that promotes immune tolerance rather than immunity. These cells express key molecules associated with antigen processing and presentation pathways, including MHC class II, and costimulatory molecules with a profile consistent with supporting regulatory functions rather than proinflammatory responses.

Within the intestinal microenvironment, where tolerance to commensal microbiota and dietary antigens is essential to prevent chronic inflammation, these tolerogenic T cells appear critical. The gut’s immune system walks a razor’s edge, balancing defense against pathogens with tolerance toward harmless antigens. The identified cell population plays a pivotal role in this balancing act, contributing to the maintenance of immune homeostasis by presenting antigens in a way that promotes the generation and sustenance of regulatory T cells, thereby suppressing destructive immune responses.

One of the profound implications of this work is its potential impact on understanding inflammatory bowel diseases (IBDs) such as Crohn’s disease and ulcerative colitis. Dysregulated immune responses to gut antigens are hallmarks of these conditions. The newly described T cell population could represent a previously unrecognized target for modulating immune tolerance in the gut. Therapies aimed at enhancing the function or numbers of these tolerogenic T cells may ameliorate pathological inflammation characteristic of IBD.

At the molecular level, the study dissects the signaling pathways that govern the tolerogenic function of these T cells. Transcriptomic profiles reveal upregulation of genes involved in antigen processing and presentation, including invariant chain (CD74) and genes associated with the endosomal machinery essential for MHC class II loading. Additionally, these cells exhibit increased expression of immunomodulatory cytokines such as IL-10, known for its potent anti-inflammatory effects, further underlining their role in fostering a regulatory environment.

The identification of CD4⁻CD8αβ⁻TCRαβ⁺ T cells as functional APCs also raises fundamental questions about T cell plasticity and lineage commitment. Traditionally, mature T cells have been viewed as terminally differentiated effector or memory cells with fixed functions. However, this study reveals that even terminally differentiated T cell populations retain the capacity to undertake APC-like roles, probably adapting to specific microenvironmental cues typical of the intestinal mucosa.

Methodologically, this research leveraged state-of-the-art techniques including high-parameter flow cytometry, confocal microscopy, and single-cell RNA sequencing to characterize these T cells comprehensively. Functional assays demonstrated their ability to present antigen and stimulate regulatory T cell proliferation ex vivo, confirming their tolerogenic capacity. Mouse models deficient in these T cells exhibited heightened susceptibility to induced colitis, highlighting their protective role in gut inflammation.

Interestingly, the spatial distribution of these tolerogenic T cells within the intestinal tissue was elucidated through advanced imaging. They predominantly inhabit the lamina propria of the small and large intestine, strategically positioned to intercept antigens from the gut lumen and interact with other immune subsets. This physical localization emphasizes their integral role at the frontline interface between host immunity and external antigenic stimuli.

The discovery also prompts a reevaluation of gut-associated lymphoid tissue (GALT) function. Within Peyer’s patches and isolated lymphoid follicles, these T cells may provide a unique antigen-presenting niche that fine-tunes mucosal immune responses. This discovery suggests that immune tolerance in the gut involves more cellular actors than previously appreciated, with non-classical T cells contributing significantly to the antigen presentation landscape.

From a therapeutic standpoint, harnessing these T cells could lead to innovative immunotherapies. Enhancing their tolerance-inducing capacities may have applications beyond the gut, potentially influencing systemic autoimmune diseases and transplant rejection scenarios where unwanted immune activation is a major concern. Conversely, aberrations in their function may contribute to immunodeficiencies or failure to control intestinal inflammation, offering diagnostic and prognostic insights.

Furthermore, this research underscores the dynamic interplay between the intestinal microbiota and host immunity. The tolerogenic T cells may sense microbial metabolites or antigens, translating these signals into regulatory cues that maintain symbiosis within the gut. Understanding these interactions at a molecular level could unveil new microbial targets to augment or restore immune tolerance through diet or probiotic interventions.

In conclusion, this study significantly expands the paradigm of immune regulation in the gut by revealing a previously unappreciated population of intestinal T cells capable of presenting antigens and fostering tolerance. It marks a pivotal advance in mucosal immunology, with far-reaching implications for basic science and clinical applications. Future research will undoubtedly explore the developmental origins of these cells, their relevance in human diseases, and their potential exploitation for therapeutic benefit, offering hope for improved management of autoimmune and inflammatory conditions.

