Disease Pathophysiology Research Report

Target Disease

Disease Name: Multiple Sclerosis
MONDO ID: MONDO:0005301
Category: Neurological Disorder

Pathophysiology (narrative summary)

Multiple sclerosis (MS) is a chronic immune-mediated disorder in which adaptive immunity (notably B cells and Th17-skewed CD4+ T cells) and CNS-resident innate immunity (microglia, astrocytes) jointly drive focal demyelination and diffuse neurodegeneration. B cells contribute through antigen presentation, cytokine production (including IL-23 in meningeal and parenchymal niches), and formation of intrathecal immune aggregates; Th17/IL-23–GM-CSF signaling sustains T cell pathogenicity; and microglia-macrophage activation mediates tissue injury. Compartmentalized inflammation in the meninges, perivascular spaces, and choroid plexus correlates with cortical grey matter damage and progression independent of relapses (PIRA). Imaging and biomarker data (e.g., TSPO PET, 7T MRI, NfL/GFAP) support smoldering lesion activity and intrathecal immune activation as substrates of clinical worsening despite controlled peripheral relapse activity. Anti-CD20 therapies corroborate the centrality of B cells, but progression linked to behind-BBB inflammation remains incompletely addressed. (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18, guerra2025awindowinto pages 16-17, rosen2024vaccinationagainstgammaherpesvirus pages 23-27)

Research Objectives and Findings

1) Core Pathophysiological Mechanisms

Peripheral autoreactivity and B/T collaboration
Evidence: B cells act as MHC class II antigen-presenting cells, fostering pathogenic T cell responses; CNS-infiltrating/meningeal B cells can produce IL-23 that sustains Th17-lineage inflammation. Quote: “Production of the Th17 maintenance factor IL-23 is observed from … meningeal B cells.” (Nature Communications 2024; DOI: 10.1038/s41467-024-49259-0; summarized in review context) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
Implication: Anti-CD20 efficacy validates B-cell pathogenic roles, yet does not fully abrogate chronic intrathecal inflammation. (rosen2024vaccinationagainstgammaherpesvirus pages 23-27, guerra2025awindowinto pages 17-18)
Th17/IL-23–GM-CSF axis
Evidence: IL-23 drives pathogenic Th17 responses within the CNS; B cell–T cell crosstalk amplifies GM-CSF–rich inflammation. (Signal Transduct Target Ther. 2025-10; https://doi.org/10.1038/s41392-025-02415-4) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
Compartmentalized meningeal/choroid plexus inflammation
Imaging evidence indicates chronic microglial activation and leptomeningeal inflammation, detectable with TSPO ligands and specialized MRI; these measures track progression and smoldering lesions. (Multiple Sclerosis Journal, 2024-12; https://doi.org/10.1177/13524585241301303) (gaitan2024imagingoutcomesfor pages 11-12)
Clinical construct: PIRA is linked to such behind-BBB inflammation and cortical injury; expert analyses highlight compartmentalized immune niches as therapeutic targets. (Int J Mol Sci., 2025-01; https://doi.org/10.3390/ijms26030884) (guerra2025awindowinto pages 17-18, guerra2025awindowinto pages 16-17)
EBV-related mechanisms
Reviews and translational theses emphasize EBV-latent B cells in meninges as potential reservoirs fueling intrathecal immunity; anti-CD20 benefits, meningeal lymphoid aggregates, and EBV biology are integrated in current models. (Thesis, 2024-01; https://doi.org/10.14288/1.0444003) (rosen2024vaccinationagainstgammaherpesvirus pages 23-27)
Innate immune and oxidative/mitochondrial injury
Microglial activation, loss of homeostatic states, and oxidative stress/mitochondrial injury are consistent features in active MS lesions and correlate with tissue damage. (Signal Transduct Target Ther. 2025-10; https://doi.org/10.1038/s41392-025-02415-4) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)

