Fibroblasts and immune cells coordinate tissue regeneration and necessary scarring after injury. In the brain, fibroblasts are border-enriched cells whose dynamic molecular states and immune interactions after injury remain unclear1. Here we define the shared fibroblast-immune response to brain injury. Early profibrotic myofibroblasts develop from pre-existing brain fibroblasts and infiltrate brain lesions, orchestrated by fibroblast TGFβ signalling, profibrotic macrophages and microglia, and perilesional glia. Myofibroblasts transition into several late fibroblast states, including lymphocyte-interactive fibroblasts. Interruption of the early myofibroblast state exacerbated sub-acute brain injury, tissue loss and secondary neuroinflammation, with increased mortality in the transient middle cerebral artery occlusion stroke model. Disruption of late lymphocyte-fibroblast niches via selective loss of fibroblast chemokine CXCL12 led to late brain-specific innate inflammation and lymphocyte dispersal with increased IFNγ production. These data indicate the response to brain injury is coordinated by evolving temporal and spatial fibroblast states that limit functional tissue loss and chronic neuroinflammation.
© 2025. The Author(s).

Cellular senescence in stem cells compromises regenerative capacity, promotes chronic inflammation, and is implicated in aging. Hematopoietic stem and progenitor cells (HSPCs) are responsible for producing mature blood cells, however, how cellular senescence influences their function is largely unknown. Here, we show that JMJD3, a histone demethylase, activates cellular senescence by upregulating p16Ink4a in competition with Polycomb group proteins, and reprograms HSPC integrity to overcome hematopoietic defects induced by replicative and oncogenic stresses. Jmjd3 deficiency does not alter global H3K27me3 levels, indicating that JMJD3 epigenetically regulates specific and limited JMJD3 targets under stress. JMJD3 deficiency also impairs stem cell potential, proper cell cycle regulation, and WNT pathway activation in HSPCs under stress. These impaired phenotypes are rescued through exogenous and retroviral introduction of p16Ink4a. This JMJD3-p16INK4a axis in hematopoiesis is age-dependent and is distinct from cellular senescence. Treatment with a selective JMJD3 inhibitor attenuates leukemic potential during cellular senescence. Taken together, these results demonstrate that JMJD3-p16INK4a mediates cellular senescence and plays critical roles in the functional integrity of HSPCs under stress.
© 2025. The Author(s).

Recent studies suggest that CD4+ T cells can exert potent anti-tumor effects and improve immunotherapy efficacy by aiding CD8+ T cells. However, characterizing the mechanism of CD4+ T cells' anti-tumor activity has been challenging due to inaccurate major histocompatibility complex class II (MHC-II) peptide prediction algorithms and the lack of high-quality reagents for immune monitoring. To address this, we developed MHC2-substitution of CLIP and analytical LCMS evaluation (MHC2-SCALE), a streamlined approach combining affinity optimized class II-associated invariant chain peptide (CLIP) exchange technology, high throughput 2D-LCMS analysis, and rapid generation of peptide-bound MHC-II monomers for subsequent multimer assembly. We validated MHC-II peptide candidates predicted by the immune epitope database (IEDB) algorithm, as well as uncovered many true and immunogenic MHC-II binders that were not predicted by IEDB. Thus, MHC2-SCALE expands the opportunities for discovering, tracking, and phenotyping antigen-specific CD4+ T cells in preclinical and clinical settings, thereby improving therapies for cancer, autoimmunity, or infectious diseases.
© 2025 The Author(s).

Cytotoxic lymphocytes are crucial to our immune system, primarily eliminating virus-infected or cancerous cells via perforin/granzyme killing. Perforin forms transmembrane pores in the plasma membrane, allowing granzymes to enter the target cell cytosol and trigger apoptosis. The prowess of cytotoxic lymphocytes to efficiently eradicate target cells has been widely harnessed in immunotherapies against haematological cancers. Despite efforts to achieve a similar outcome against solid tumours, the immunosuppressive and acidic tumour microenvironment poses a persistent obstacle. Using different types of effector cells, including therapeutically relevant anti-CD19 CAR T cells, we demonstrate that the acidic pH typically found in solid tumours hinders the efficacy of immune therapies by impeding perforin pore formation within the immunological synapse. A nanometre-scale study of purified recombinant perforin undergoing oligomerization reveals that pore formation is inhibited specifically by preventing the formation of a transmembrane β-barrel. The absence of perforin pore formation directly prevents target cell death. This finding uncovers a novel layer of immune effector inhibition that must be considered in the development of effective immunotherapies for solid tumours.
© 2025. The Author(s).

Public health alarm concerning the emerging fungus Candida auris is fueled by its antifungal drug resistance and propensity to cause deadly outbreaks. Persistent skin colonization drives transmission and lethal sepsis although its basis remains mysterious. We compared the skin colonization dynamics of C. auris with its relative C. albicans , quantifying skin fungal persistence and distribution and immune composition and positioning. C. auris displayed a higher propensity to colonize hair follicles and avidly bound to human hair. While C. albicans triggered an effective sterilizing type 3/17 antifungal immune response driven by IL-17A/F-producing lymphocytes, C. auris triggered a type 1, IFNγ-driven immune response targeting hair follicles. Rather than promoting fungal clearance, IFNγ enhanced C. auris skin colonization by acting directly on keratinocytes impairing epithelial barrier integrity and repressing antifungal defense programs. C. auris exploits focal skin immune responses to create a niche for persistence in hair follicles.