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.