Developmental Immunology and Peripheral Tolerance

Full Citation:: Mohtashami M, Zúñiga-Pflücker JC. Immune tolerance and the prevention of autoimmune diseases essentially depend on thymic tissue homeostasis. Frontiers in Immunology. 2024;15:1339714. DOI:: 10.3389/fimmu.2024.1339714 PMID:: 38455041 PMCID:: PMC10918340 Published:: February 2024 Study Design:: Review article Key Findings::

- Immune tolerance and prevention of autoimmune disease fundamentally depend on continuous thymic tissue homeostasis and output of centrally tolerised naive T cells
- Thymic output is highest in childhood, with rigorous negative selection against self-antigens continuing through adolescence
- Thymic involution accelerates after puberty, reducing naive T cell output and diminishing the capacity to eliminate autoreactive clones via central tolerance
- Disrupted thymic homeostasis creates vulnerability for autoimmune disease by permitting escape of autoreactive clones into the periphery

Relevance to ME/CFS:: Supports the immune memory pruning hypothesis (Hypothesis Immune Memory Pruning in Development). Active thymic output during childhood and adolescence supplies naive, centrally tolerised T cells capable of suppressing autoreactive populations; adult thymic involution removes this regenerative capacity. Explains why paediatric immune systems may more effectively clear autoreactive clones generated during ME/CFS-triggering infections. Certainty Assessment::

- *Quality:* Medium-High (Frontiers in Immunology; Zúñiga-Pflücker is a leading T cell development researcher)
- *Study type:* Mechanistic review; thymic involution is a well-characterized phenomenon
- *Limitations:* Thymic output is relevant primarily for T cell tolerance; application to B cell-mediated GPCR autoantibody clearance requires additional inferential steps

Full Citation:: Meffre E, O’Connor KC. B cell tolerance and autoimmunity: Lessons from repertoires. Journal of Experimental Medicine. 2024;221(9):e20231314. DOI:: 10.1084/jem.20231314 PMID:: 39115642 Published:: September 2024 Study Design:: Review article Key Findings::

- B cell immune diversity, while enabling pathogen recognition, simultaneously creates risk of self-recognition leading to autoimmunity
- Autoreactive B cells not properly eliminated by negative selection can mature and differentiate into plasma cells producing pathological autoantibodies
- Disruption of negative selection barriers (central or peripheral) is a primary mechanism for autoimmune disease initiation
- Infection, inflammation, or developmental disruption can release autoreactive clones into antibody-producing niches where they become long-lived plasma cells resistant to elimination

Relevance to ME/CFS:: Directly supports the immune memory pruning hypothesis. Demonstrates that autoreactive B cells capable of producing GPCR or other autoantibodies can escape tolerance checkpoints when disrupted during viral infection. Explains variable rituximab benefit in ME/CFS: depletion without restoring tolerance mechanisms allows autoreactive reconstitution. Certainty Assessment::

- *Quality:* High (*Journal of Experimental Medicine*; Meffre and O'Connor are established B cell tolerance experts)
- *Study type:* Comprehensive mechanistic review
- *Limitations:* ME/CFS-specific B cell tolerance data are limited; application to GPCR autoantibody persistence is inferential

Full Citation:: Wirth KJ, Scheibenbogen C. Imbalance of Excitatory and Inhibitory Neurotransmitter Pathways in ME/CFS and Long COVID. Preprints.org (preprint, not peer-reviewed). 2025. URL:: https://www.preprints.org/frontend/manuscript/025f093892ed0dc2aef00d95d0f2fb85/download_pub Published:: 2025 Study Design:: Theoretical/mechanistic preprint (not peer-reviewed) Key Findings::

- Proposes systematic imbalance between excitatory and inhibitory neurotransmitter pathways in ME/CFS and Long COVID
- Examines dysregulation across acetylcholine, serotonin, GABA, and glutamate systems
- Autonomic dysfunction may result from cholinergic-adrenergic imbalance secondary to autoantibodies targeting muscarinic and adrenergic receptors
- Central sensitization and cognitive symptoms may reflect disturbed glutamate/GABA equilibrium

Relevance to ME/CFS:: Provides a mechanistic bridge between documented autoantibodies against adrenergic and muscarinic receptors and the full ME/CFS symptom spectrum. Relevant to the immune memory pruning hypothesis: autoantibody-mediated receptor dysfunction may persist even after viral clearance, causing ongoing neurotransmitter dysregulation. Certainty Assessment::

- *Quality:* Low-Medium (preprint; not peer-reviewed; treat as hypothesis-generating only)
- *Study type:* Theoretical synthesis; no new empirical data
- *Limitations:* Preprint; theoretical framework requires empirical validation; some prior Wirth/Scheibenbogen theoretical mechanisms have not been independently validated
- *Note:* Must be flagged as preprint in any citation context; not to be cited as established evidence