Biology subjects

Smolders, J.

Publications and source records attributed to Smolders, J..

6 recordsLinked to original sources

bioRxiv2025

Mapping Leukocyte Dynamics during Neuroinflammation Identifies Meningeal Monocyte-Derived Macrophages as Drivers of Progressive Disease

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by increasing disability. The cellular and molecular drivers of clinical transition towards progressive disease are poorly understood. Here, we combine single-cell profiling technologies with genetic and pharmacological perturbations across the course of murine CNS inflammation to dissect the role of the local immune landscape in disease progression. We uncover a chronic monocyte-to-phagocyte transition as a hallmark of progressive disease, characterized by the emergence of maladaptive, lipid-associated macrophages (LAMs) marked by lysosomal activation and fibrotic features. Spatial transcriptomics and multiplexed imaging revealed that these LAMs localized to the leptomeninges in close proximity to parenchymal colony-stimulating factor (CSF)-1 producing disease-associated microglia (DAMs) and meningeal granulocyte-macrophage (GM)-CSF-expressing T helper cells that license their differentiation. Interference with this local cytokine network revealed a protective role for resident microglia and implicated monocyte-derived phagocytes as key drivers of progressive neuroinflammation. Notably, LAM-like macrophages could also be identified in the meninges of people with MS, indicating a homology to human disease. By elucidating their ontogeny, spatial niche, and regulatory cytokine milieu, we provide a mechanistic framework for targeting harmful myeloid states while preserving reparative CNS immunity in progressive MS.

immunology↗

bioRxiv2025

Increased numbers of CD4+ T-cells in hypocretin/orexin region of Narcolepsy Type 1

Narcolepsy type 1 (NT1) is proposed to be an autoimmune disorder targeting hypothalamic hypocretin (orexin, Hcrt) neurons. Hcrt reactive T-cells have been identified in blood and cerebrospinal fluid (CSF) of NT1 patients. However, it remains unknown whether T-cells infiltrate the brain. Since T-cells can be retained for a lifetime in tissues as tissue resident memory T-cells after primary antigen exposure, we now systematically assess the presence of CD4+ and CD8+ T-cells in NT1 brains to determine their regional distribution and potential autoimmune involvement in NT1 neuropathology. We immunohistochemically stained and quantified CD4+ and CD8+ T-cells in post-mortem brain tissue of NT1 patients (n=5) and matched controls (n=5) in the Hcrt region, paraventricular nucleus (PVN) and median eminence (ME) as well as in the substantia nigra (SN) and locus coeruleus (LC). To phenotypically characterize CD4+ T-cells, we performed double staining with CD49a or C-X-C chemokine receptor type 6 (CXCR6). Furthermore, we stained for fibrinogen to estimate blood-brain barrier integrity, as well as microglia markers and an astrocyte marker to evaluate acute immune reactivity in the Hcrt region of NT1 brains. In NT1 there was an 11-fold increase in total number of CD4+ T-cells in the Hcrt region, but not in the PVN, ME, nor SN or LC. These CD4+ T-cells exhibited tissue residential memory features with double staining with CD49a or CXCR6. There were no changes in blood-brain barrier integrity, microglia and astrocyte staining intensities between NT1 and controls. In addition, the total number of CD4+ T-cells in the Hcrt region showed significant negative correlations with mean sleep latency in NT1 cases. Our findings suggest an enrichment of CD4+ T-cells specifically in the Hcrt region of NT1 indicating prior local antigen engagement. Moreover, greater CD4+ T-cell presence in the Hcrt region of NT1 was associated with increased symptom severity, as reflected by shorter sleep latency. These data support the hypothesis that CD4+ T-cells infiltrate the Hcrt region, where they may contribute to the autoimmune process that initiates NT1.

neuroscience↗

bioRxiv2025

Multiple sclerosis-associated HLA demarcates EBV-specific CD8+ T cells with an exhausted and brain residency phenotype

Specific HLA class I subtypes as well as circulating antibodies against Epstein-Barr virus (EBV) have been associated with increased susceptibility to develop multiple sclerosis (MS). It is currently unclear whether and how these risk factors are functionally related. Here, we assessed the impact of MS risk allele HLA-B7 and protective allele HLA-A2 on the effector phenotype of EBV-specific CD8+ T cells and if this corresponds with anti-EBV IgG titers. For this, we selected HLA-A2+ and/or HLA-B7+ donors with and without MS and analyzed HLA-restricted, EBV- specific CD8+ T cells with different fine-specificities using 38 color-based spectral flow cytometry. In contrast to HLA-A2-restricted CD8+ T cells, HLA-B7-restricted CD8+ T cells showed a confined response to EBV, which was mainly directed against latent peptide EBNA3A(379-387). These HLA-B7-restricted EBV-specific CD8+ T cells expressed higher levels of CNS residency markers CXCR3 and CD20 and were most abundant in fresh single-cell suspensions derived from different post-mortem CNS compartments of an HLA-A2+B7+ MS donor. Moreover, HLA-B7- restricted EBV-specific CD8+ T cells displayed a more exhausted phenotype (PD- 1+CD244+CD160+KLRG1+TIGIT+) that stood out in the blood from people with MS (pwMS). Accordingly, in the blood, increased IgG titers against EBV were found for pwMS carrying HLA- B7 but lacking HLA-A2, which seemed to coincide with HLA-B7-restricted EBV-specific CD8+ T cells having such an effector phenotype. These data support a model in which the confined response against EBV makes circulating HLA-B7-restricted CD8+ T cells less able to control EBV and more prone to infiltrate the CNS in pwMS.

