Aims: Conventional type 1 dendritic cells (cDC1) specialize in cross-presentation and interleukin-12 production and are critical for immunity against intracellular pathogens and tumors, but remain rare in vivo, limiting mechanistic and translational studies. Existing bone marrow-derived dendritic cell (BMDC) methods do not achieve selective enrichment of cDC1 or scalable production at high purity. We therefore aimed to establish a high-efficiency BMDC culture system for selective generation of CD103+ cDC1 from mouse bone marrow.

Methods: Mouse bone marrow cells were cultured in defined medium with recombinant FLT3L, low-dose GM-CSF, and Kit ligand (KitL) to generate induced cDC1 (iDC1). Phenotypic, transcriptomic, proteomic, phospho-proteomic, and functional analyses were performed and compared with established BMDC methods and ex vivo immune cell populations.

Results: iDC1 cultures enabled scalable generation of an estimated 1.5 × 10⁹ CD103⁺ cDC1 at greater than 95% purity from a single mouse, representing at least a 75-fold increase relative to previous recombinant cytokine-based methods. iDC1 closely aligned with the cDC1 lineage while distinct from macrophages. Functionally, iDC1 responded robustly to innate stimulation, secreted IL-12p40 and inflammatory chemokines, and efficiently cross-presented cell-associated antigen to CD8⁺ T cells. Mechanistically, KitL and GM-CSF cooperated during early cDC1 generation, whereas GM-CSF promoted proliferation and survival during later stages of culture. iDC1 generation depended on the +32 kb Irf8 enhancer, and STAT5- and BRD4-associated regulatory programs contributed to efficient iDC1 generation.

Conclusion: iDC1 cultures are a scalable platform for studying cDC1 biology and may facilitate development and preclinical evaluation of cDC1-based immunotherapeutic strategies.

Aims: Trained immunity, defined as long-term functional reprogramming of innate immune cells, has been implicated in the heterologous protective effects of certain vaccines against infection and cancer. AS01-adjuvanted vaccines have been suggested to provide such heterologous protective effects. We therefore aimed to investigate the capacity of AS01 to induce trained immunity and evaluated its potential as an antitumoral therapeutic.

Methods: Acute cytokine production was assessed in human monocytes after AS01 stimulation. Trained immunity was subsequently evaluated by IL-6 and TNF quantification following heterologous restimulation. Antitumor efficacy of AS01 was assessed in mice bearing B16-F10 melanoma, MB49 bladder cancer or Lewis lung carcinoma by monitoring tumor growth. Immune phenotyping of B16-F10 and MB49 tumor microenvironments was determined with flow cytometry.

Results: Although AS01 did not stimulate acute inflammation, it induced trained immunity, marked by increased responsiveness upon secondary stimulation in human monocytes. Treatment of mice bearing B16-F10 melanoma or MB49 bladder cancer with AS01 strongly diminished tumor growth, whereas no effect was observed in the Lewis lung carcinoma model. In these responsive models, the antitumor effects of AS01 were associated with an altered tumor microenvironment, characterized by increased infiltration of CD8⁺ T cells, regulatory T cells, neutrophils and monocytes, along with a decrease in tumor-associated macrophages. AS01 also decreased expression of immune checkpoint protein PD-L1 in monocytes and neutrophils, suggesting enhanced antitumor immune responsiveness.

Conclusion: Our findings show the capacity of AS01 to induce trained immunity and support its potential to be repurposed as an immunotherapeutic approach for cancer.

The autonomic nervous system (ANS) regulates myeloid cell biology across lymphoid and non-lymphoid tissues. Sympathetic, parasympathetic, and enteric circuits shape myeloid cell development, positioning or activation, and antigen presentation through norepinephrine, acetylcholine, dopamine and neuropeptides. In primary lymphoid organs, autonomic signals regulate myeloid progenitors and thymic macrophages, shaping the output and functional competence of innate immune compartments. In secondary lymphoid organs, most extensively characterized in the spleen, neural efferent pathways control macrophages, dendritic cells, monocytes and neutrophils, influencing phagocytosis, cytokine production and lymphocyte priming. Distinct neuro-myeloid interactions occur in the gut, where the enteric nervous system is a mandatory relay for parasympathetic signals to intestinal myeloid cells, and in the tumor microenvironment, where sympathetic and dopaminergic signals regulate tumor-associated myeloid subsets in tumor type-specific ways. The functional output of ANS-myeloid communication is guided by tissue context, myeloid cell identity, receptor type, and signal dynamics. The systemic characterization of these neuroimmune variables will be critical to design therapeutic strategies targeting the ANS-myeloid axis in infection, inflammation, autoimmunity and cancer.

