Biology subjects

Fisher, T. M.

Publications and source records attributed to Fisher, T. M..

3 recordsLinked to original sources

bioRxiv2026

IFNγ and proinflammatory cytokines cooperatively license astrocytes to support antigen-dependent CD4+ T cell restimulation

We report that type 2 interferon with proinflammatory cytokines induces astrocytes to express multiple components required for attraction of and antigen presentation to CD4+ T cells via MHC-II molecules. Re-analysis of astrocyte-enriched single-cell sequencing from bacterial mimetic-injected mice revealed a transcriptionally distinct interferon-responsive astrocyte population enriched for antigen-presentation-associated genes 24 hours after peripheral immune challenge. In vivo, we identify MHC-II+GFAP+ astrocytes localized to the surface of the brain across multiple mouse models of neuroinflammation and in human neurological disease tissue. In a pure in vitro culture system, astrocytes stimulated with IFN{gamma} and proinflammatory cytokines express MHC-II, costimulatory molecules and lymphocyte-recruiting chemokines, and support rapid antigen-dependent expansion of previously activated CD4+ T cells. Using human iPSC-derived CNS cultures, we additionally show induction of antigen-presentation-associated machinery in human astrocytes following inflammatory cytokine stimulation. Rather than inferring function solely from marker expression, we assessed astrocyte-supported T cell restimulation in vitro and separately characterized the emergence of antigen-presentation-associated astrocytes in vivo at neuroimmune interfaces during inflammation in mice and humans. Together, these findings support a conserved role for cytokine-stimulated astrocytes in expressing antigen-presentation-associated machinery and, in vitro, supporting antigen-dependent restimulation/expansion of CD4+ T cells under inflammatory conditions.

neuroscience↗

bioRxiv2025

Early-life stromal niches orchestrate B lymphopoiesis at the brain's borders

The dura mater serves as a critical immunological niche for the central nervous system, yet the mechanisms governing the emergence of this niche in early life remain understudied. Here, we chart the trajectory of dural immune development, uncovering a distinctive function for the murine dura as a transient niche for B lymphopoiesis in the early-postnatal window. Shared embryonic progenitors initiate dural B cell development in concert with a multi-organ wave of extramedullary lymphopoiesis that contributes distinctively to the peripheral B cell pool. In the dura, B cells develop locally in discrete sinus-proximal foci, occupying an anatomically defined and developmentally restricted fibroblast niche. Sinus-proximal fibroblasts express the pro-hematopoietic chemokine CXCL12, and local deletion of this crucial factor severely impairs dural B lymphopoiesis. These data reveal a critical function for dural fibroblasts in shaping the early-life B cell compartment and provide a model for how extramedullary niches may support early-life leukocyte production.

immunology↗

bioRxiv2021

Vascular and perivascular cell profiling reveals the molecular and cellular bases of blood-brain barrier heterogeneity

SUMMARY The blood-brain barrier (BBB) is critical for protecting the brain and maintaining neuronal homeostasis. Although the BBB is a unique feature of the central nervous system (CNS) vasculature, not all brain regions have the same degree of impermeability. Differences in BBB permeability are important for controlling the local extracellular environment of specific brain regions to regulate the function and plasticity of particular neural circuits. However, how BBB heterogeneity occurs is poorly understood. Here, we demonstrate how regional specialization of the BBB is achieved. With unbiased cell profiling in small, defined brain regions, we compare the median eminence, which has a naturally leaky BBB, with the cortex, which has an impermeable BBB. We identify hundreds of molecular differences in endothelial cells (ECs) and demonstrate the existence of differences in perivascular astrocytes and pericytes in these regions, finding 3 previously unknown subtypes of astrocytes and several key differences in pericytes. By serial electron microscopy reconstruction and a novel, aqueous-based tissue clearing imaging method, we further reveal previously unknown anatomical specializations of these perivascular cells and their unique physical interactions with neighboring ECs. Finally, we identify ligand-receptor pairs between ECs and perivascular cells that may regulate regional BBB integrity in ECs. Using a bioinformatic approach we identified 26 and 26 ligand-receptor pairs underlying EC-pericyte and EC-astrocyte interactions, respectively. Our results demonstrate that differences in ECs, together with region-specific physical and molecular interactions with local perivascular cells, contribute to BBB functional heterogeneity. These regional cell inventories serve as a platform for further investigation of the dynamic and heterogeneous nature of the BBB in other brain regions. Identification of local BBB specializations provides insight into the function of different brain regions and will permit the development of region-specific drug delivery in the CNS.

neuroscience↗