immunology↗

bioRxiv2024

Microglial states determine lesion dynamics in multiple sclerosis

Summary paragraphMultiple sclerosis (MS) is a neuroinflammatory disease of the central nervous system, characterized by demyelinating lesions 1. Lesion expansion contributes to progression and increased disability, while remyelination can recover neurological deficits. However, mechanisms driving lesion dynamics are largely unclear, hindering the development of effective therapeutics. We propose that distinct states of microglia are involved in lesion expansion and remyelination 2,3. Using Stereo-seq, an RNA capture based high-resolution spatial transcriptomics technology with single-cell resolution, on post-mortem human brain tissue, we compared mixed active/inactive lesions with lipid-laden foamy microglia with lesions containing ramified microglia. We identified distinct cellular and molecular mechanisms underlying lesion activity and remyelination, linked to microglia phenotypes and states. Lesions with foamy microglia were characterized by elevated immune activation, increased lymphocyte densities, upregulated immunoglobulin production (IGHG1, IGHG3), increased complement system activity, indication of iron dysregulation (FTL, FTH1), and increased demyelination. In contrast, lesions with ramified microglia exhibited gene expression profiles indicative of myelin stability (ABCA2, QKI) and neuro-axonal protection, fostering an environment conducive to repair and remyelination. Our findings highlight the role of microglial states in lesion expansion and repair in MS and offer promising avenues for the development of therapeutic approaches aimed at preventing MS disability progression.

neuroscience↗

bioRxiv2024

CD4+ Trm sustain the chronic phase of auto-immune neuroinflammatory disease

Therapeutic options against multiple sclerosis (MS) preventing T cell migration to the central nervous system (CNS) have remarkable clinical effects against the relapsing-remitting (RRMS) form of the disease, while they are poorly effective against its progressive form (PMS). Disability progression in PMS is thought to result from an interplay between smoldering local inflammation and neurodegeneration. We postulated that an ongoing inflammatory process mediated by CNS-resident memory CD4+ T cells (CD4+ Trm) could contribute to promote disease chronicity independently of de novo recruitment of peripheral autoreactive T cells. Indeed, our results revealed the presence of bona fide CD4+ Trm expressing CD69, CXCR6, P2RX7, CD49a and the transcription factor Hobit in the CNS of mice with chronic experimental autoimmune encephalomyelitis (EAE) and in the brain of persons with PMS. Single-cell transcriptional analysis uncovered their transcriptional heterogeneity and inflammatory potential and, accordingly, CD4+ Trm preferentially localized within inflammatory lesions. Finally, depletion of both the recirculating and the CNS-resident CD4+ T cell compartments was required to alleviate neurological signs during the chronic phase of EAE. Our results, therefore, indicate that CD4+ Trm actively contribute to maintain a chronic inflammatory state in the CNS, promoting damage and/or preventing repair, and suggest that new therapeutic strategies for the treatment of PMS should consider targeting the CNS-resident T cell compartment.

immunology↗

bioRxiv2023

Profiling of microglia nodules in multiple sclerosis reveals propensity for lesion formation

Clusters of ramified HLA-DR+ cells, known as microglia nodules, are associated with brain pathology. Here we investigated if microglia nodules in the normal-appearing white matter (NAWM) of multiple sclerosis (MS) are different from microglia nodules in white matter (WM) in stroke and whether they may relate to the start of demyelinating MS lesions. We studied the relation between microglia nodules and pathological severity in an MS autopsy cohort (n=167), and we compared frequency, size, and gene expression of microglia nodules in MS (n=7) and stroke (n=7). MS donors with microglia nodules (64%) had a higher lesion load and a higher proportion of active lesions compared to donors without microglia nodules (36%). We found altered expression of genes in microglia nodules in MS compared to stroke, including genes previously shown to be upregulated in MS lesions. Genes associated with lipid metabolism, presence and proliferation of T and B cells, production of and response to immunoglobulins and cytokines (specifically TNF and IFN), activation of the complement cascade, and metabolic stress were upregulated. Using immunohistochemistry, we confirmed that in MS, more than in stroke, microglia nodules are associated with membrane attack complexes, have phagocytosed oxidized phospholipids, and have a tubular mitochondrial network reflecting increased metabolic activity. Furthermore, in MS, some nodules encapsulated partially demyelinated axons. Taken together, we propose that activation of some microglia nodules in MS by pro-inflammatory cytokines and immunoglobulins in combination with phagocytosis of oxidized phospholipids may lead to a volatile phenotype prone to form MS lesions.

neuroscience↗