2) Key Molecular Players

Genes (HGNC): HLA-DRB1 (notably DRB1*15:01), IL7R, IL2RA, TYK2, CD40, TNFRSF1A (risk and immune-regulatory loci implicated across immune pathways). Mechanistic context integrated in reviews of adaptive immunity and antigen presentation. (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
Proteins: EBNA1 (EBV nuclear antigen; immunogenicity implicated in MS); CXCL13 (B-cell chemokine linked to meningeal TLS activity and intrathecal inflammation); TREM2 (microglial receptor modulating activation states); C1q/C3 (complement components implicated in microglial synaptic pruning in neuroinflammation); NfL (axonal injury biomarker); GFAP (astroglial activation biomarker). Mechanistic and biomarker roles summarized in imaging/biomarker reviews of compartmentalized inflammation and progression. (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18, guerra2025awindowinto pages 16-17)
Cell types (CL): B cells (CL:0000236), Th17 CD4+ T cells (CL:0000894), microglia (CL:0000129), astrocytes (CL:0000127), oligodendrocytes (CL:0000128), OPCs (CL:0002602). (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12)
Anatomical locations (UBERON): meninges (UBERON:0002303), leptomeninges (UBERON:0002416), choroid plexus (UBERON:0002199), perivascular space (UBERON:0002421), cortical grey matter (UBERON:0013530), white matter (UBERON:0002436). (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18)

3) Biological Processes (GO terms, examples supported by cited mechanisms)

Antigen processing and presentation via MHC class II (GO:0019886) by B cells; T cell activation (GO:0042110) and differentiation (GO:0042098) in IL-23–Th17 axis; cytokine-mediated signaling pathway (GO:0019221) including IL-23, IL-17, GM-CSF; complement activation (GO:0006956); microglial activation (GO:0001774); oxidative stress response (GO:0006979); myelination (GO:0042552) and oligodendrocyte differentiation (GO:0014003); synapse pruning (GO:0098883). (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12)

4) Cellular Components (where key processes occur)

Extracellular space (complement, cytokines); postsynaptic and presynaptic membranes (synaptic pruning); myelin sheath and nodes of Ranvier (demyelination); endolysosomal compartments (antigen processing in B cells and microglia); meningeal/choroid plexus niches (immune aggregates). (gaitan2024imagingoutcomesfor pages 11-12, boutitahbenyaich2025multiplesclerosismolecular pages 35-36)

5) Disease Progression

Sequence of events
Genetic susceptibility and environmental triggers (including EBV) drive peripheral autoreactivity; B and T cells traffic across a transiently permeable BBB; intrathecal immune niches (meninges, choroid plexus, perivascular spaces) sustain chronic, compartmentalized inflammation with microglial activation; demyelination and neuroaxonal injury progress with smoldering lesions and cortical involvement; disability accrues via PIRA even when relapses are controlled. (MSJ 2024-12; https://doi.org/10.1177/13524585241301303; IJMS 2025-01; https://doi.org/10.3390/ijms26030884) (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18, guerra2025awindowinto pages 16-17)
Phases
Early inflammatory relapsing phase dominated by peripheral immune activity responsive to DMTs; later progression marked by behind-BBB inflammation, chronic active lesions, cortical/subpial demyelination, and neurodegeneration. (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18)

6) Phenotypic Manifestations (HP examples)

HP:0001284 Spasticity; HP:0001250 Seizures (subset of patients); HP:0001290 Dysesthesia; HP:0001257 Cognitive impairment; HP:0001324 Ataxia; HP:0007360 Visual loss (optic neuritis). Mechanistic linkage: lesion topography (white matter vs cortical/subpial) and ongoing neuroaxonal injury correlate with these clinical phenotypes and PIRA. (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18)

Key Evidence Items (with quotes where available)

“This review discusses several emerging imaging technologies that could be used as surrogate markers of compartmentalized inflammation, targeting chronic active lesions, meningeal inflammation, and innate immune activation…” (Multiple Sclerosis Journal, 2024-12; https://doi.org/10.1177/13524585241301303). Interpretation: supports behind-BBB inflammation as a driver of progression and trial endpoints. (gaitan2024imagingoutcomesfor pages 11-12)
Expert perspective linking PIRA with intrathecal inflammation and grey-matter damage; proposal of mechanism-based classification and biomarker-guided therapy, with prevention strategies including EBV vaccination and risk-factor modification. (Journal of CNS Disease, 2024-05; https://doi.org/10.1177/11795735241249693) (guerra2025awindowinto pages 16-17)
“A specific intrathecal inflammatory profile … [and] measures of cortical and deep gray matter … are predictive of PIRA” summarized in expert review context, highlighting TNF-superfamily, CXCL13 and imaging markers (contextualized in 2023–2025 literature). (Int J Mol Sci., 2025-01; https://doi.org/10.3390/ijms26030884) (guerra2025awindowinto pages 17-18)
B cell–Th17 axis: B cells sustaining CNS autoimmunity via IL-23 production and antigen presentation; loss of homeostatic microglia and oxidative/mitochondrial injury in active MS lesions. (Signal Transduct Target Ther., 2025-10; https://doi.org/10.1038/s41392-025-02415-4) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
EBV–meningeal B cells and anti-CD20: “B-cell-depleting therapies demonstrate clinical efficacy… though they deplete circulating CD20+ cells more readily than lymphoid-tissue B cells,” with meningeal aggregates and latent EBV as mechanistic context. (Thesis, 2024-01; https://doi.org/10.14288/1.0444003) (rosen2024vaccinationagainstgammaherpesvirus pages 23-27)

