bims-traimu Biomed News
on Trained immunity
Issue of 2025–10–12
seven papers selected by
Yantong Wan, Southern Medical University



  1. Sci Rep. 2025 Oct 06. 15(1): 34698
      Bacillus Calmette-Guérin (BCG) has multiple heterologous off-target effects which extend beyond tuberculosis (TB) prophylaxis, which include protection against other non-tuberculous infections, autoimmune diseases, and tumor development. These heterologous effects are at least partially mediated by induction of trained immunity. In this study, we aimed to investigate the impact of IFNγ production capacity on induction of trained immunity in human volunteers vaccinated with BCG. We evaluated inflammation and immune activation-specific cytokine responses (IFNγ, TNF, IL-1, and IL-6) in PBMCs isolated from 323 healthy volunteers vaccinated with BCG and stimulated with either Mycobacterium tuberculosis or Staphylococcus aureus. We further assessed the impact of genetic variants in genes crucial for the biological activity of IFNγ pathway on trained immunity using single nucleotide polymorphism (SNP) genotyping. We found a significant correlation between baseline IFNγ production capacity and induction of trained immunity, as assessed by the fold-change increase in IL-6 production at both day 14 and day 90 post-vaccination compared to production before vaccination. A similar correlation was found between basal IFNγ production and increased IL-1β production at day 14 after BCG. This suggests that individuals with higher IFNγ production capacity exhibit stronger trained immunity responses post-BCG vaccination. This hypothesis is supported by the finding that SNPs in genes involved in the IFNγ biological pathway significantly influence trained immunity responses in humans. IFNγ production capacity and genetic variations in the IFNγ pathway genes impact the magnitude of trained immunity response, providing insights into the regulation of innate memory responses.
    Keywords:  BCG; Cytokine response; Genetic variation; Interferon-γ; Trained immunity
    DOI:  https://doi.org/10.1038/s41598-025-16350-5
  2. Elife. 2025 Oct 10. pii: e107552. [Epub ahead of print]14
      Innate immune cells possess memory-like properties. Exposure to infections or sterile inflammation can prime them, leading to either exacerbated inflammatory responses, a process called trained immunity, or reduced responsiveness to pro-inflammatory signals, a process termed immune tolerance. Microglia, the resident innate immune cells of the central nervous system, are central players in neurodegenerative diseases. Characterizing trained immunity and tolerance in microglia is necessary for a better understanding of neurodegenerative diseases. Cell metabolic processes orchestrate microglia inflammatory responses and promote epigenetic changes shaping immune memory in microglia. Here, we review current knowledge on the role of cell metabolic pathways in microglia innate immune memory formation, focusing on glucose, glutamine, and lipid metabolism. Moreover, we address the significance of microglial immune memory in disease pathology and discuss the potential of therapeutic targeting of cell metabolic pathways in neurodegenerative disorders.
    Keywords:  cell metabolism; immunology; inflammation; microglia; tolerance; training
    DOI:  https://doi.org/10.7554/eLife.107552
  3. Trends Immunol. 2025 Oct 06. pii: S1471-4906(25)00227-3. [Epub ahead of print]
      The evolution of the fetal immune system within the womb is a delicate balancing act: it is trained to not reject maternal antigens, while equipping itself with 'learned' immunity to survive and thrive in the outside world. In this opinion article, we propose that a deliberate maternal touch via immune and nutritional influences, orchestrated, in part, by microbiota-derived components, imprints the fetal immune system with the needed immune memory and epigenetic marks to navigate a far less nurturing outside world, including early microbial colonizers in the newborn's intestine, pathogens and irritants, and allergens in food. We redefine the hygiene hypothesis to include prenatal maternal microbial exposures, priming fetal immune development for long-term fitness and reduced inflammatory/autoimmune disease risk.
    Keywords:  immune imprinting; maternal–fetal immune tolerance; metabolite; microbiota
    DOI:  https://doi.org/10.1016/j.it.2025.09.008
  4. NPJ Metab Health Dis. 2024 May 27. 2(1): 6
      The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.