Nemoto and colleagues’ breakthrough provides not only novel insights into the cellular complexity of the intestinal immune system but also reinforces the importance of context-dependent immune functions of T cells. By combining cellular phenotyping with functional validation and in vivo relevance, this research sets a new benchmark for dissecting immune regulatory networks at mucosal surfaces, shining a light on how immune tolerance is orchestrated at the cellular level.

The implications extend beyond intestinal immunology, hinting at similar tolerogenic T cell subsets in other tissues where immune tolerance is critical, such as the skin or lungs. As the field explores these possibilities, the concept of T cells transcends their classical roles, embracing a more versatile identity that adapts to the immune system’s ever-changing needs.

This discovery also challenges immunologists to rethink the hierarchy of antigen-presenting cells and highlights an unexpected plasticity in the immune compartment. Understanding how environmental, microbial, or nutritional factors modulate these tolerogenic T cells could unlock strategies to engineer immune tolerance in various pathological contexts.

Ultimately, by bridging innate and adaptive immune features within a single cell type, these intestinal CD4⁻CD8αβ⁻TCRαβ⁺ T cells embody the sophistication of mucosal immunity. As research progresses, harnessing their unique properties promises to transform therapeutic approaches to chronic inflammation, autoimmunity, and perhaps even cancer, ushering in a new era of precision immunology centered on immune tolerance.

Subject of Research: Intestinal immunology, T cell subsets, immune tolerance, antigen presenting cells, murine gut mucosa.

Article Title: Intestinal CD4⁻CD8αβ⁻TCRαβ⁺ T cells function as tolerogenic antigen presenting cells in mice.

Article References:
Nemoto, Y., Morikawa, R., Yonemoto, Y. et al. Intestinal CD4⁻CD8αβ⁻TCRαβ⁺ T cells function as tolerogenic antigen presenting cells in mice. Nat Commun 16, 7072 (2025). https://doi.org/10.1038/s41467-025-62089-y

Image Credits: AI Generated

The study meticulously compares the adaptive immune responses, particularly T cell dynamics, elicited by repeated controlled human infections with those arising from chronic, naturally acquired schistosome exposure. The experimental design employed a highly controlled infection model, allowing for precise measurement of T cell phenotypes and functions across multiple exposure events. This approach provided a rare window into how immunological memory and effector functions evolve in response to persistent antigen stimulation.

Central to the investigation were multiple subsets of T cells, including central memory, effector memory, and regulatory populations, each playing distinct roles in the host defense and immunopathology. Utilizing state-of-the-art flow cytometry and single-cell transcriptomics, the researchers delineated how repeated infections modulate the balance between protective immunity and immune regulation. Notably, the controlled model revealed that repeated schistosome exposure induces a potent, yet finely tuned, T cell response characterized by sustained activation without overt exhaustion.

This nuanced immune activation contrasts strikingly with the T cell profiles observed in individuals with natural, chronic infections, where prolonged antigen presence often leads to functional impairment or “exhaustion” of T cells. The study found that natural exposure tends to skew the immune landscape towards a more regulatory and less inflammatory milieu, arguably a survival adaptation that limits tissue damage while allowing parasite persistence.

Importantly, the research highlights the role of T helper 1 (Th1) and T helper 2 (Th2) cells in orchestrating the immune response. While Th2 responses have traditionally been linked to anti-schistosome immunity and granuloma formation around eggs, this study reveals that repeated controlled infections sustain a mixed Th1/Th2 environment. Such a balanced cytokine landscape may optimize parasite clearance while mitigating pathological consequences, an insight with direct implications for vaccine strategies aiming to mimic natural but protective immunity.

Delving deeper, the authors explore how regulatory T cells (Tregs) expand in response to continuous antigenic stimulation, potentially tempering the immune response to avoid excessive inflammation. However, excessive Treg activity in chronic natural infections may impede effective parasite clearance. The controlled infection model thus serves as a powerful system to dissect the thresholds at which immune modulation shifts from beneficial to detrimental, a crucial consideration for therapeutic targeting.

Beyond classical T cell subsets, the study also investigates the emerging roles of tissue-resident memory T cells (Trm), revealing their accumulation and retention in affected tissues upon repeated exposure. These cells may provide a localized, rapid response to reinfection, highlighting an underexplored axis of immunity in schistosomiasis. Their presence and functionality in humans, confirmed through detailed immunophenotyping, underscore the complexity and compartmentalization of the immune response in helminth infections.

The detailed kinetic analyses carried out demonstrate that each round of infection and treatment modulates T cell receptor (TCR) repertoires, suggesting that clonal selection and expansion processes evolve dynamically with repeated antigen encounters. This phenomenon not only shapes the quality of the immune response but also influences the breadth and durability of protective immunity, a critical factor for designing enduring vaccines.

