Biology subjects

Arnold, T. D.

Publications and source records attributed to Arnold, T. D..

6 recordsLinked to original sources

bioRxiv2026

AEGIS reveals epitope- and clone-resolved convergence of CNS B and T cell autoreactivity in ROHHAD

Autoimmune diseases arise when B and T lymphocytes lose tolerance to self. Yet in most disorders, the underlying molecular determinants, including autoantibodies, epitopes and lymphocyte clones that drive tissue injury remain undefined. Rapid-onset obesity with hypothalamic dysfunction, hypoventilation and autonomic dysregulation (ROHHAD) is a rare and often fatal pediatric neuroendocrine syndrome with strong evidence of antigen-driven paraneoplastic autoimmunity, including association with the intracellular autoantigen ZSCAN1. However, the effector immune circuit and the epitope-level determinants operating within the hypothalamus and brainstem have remained unknown. To address this challenge in ROHHAD and more broadly in autoimmune disease, we developed the Autoimmune Epitope and immunoGlobulin/Immune-receptor identification System (AEGIS), an integrated framework that links immune repertoires to their cognate self-epitopes. AEGIS combines B cell and T cell receptor profiling from sites of tissue injury with high-resolution epitope mapping, direct sequencing of antigen-specific autoantibodies, in silico antibody-antigen folding, selection, and T cell antigen discovery. Applied to a deeply phenotyped child with ROHHAD, AEGIS revealed a compartmentalized, clonally restricted immune response in which brain-deposited IgG and expanded cerebrospinal fluid B cell and CD4 T cell clonotypes converged on shared ZSCAN1 epitopes, resolved to minimal determinants and peptide-MHC ligands. These findings provide a clone- and epitope-linked mechanistic map of ROHHAD autoimmunity and establish a generalizable framework for identifying candidate pathogenic clones and antigens across diverse autoimmune diseases.

immunology↗

bioRxiv2024

Dynamic fibroblast-immune interactions shape wound healing after brain injury

Fibroblasts coordinate the response to tissue injury, directing organ regeneration versus scarring. In the central nervous system (CNS), fibroblasts are uncommon cells enriched at tissue borders, and their molecular, cellular, and functional interactions after brain injury are poorly understood. Here we define the fibroblast response to sterile brain damage across time and space. Early pro-fibrotic myofibroblasts infiltrated CNS lesions and were functionally and spatially organized by fibroblast TGF{beta} signaling, pro-fibrotic macrophages and microglia, and perilesional brain glia that activated TGF{beta} via integrin v{beta}8. Early myofibroblasts subsequently transitioned into a variety of late states, including meningeal and lymphocyte-interactive fibroblasts that persisted long term. Interruption of this dynamic fibroblast-macrophage-glial coordination impaired brain wound healing and the resolution of neuroinflammation, disrupted generation of late de novo CNS lymphocyte niches, and increased mortality in a stroke model. This work highlights an unexpected role of fibroblasts as coordinate regulators of CNS healing and neuroinflammation after brain injury.

immunology↗

bioRxiv2024

Microglia are not required for maintenance of blood-brain barrier properties in health, but PLX5622 alters brain endothelial cholesterol metabolism

Microglia are resident immune cells of the central nervous system, yet their functions far exceed those related to immunology. From pruning neural synapses during development to preventing excessive neural activity throughout life, microglia are intimately involved in the brains most basic processes. Studies have reported a close interaction between microglia and endothelial cells, as well as both helpful and harmful roles for microglia at the blood-brain barrier (BBB) in the context of disease. However, much less work has been done to understand microglia-endothelial cell interactions in the healthy brain. Here, we aim to determine the role of microglia at the healthy BBB. We used the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 to deplete microglia and analyzed BBB ultrastructure, permeability, and transcriptome. Interestingly, we found that, despite their direct contact with endothelial cells, microglia are not necessary for maintenance of BBB structure, function, or gene expression in the healthy brain. However, we found that PLX5622 treatment alters brain endothelial cholesterol metabolism, and this effect was independent from microglial depletion, suggesting PLX5622 has off-target effects on brain vasculature.

neuroscience↗

bioRxiv2023

Radial glia control microglial differentiation via integrin avb8-dependent trans-activation of TGFB1

Microglia diversity emerges from interactions between intrinsic genetic programs and environment-derived signals, but how these processes unfold and interact in the developing brain remains unclear. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) expressed in radial glia progenitors activates microglia-expressed TGF{beta}1, permitting microglial development. Domain-restricted deletion of Itgb8 in these progenitors establishes complementary regions with developmentally arrested "dysmature" microglia that persist into adulthood. In the absence of autocrine TGF{beta}1 signaling, we find that microglia adopt a similar dysmature phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the TGF{beta} signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Finally, we show that non-canonical (Smad-independent) signaling partially suppresses disease and development associated gene expression, providing compelling evidence for the adoption of microglial developmental signaling pathways in the context of injury or disease.

immunology↗

bioRxiv2020

Pericyte-specific vascular expression of SARS-CoV-2 receptor ACE2 - implications for microvascular inflammation and hypercoagulopathy in COVID-19 patients

Accumulating clinical observations implicate vascular inflammation as an underlying cause of coagulopathy in severely ill COVID-19 patients and it was recently suggested that SARS-CoV-2 virus particles infect endothelial cells. Here, we show that endothelial cells do not express angiotensin-converting enzyme-2 (ACE2), the SARS-CoV-2 receptor. Instead, pericytes and microvascular smooth muscle cells express ACE2 in an organotypic manner. Pericyte deficiency leads to increased endothelial expression and release of Von Willebrand factor and intravascular platelet and fibrin aggregation, suggesting that pericytes limit endothelial pro-thrombotic responses. That pericytes and not endothelial cells express ACE2 may provide important clues to the pathology of COVID-19, as pericytes are normally shielded behind an endothelial barrier and may get infected only when this barrier is compromised by COVID-19 risk factors.

pathology↗

bioRxiv2019

New Tools for Genetically Targeting Myeloid Populations in the Central Nervous System

As the resident macrophages of the brain and spinal cord, microglia are crucial for the phagocytosis of infectious agents, apoptotic cells and synapses. Developmentally, microglia originate from the embryonic yolk sac and serve important roles in the sculpting of neonatal neural circuits. During brain injury or infection, bone-marrow derived macrophages invade neural tissue, making it difficult to distinguish between invading macrophages and resident microglia. In addition to circulation-derived monocytes, other non-microglial central nervous system (CNS) macrophage subtypes include borderzone (meningeal and perivascular) and choroid plexus macrophages. To distinguish between resident microglia and these other CNS macrophage subtypes, we generated a P2ry12-CreER mouse line. P2RY12 is a microglial-specific nucleotide sensing GPCR that is important for microglial response to tissue damage. Using immunofluorescent labeling and flow cytometry experiments, we show that P2ry12-CreER recombination is exceptionally specific to parenchymal microglia. We also perform ribosome immunoprecipitations and transcriptional profiling of P2ry12-CreER recombined cells, using a Cre-dependent Rpl22-HA mouse line. By identifying genes enriched in this dataset that are not correspondingly enriched in a broader Cx3CR1-CreER; Rpl22 dataset, we isolate a number of borderzone macrophage-specific transcripts, including the gene PF4. Using a PF4-Cre mouse line, we show that PF4 expression robustly marks borderzone macrophages. Together, we demonstrate two new methods to genetically target distinct CNS macrophage subtypes.

immunology↗