    DOI:  https://doi.org/10.1038/s44324-024-00008-3
  5. Cell Death Discov. 2025 Oct 07. 11(1): 449
      The shortage of liver donors for liver transplantation is currently an urgent problem. Elderly donors have become an important source of donor livers, but they are more prone to ischemia reperfusion injury (IRI) in liver transplantation. Therefore, exploring the effects and mechanisms of aging on liver IRI will provide a new theoretical basis for improving the survival rate of liver transplant patients. We constructed a mouse model of liver ischemia for 90 min and reperfusion for 6 or 24 h, and found that compared with young liver, the recovery of liver function in aged liver after IRI was slower. Detection of macrophage pyroptosis revealed that it was an important factor for aging deferring liver function restoration. Mechanistically, we demonstrated that aging triggered mitochondrial permeability transition pore (mPTP) channel opening to promote the release of Oxidized mtDNA (Ox-mtDNA), thereby inducing macrophage pyroptosis. Moreover, the activity of mPTP channel was mainly dependent on calcium uptake by acetylated mitochondrial calcium uniporter (MCU). These results illustrated that cytoplasmic Ox-mtDNA-induced macrophage pyroptosis was a key factor for aging exacerbating liver IRI. Calcium uptake via acetylated MCU triggered mPTP channel opening, which is an important mechanism for Ox-mtDNA release from mitochondria into the cytoplasm.
    DOI:  https://doi.org/10.1038/s41420-025-02746-9
  6. J Immunol. 2025 Oct 10. pii: vkaf272. [Epub ahead of print]
      Sepsis followed by multiple organ failure is a leading cause of death in noncoronary intensive care units. While the NLRC4 inflammasome has been shown to play a crucial role in the innate immune response, the role of NLRC4 in sepsis remains unclear. Here, we used NLRC4 gene-deficient mice to explore its role in cecal ligation and puncture (CLP)-induced polymicrobial sepsis. Survival, bacterial clearance in the lung and extrapulmonary organs, and leukocyte influx to the peritoneum were determined. Chemokines and cytokines in the peritoneal fluid (PF) were quantified using ELISA. Mice were co-housed to compare the gut microbiota's effect on bacterial burden following sepsis. Here, we report that NLRC4 deficiency improves host survival and bacterial clearance in mice with CLP-induced sepsis. Nlrc4-/- mice displayed reduced numbers of total leukocytes in the PF, including neutrophils compared to wild-type (WT) mice at 12 and 24 h post-CLP, although the recruitment of macrophages in NLRC4 knockout mice was higher at 12 h. Nlrc4-/- mice displayed lower levels of cytokines and chemokines in PF following sepsis. Co-housing of WT and Nlrc4-/- mice suggests that NLRC4 regulates host defense in CLP-induced sepsis independently of gut microbiota. Depletion of macrophages demonstrated that NLRC4 deficiency protects macrophages from sepsis-induced immune dysfunction. Moreover, we observed higher CD4+, CD8+, IFN-γ+CD8+, and NK cell subsets in the spleen and lower level of apoptosis of spleen cells of NLRC4-deficient mice after sepsis. Overall, these findings identify that NLRC4 activation has a detrimental role in sepsis through modulating macrophages and T-cell responses.
    Keywords:  Chemokine; Cytokine; NLRC4; Neutrophil; Sepsis
    DOI:  https://doi.org/10.1093/jimmun/vkaf272
  7. Eur J Immunol. 2025 Oct;55(10): e70068
      Severe COVID-19 is an immunological disorder characterized by a hyper-inflammatory reaction of the immune system. SARS-CoV-2 anti-spike antibodies of the IgG isotype are known to strongly contribute to this hyperinflammation by overactivation of alveolar macrophages. However, while the pathogenic function of IgG has been extensively studied, very little is known about the function of IgA, the most abundant immunoglobulin isotype in the airways. Although IgA is generally considered noninflammatory, in this study, we show that anti-spike IgA induces pronounced proinflammatory responses. We demonstrate that stimulation of macrophages with anti-spike IgA immune complexes in combination with a viral stimulus amplifies proinflammatory cytokine production. This IgA-induced inflammation is particularly driven by IgA2, the IgA subclass that is increased in the plasma of severely ill COVID-19 patients. We identified that IgA2-induced inflammation is predominantly dependent on FcαRI-Syk signaling. Mechanistically, IgA2-induced inflammation is linked to enhanced glycolysis and altered mitochondrial function, indicating subclass-specific immunometabolic reprogramming. Taken together, these data indicate a pathogenic role for IgA2 in severe COVID-19 and highlight its signaling cascades and metabolic pathways as potential druggable targets to counteract hyperinflammation in severe coronavirus infections, such as COVID-19, SARS, MERS, and potential future outbreaks.
    Keywords:  COVID‐19; IgA; immunometabolism; inflammation; macrophage
    DOI:  https://doi.org/10.1002/eji.70068