Additionally, the role of co-inhibitory molecules such as PD-1 and CTLA-4 was examined, revealing their elevated expression in naturally infected individuals compared to the controlled infection group. These molecules typically mark cellular exhaustion states, providing an immunological checkpoint that may be co-opted by schistosomes to evade immune destruction. Modulating these pathways could enhance therapeutic efficacy, a promising avenue for future clinical studies.

The researchers also underscore the importance of applying controlled human infection models in parasitology, a field traditionally reliant on observational studies in endemic settings. By limiting variables and precisely timing infection events, this methodology allows robust conclusions about causality in immune regulation, setting a new standard for helminth immunology research.

Significantly, the study provides a rich dataset integrating immunophenotyping, transcriptomic profiling, and functional assays, offering a holistic view of T cell dynamics. This comprehensive approach reveals previously unrecognized populations and states of T cells that can now be targeted for improved immunomodulation in schistosomiasis. The implications extend beyond schistosomes, shedding light on general principles of immune adaptation to chronic infections.

Moreover, these insights have profound implications for vaccine development, as they identify specific immune signatures associated with protective immunity versus susceptibility or pathology. Designing vaccines that elicit balanced Th1/Th2 responses, promote durable effector memory, and avoid premature exhaustion could revolutionize schistosomiasis control, a necessity given the limitations of current chemotherapy-based strategies.

The study also touches upon the potential impact of host genetics and environmental factors in shaping immune responses, although these were beyond the direct scope of the current work. Nevertheless, the standardized infection model paves the way for future investigations into personalized immunotherapies and the role of microbiome interactions in helminth infections.

In conclusion, this research not only elucidates the complex interplay between repeated schistosome infections and adaptive immunity but also exemplifies how cutting-edge immunological tools and controlled human models can accelerate understanding of neglected tropical diseases. By uncovering the detailed choreography of T cells in different exposure scenarios, the study opens new horizons for interventions that harness the immune system’s full potential to combat parasitic infections effectively and safely.

The findings are poised to inspire a paradigm shift in schistosomiasis research, encouraging the integration of controlled infection trials with molecular immunology to unravel host-pathogen interactions. As schistosomiasis remains a major global health burden, the insights gained here bring hope for innovative solutions that could tip the balance in favor of durable immunity and disease elimination.

Subject of Research: T cell immune responses to repeated controlled human schistosome infection versus natural exposure

Article Title: T cell responses in repeated controlled human schistosome infection compared to natural exposure

Article References:
Driciru, E., Koopman, J.P.R., Steenbergen, S. et al. T cell responses in repeated controlled human schistosome infection compared to natural exposure. Nat Commun 16, 6827 (2025). https://doi.org/10.1038/s41467-025-62144-8

Natural killer cells, vital components of the innate immune system, are renowned for their ability to target and destroy malignant cells without prior sensitization. Despite their importance, understanding the nuanced behavior and adaptation of NK cell subsets in the context of CLL, especially after targeted therapies like ibrutinib, has remained elusive. This research bridges that knowledge gap by delivering a nuanced portrayal of NK cell diversity, function, and molecular underpinnings in disease progression and therapy response.

Researchers collected peripheral blood samples spanning a spectrum of clinical stages, including individuals with monoclonal B-cell lymphocytosis (MBL), newly diagnosed CLL (ND-CLL), and those who had undergone ibrutinib treatment achieving complete or partial responses. Additionally, samples from patients suffering from Richter’s syndrome—a highly aggressive transformation of CLL—were included to provide a comprehensive overview of NK cell behavior in varying disease contexts. This heterogeneous sample set allowed for an in-depth comparative analysis of NK cell subset evolution.

The team harnessed single-cell RNA sequencing technologies to profile the transcriptomes of individual NK cells extracted from patient blood samples. This granular approach enabled precise identification of cellular subsets, their gene expression patterns, and the dynamic shifts occurring in response to therapeutic intervention. Furthermore, the researchers implemented pseudotemporal analysis — a computational technique that orders cells along an inferred developmental or differentiation trajectory — to elucidate the temporal dynamics and lineage relationships of NK cell subsets post-ibrutinib.

Three distinct NK cell subsets emerged from this exhaustive profiling: CD56^bright NK cells, typically associated with immune regulation and cytokine production; CD56^dim NK cells, known for their cytotoxic prowess; and a novel, highly cytotoxic subset uniquely enriched in CLL patients, designated as CLL_NK cells. This newly characterized CLL_NK subset demonstrated a pronounced gene expression signature indicative of specialized functional roles, setting it apart from conventional NK populations.