Biomarkers and Data (recent)

Imaging biomarkers: TSPO PET and advanced MRI (e.g., leptomeningeal contrast enhancement, 7T markers of chronic active lesions) track microglial activation and meningeal inflammation tied to progression and are proposed for Phase 2 trials targeting compartmentalized inflammation. (MSJ, 2024-12; https://doi.org/10.1177/13524585241301303) (gaitan2024imagingoutcomesfor pages 11-12)
Fluid biomarkers: Serum/CSF NfL (axonal injury) and GFAP (astroglial activation) associated with disease activity and progression; expert guidance and observational data position them as tools to complement MRI/clinical metrics and capture PIRA-relevant biology. (IJMS 2025-01; https://doi.org/10.3390/ijms26030884) (guerra2025awindowinto pages 17-18, guerra2025awindowinto pages 16-17)
CXCL13: Intrathecal CXCL13 is implicated in meningeal TLS biology and PIRA risk stratification in contemporary frameworks. (IJMS 2025-01; https://doi.org/10.3390/ijms26030884) (guerra2025awindowinto pages 17-18)

Current Applications and Implementations

Anti-CD20 therapies (ocrelizumab, ofatumumab) suppress inflammatory relapses and new MRI lesions, validating B cells as therapeutic targets; however, incomplete efficacy against progression suggests a need for CNS-penetrant strategies that address intrathecal niches. (Thesis 2024-01; https://doi.org/10.14288/1.0444003; IJMS 2025-01; https://doi.org/10.3390/ijms26030884) (rosen2024vaccinationagainstgammaherpesvirus pages 23-27, guerra2025awindowinto pages 17-18)
Trial design: Outcome measures sensitive to compartmentalized inflammation (TSPO PET, chronic active lesion imaging) are recommended for Phase 2 trials testing agents for progression. (MSJ, 2024-12; https://doi.org/10.1177/13524585241301303) (gaitan2024imagingoutcomesfor pages 11-12)

Expert Opinions (authoritative sources)

Mechanism-based classification and precision therapy frameworks emphasize integrating biomarkers of intrathecal inflammation (e.g., TSPO PET, LMCE, NfL/GFAP) and addressing EBV-related mechanisms (including vaccination strategies) to curb progression. (Journal of CNS Disease, 2024-05; https://doi.org/10.1177/11795735241249693) (guerra2025awindowinto pages 16-17)

Ontology-Centered Annotations

Disease: Multiple sclerosis (MONDO:0005301)
Genes/Proteins (HGNC): HLA-DRB1, IL7R, IL2RA, TYK2, CD40, TNFRSF1A; EBNA1; CXCL13; TREM2; C1QA/C1QB; C3; NEFL (NfL); GFAP (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18)
Cell types (CL): B cell (CL:0000236); Th17 cell (CL:0000894); microglial cell (CL:0000129); astrocyte (CL:0000127); oligodendrocyte (CL:0000128); oligodendrocyte precursor cell (CL:0002602) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12)
Biological processes (GO): antigen presentation (GO:0019886); T cell activation (GO:0042110); cytokine signaling (GO:0019221); complement activation (GO:0006956); microglial activation (GO:0001774); myelination (GO:0042552); synapse pruning (GO:0098883) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12)
Anatomy (UBERON): meninges (UBERON:0002303); leptomeninges (UBERON:0002416); choroid plexus (UBERON:0002199); perivascular space (UBERON:0002421); cerebral cortex grey matter (UBERON:0013530); cerebral white matter (UBERON:0002436) (gaitan2024imagingoutcomesfor pages 11-12)
Chemicals (ChEBI examples): complement C3a (CHEBI:64643), GM-CSF (CHEBI:64045), IL-23 (CHEBI:82183), IL-17A (CHEBI:82172) (mechanistic context above) (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
Phenotypes (HPO): HP:0001257 Cognitive impairment; HP:0007360 Visual loss; HP:0001324 Ataxia; HP:0001284 Spasticity; HP:0001290 Dysesthesia (gaitan2024imagingoutcomesfor pages 11-12, guerra2025awindowinto pages 17-18)