Myeloid cells are central components of innate immunity and are highly responsive to environmental and lifestyle-associated cues. Among them, neutrophils are the most abundant circulating leukocytes in humans and have rapid turnover, traditionally leading to the view that they act mainly as short-lived effector cells. However, emerging evidence indicates that neutrophil function can be durably reshaped through upstream reprogramming of hematopoietic stem and progenitor cells and the bone marrow niche, resulting in trained-immunity-like changes in newly generated neutrophils. In this review, we discuss how lifestyle-associated factors shape neutrophil-associated immunity within the broader context of myeloid immune regulation, with a particular focus on long-term neutrophil functional reprogramming. We summarize current evidence that lifestyle and metabolic factors shape neutrophil production, mobilization, tissue recruitment, and effector programs. We further highlight that lifestyle induced neutrophil reprogramming is context dependent and may be either adaptive or maladaptive. Finally, we propose future directions for translating lifestyle-based immune modulation into strategies that limit chronic inflammation while preserving antimicrobial defense.

Parkinson’s disease (PD) is defined by the progressive accumulation of misfolded α-synuclein (αSyn) across the gut–brain axis, yet the cellular systems that normally contain this burden are only beginning to be understood. Among them, tissue-resident macrophages (RTM) occupy strategically positioned niches and functionally interact with their microenvironment. In this Perspective, we examine how muscularis externa macrophages in the enteric nervous system, parenchymal microglia, and border-associated macrophages in the central nervous system respond to αSyn and shape disease progression. We argue that these RTM serve as early sentinels of synucleinopathy by taking up extracellular αSyn and attempting to degrade it through lysosomal pathways. However, with ageing and in the context of genetic or environmental stress, this protective function may break down. As degradative capacity declines, RTM may enter dysfunctional states marked by cellular stress, incomplete processing of αSyn, propagation of pathogenic species, and enhanced antigen presentation. In this way, RTM may influence not only the local handling of αSyn, but also the emergence of adaptive immune responses and neuroinflammation across the enteric nervous system (ENS)–central nervous system (CNS) axis. We further discuss how anatomical niche, ontogeny, and αSyn conformational diversity may shape these responses, and how restoring macrophage proteostatic function could offer therapeutic opportunities to limit disease progression.

Multiple clinical and translational studies have shown that infiltration of tumour-associated neutrophils is associated with advanced disease stages, increased metastatic spread, therapeutic resistance, and poorer overall survival across various cancer types. Beyond their traditional role as first responders to tissue damage and pathogen infection, neutrophils within the tumour microenvironment (TME) display remarkable functional plasticity, adopting phenotypes that can promote angiogenesis, extracellular matrix remodelling, immune suppression, and tumour cell invasion. Importantly, it is now recognised that the prognostic impact of neutrophils is highly context-dependent, shaped by tumour type, stage, and the evolving inflammatory milieu. Intravital imaging studies have revealed dynamic neutrophil behaviours, including distinct migratory patterns between intra-tumoural and peri-tumoural regions, interactions with tumour and immune cells, and contributions to processes such as metastasis and immune suppression. However, there is a lack of understanding of how transcriptionally defined neutrophil subsets translate into specific functional and behavioural states in the TME in vivo. This mini-review spotlights intravital imaging approaches that illuminate neutrophil dynamics in tumours. We also discuss how extrinsic regulators, including cancer-associated fibroblasts and neural inputs, direct neutrophil dynamics, further contributing to TME complexity.

Macrophage efferocytosis is the phagocytic clearance of apoptotic cells. This fundamental process governs tissue homeostasis, immune tolerance, and the resolution of inflammation. Immune and metabolic reprogramming are essential to sustain efferocytic capacity. Maladaptive efferocytosis is mostly considered “incomplete or nonfunctional” in chronic diseases, but can also be characterized by misinterpreted, mistimed, or mischaracterized efferocytic events. A central barrier to progress has been the inability to define efferocytic macrophages as functional entities, rather than transient, poorly resolved states obscured by technical and conceptual limitations. Here, we review efferocytosis across health and disease by linking apoptotic cargo identity, macrophage processing capacity, and inflammatory and metabolic constraints to efferocytic throughput. We further highlight the technical challenges that cause the bona fide efferocytic states to be misclassified or excluded in high‑dimensional datasets. Applying an updated framework acknowledging the complexity of macrophage efferocytosis will ultimately enable the development of novel therapeutic strategies.