To uncover crucial genes driving the biology of the CLL_NK subset, the authors employed Mendelian randomization and genomic colocalization analyses—statistical genetics methods that integrate genetic association data to infer causality and pinpoint gene-trait linkages. Such analyses yielded a core set of key genes underpinning the function and expansion of the CLL_NK compartment, thereby illuminating molecular targets with potential therapeutic relevance.

Capitalizing on the discovery of these core genes, the researchers developed a novel cell subset-specific index, termed the CLL_NK Index (CNI), designed to quantify and predict patient responses to immunotherapy. This index not only reflects the abundance and activity of the CLL_NK subset but also serves as a biomarker framework for stratifying patients based on predicted treatment outcomes, thus promising improved personalized therapy.

Beyond genetic profiling, a battery of immune infiltration algorithms were applied to assess the interplay between NK subsets and the broader immune microenvironment within CLL. This integrative analysis uncovered complex regulatory networks and highlighted the critical influence of the CLL_NK subset in modulating immune surveillance and evasion mechanisms, which are pivotal challenges in effective leukemia treatment.

To propel translational potential, the study incorporated drug sensitivity assays combined with molecular docking simulations, aiming to identify compounds capable of modulating NK cell activity or directly targeting malignant B cells. This comprehensive pipeline highlighted semaxanib and ulixertinib as promising candidates, enriching the therapeutic arsenal against CLL. Semaxanib, primarily an angiogenesis inhibitor, and ulixertinib, an ERK1/2 kinase inhibitor, may synergistically augment immune-mediated clearance of leukemic cells by optimizing NK cell functionality.

Crucially, this work underscores the dynamic plasticity of NK cell populations under the selective pressure of ibrutinib therapy. The expansion and functional recalibration of the CLL_NK subset reflect adaptive immune remodeling, which can either facilitate therapeutic success or contribute to resistance mechanisms. Understanding this delicate balance offers new avenues to enhance the efficacy of existing treatments or design novel immunomodulatory strategies.

Moreover, the single-cell transcriptomic approach adopted provides an unprecedented resolution into cellular heterogeneity, unveiling fine-grained molecular features that bulk RNA sequencing methods often obscure. This technological advancement illuminates the complexity of immune cell landscapes in cancer and exemplifies the potential of precision immunology to revolutionize clinical oncology, particularly in indolent but treatment-resistant malignancies like CLL.

The implications of these findings are profound. By mapping NK cell behaviors, identifying key genetic drivers, and linking these elements to clinical outcomes, the study sets the stage for integrating NK cell signatures into routine prognostic and therapeutic frameworks. Such integration heralds a future where monitoring immune cell subsets could guide real-time treatment decisions, tailoring interventions to the evolving immune milieu within individual patients.

Importantly, this research also signals the vital need to consider immune system components beyond the traditionally studied T and B lymphocytes. NK cells, often underappreciated in the context of CLL, now emerge as pivotal players capable of influencing disease course and therapeutic responsiveness. Unlocking their full potential could transform the landscape of immunotherapy for hematologic cancers.

As the field moves forward, further studies are needed to validate the CNI in larger, multicenter cohorts and to explore how modulating the CLL_NK subset might synergize with other treatment modalities, including checkpoint inhibitors and CAR-NK therapies. Such efforts could amplify anti-leukemic immune responses, minimizing relapse and improving long-term survival.

In summary, this landmark research unravels the complex NK cell subset dynamics and their molecular circuits following ibrutinib therapy in CLL, charting a path toward more refined, immune-informed therapeutic strategies. It illuminates the promise of integrating advanced single-cell analyses with genetic epidemiology and computational drug screening to revolutionize cancer care.

Subject of Research: Investigation of NK cell subsets and specific gene signatures dynamics post-ibrutinib therapy in chronic lymphocytic leukemia using single-cell transcriptomics.

Article Title: Unravelling NK cell subset dynamics and specific gene signatures post-ibrutinib therapy in chronic lymphocytic leukaemia via single-cell transcriptomics

Article References:
Liu, C., Ding, T., Zou, R. et al. Unravelling NK cell subset dynamics and specific gene signatures post-ibrutinib therapy in chronic lymphocytic leukaemia via single-cell transcriptomics. BMC Cancer 25, 745 (2025). https://doi.org/10.1186/s12885-025-14166-0

Image Credits: Scienmag.com

DOI: https://doi.org/10.1186/s12885-025-14166-0