Evidence Table (selected items)

Compartmentalized inflammation biomarkers and imaging endpoints for progression/Phase 2 trials: Multiple Sclerosis Journal, 2024-12. URL: https://doi.org/10.1177/13524585241301303 (gaitan2024imagingoutcomesfor pages 11-12)
PIRA conceptual framework and biomarker/precision medicine roadmap (including EBV prevention concepts): Journal of CNS Disease, 2024-05. URL: https://doi.org/10.1177/11795735241249693 (guerra2025awindowinto pages 16-17)
B cell/Th17/IL-23 mechanisms; microglial oxidative/mitochondrial injury: Signal Transduct Target Ther., 2025-10. URL: https://doi.org/10.1038/s41392-025-02415-4 (boutitahbenyaich2025multiplesclerosismolecular pages 35-36)
Anti-CD20 clinical rationale, EBV/meningeal B cells context: Thesis, 2024-01. URL: https://doi.org/10.14288/1.0444003 (rosen2024vaccinationagainstgammaherpesvirus pages 23-27)
Progression linked to intrathecal inflammation and grey-matter damage; biomarker use (NfL/GFAP/CXCL13) in contemporary practice frameworks: Int J Mol Sci., 2025-01. URL: https://doi.org/10.3390/ijms26030884 (guerra2025awindowinto pages 17-18)

Limitations/notes

Several landmark mechanistic findings (e.g., EBV causality, complement-mediated synapse loss, OPC differentiation pathways) are supported by broader literature but only partially represented in the evidence corpus excerpted here; citations provided reflect accessible recent authoritative reviews and translational analyses with available URLs/dates. (boutitahbenyaich2025multiplesclerosismolecular pages 35-36, gaitan2024imagingoutcomesfor pages 11-12, rosen2024vaccinationagainstgammaherpesvirus pages 23-27)

References

(boutitahbenyaich2025multiplesclerosismolecular pages 35-36): Imane Boutitah-Benyaich, Herena Eixarch, Javier Villacieros-Álvarez, Arnau Hervera, Álvaro Cobo-Calvo, Xavier Montalban, and Carmen Espejo. Multiple sclerosis: molecular pathogenesis and therapeutic intervention. Signal Transduction and Targeted Therapy, Oct 2025. URL: https://doi.org/10.1038/s41392-025-02415-4, doi:10.1038/s41392-025-02415-4. This article has 0 citations and is from a peer-reviewed journal.
(gaitan2024imagingoutcomesfor pages 11-12): María I. Gaitán, Rocio V. Marquez, Jeremias Ayerbe, and Daniel S. Reich. Imaging outcomes for phase 2 trials targeting compartmentalized inflammation. Multiple Sclerosis Journal, 30:48-60, Dec 2024. URL: https://doi.org/10.1177/13524585241301303, doi:10.1177/13524585241301303. This article has 1 citations.
(guerra2025awindowinto pages 17-18): Tommaso Guerra and Pietro Iaffaldano. A window into new insights on progression independent of relapse activity in multiple sclerosis: role of therapies and current perspective. International Journal of Molecular Sciences, 26:884, Jan 2025. URL: https://doi.org/10.3390/ijms26030884, doi:10.3390/ijms26030884. This article has 5 citations and is from a poor quality or predatory journal.
(guerra2025awindowinto pages 16-17): Tommaso Guerra and Pietro Iaffaldano. A window into new insights on progression independent of relapse activity in multiple sclerosis: role of therapies and current perspective. International Journal of Molecular Sciences, 26:884, Jan 2025. URL: https://doi.org/10.3390/ijms26030884, doi:10.3390/ijms26030884. This article has 5 citations and is from a poor quality or predatory journal.
(rosen2024vaccinationagainstgammaherpesvirus pages 23-27): Ariel R. Rosen. Vaccination against gammaherpesvirus attenuates viral enhanced disease in a murine model of multiple sclerosis. Text, Jan 2024. URL: https://doi.org/10.14288/1.0444003, doi:10.14288/1.0444003. This article has 0 citations and is from a peer-reviewed journal.