Aims: Conventional two-dimensional (2D) culture systems fail to recapitulate the structural and functional complexity of the brain parenchyma, driving microglia toward an activated, non-homeostatic state. Here, we therefore developed a simple, robust, and scalable three-dimensional (3D) culture system using a Matrigel-collagen composite matrix to promote a more in vivo-like microglial phenotype.

Methods: Primary mouse microglia and human induced pluripotent stem cell-derived microglia (iMGLs) from multiple donor lines were cultured either in conventional 2D conditions or embedded in a Matrigel-collagen 3D matrix. Phenotypes were characterized using confocal microscopy and morphometric analysis, live-cell imaging, transcriptomic profiling, electrophysiology, cytokine secretion assays upon inflammatory stimulation, and flow cytometry.

Results: In 3D culture, mouse microglia developed a markedly more ramified and structurally complex morphology, supported by filamentous actin-rich terminal processes. Live-cell imaging demonstrated enhanced dynamics of cell processes and a more sessile cell body, consistent with physiological microglia surveillance behavior. Transcriptomic profiling further revealed that microglia cultured in 3D downregulated genes associated with activation and proliferation while upregulating homeostatic markers, yet retained a robust cytokine response to inflammatory stimulation. Electrophysiological profiling similarly indicated a shift toward a more resting, in vivo-like state. Human iMGLs showed comparable morphological adaptations in 3D, with protein expression and functional readouts reflecting both shared homeostatic features and cell line- and context-dependent characteristics.

Conclusion: Together, our results demonstrate that a simple and accessible 3D culture system shapes microglial morphology, behavior, and molecular identity, establishing a versatile platform for investigating microglial physiology in a controlled yet physiologically more relevant environment.

Monocytes consist of several subsets, which differ in their phenotype and functional capacity. This heterogeneity was first shown in man, and later evidenced in other species. Here, we review the current knowledge on the phenotype and functionality of monocyte populations in species of veterinary interest, in comparison to man. The increasing availability of reagents for leukocyte phenotypic analyses, along with the growing application of -omic technologies, are enabling a better characterization of these subsets, and facilitating comparisons across species. The review demonstrates that classical, intermediate, and non-classical monocytes can be defined in pig, cattle, sheep, camel, buffalo, horse, and dog. However, more phenotypic, functional and transcriptomic studies are needed in some species to establish an accurate correspondence. A better understanding of shared and species-specific features of these monocyte subsets will pave the way for translational research on strategies selectively targeting these cells to treat different pathological conditions, including infectious, inflammatory and malignant diseases.

Myeloid cells play key roles in innate and adaptive immunity. Studying their development and function helps reveal new roles and pathogenic mechanisms of related diseases. Zebrafish, a classical model organism, offers various advantages for studying myeloid cell biology. In this review, we focus on recent advances in myeloid cell development and function using the zebrafish model. The pattern and regulation of myelopoiesis and related disorders, including congenital myeloid cell insufficiency and myeloid malignancies, have been revealed, along with related drugs. Regarding function, we highlight myeloid cells, especially macrophages, in homeostasis and regeneration. The bidirectional interactions between myeloid cells and pathogens in zebrafish also provide valuable insights into the mechanisms of infectious diseases. In summary, we highlight the unique contributions of the zebrafish model, demonstrate its complementary roles in basic research and clinical applications relative to mammalian systems, and look forward to more exciting discoveries using this model in the future.

Eosinophilic esophagitis (EoE) is a chronic, food antigen-driven, type 2 immune-mediated disease of the esophagus characterized by eosinophil-predominant mucosal inflammation, epithelial remodeling, and subepithelial fibrosis. Although patient biopsies have established the EoE transcriptome and identified key cellular and molecular mediators, biopsy-based research is inherently correlative and cannot resolve causal disease mechanisms, temporal disease progression or the functional hierarchy of immune cell interactions. Thus, animal models are indispensable tools for addressing these limitations. In this Review, we examine the landscape of experimental EoE models. We assess the capacity of each model to recapitulate key disease features including lamina propria and intraepithelial eosinophilia, subepithelial fibrosis, basal cell hyperplasia, epithelial barrier dysfunction, and angiogenesis. We further map these models to human EoE transcriptomic overlap and disease endotype relevance. Across this analysis, we highlight mechanistic insights that were obtained from these models including the eosinophil-independence of IL-13-driven esophageal remodeling, the respective roles of thymic stromal lymphopoietin and IL-33, and the critical role of epithelial-expressed IL-13Rα1. We further highlight the profibrotic functions of amphiregulin-producing T helper 2 cells and colony-stimulating factor 1-dependent macrophages. We discuss the anatomical, genetic and functional limitations of current models and outline directions for the next generation of EoE preclinical systems.