GPCR Autoantibody Cross-Disease Bridges
Certainty: 0.55. Fibromyalgia IgG passive transfer (Goebel/Mignolet/Chen 2021–2026) reproduces pain/allodynia via DRG targeting. If ME/CFS GPCR AAbs are functionally validated, ME/CFS IgG passive transfer should produce autonomic dysfunction (reduced HRV, orthostatic intolerance) in mice — a complementary phenotype to FM pain transfer. Prediction: \(\beta_2\)-AAb-positive ME/CFS IgG injected into mice causes HRV reduction (telemetry) and exercise intolerance (treadmill); pre-adsorption with \(\beta_2\)-AR protein abolishes autonomic phenotype. Cross-injection: FM IgG → pain; ME/CFS IgG → autonomic; FM+ME/CFS IgG → both (additive). (Azcue et al. 2026) (Goebel et al. 2021) (Santos Guedes de Sa 2026).
Certainty: 0.42. Sjögren syndrome anti-M3 muscarinic AAbs cause sicca symptoms (dry mouth/eyes) but some studies show paradoxically better cognition in M3-AAb-positive patients. The positive M1/M3/M4 AAb-cognition correlation in ME/CFS (Azcue et al. 2026) may share this paradox. Both conditions may involve CB1-mAChR heterodimer cross-activation in hippocampus — same AAbs cause peripheral pathology (dryness in Sjögren, autonomic dysfunction in ME/CFS) but central neuroprotection (cognitive benefit in both). Prediction: M3-AAb epitope mapping distinguishes Sjögren glandular-epitopes from ME/CFS neuronal-epitopes; cognitive testing shows positive M3-AAb – cognition correlation in both conditions. (Azcue et al. 2026) (Blaes, Wallukat, et al. 2011).
Certainty: 0.38. Graves disease anti-TSHR AAbs (pathogenic, Gs-coupled) target a receptor structurally homologous to \(\beta_2\)-AR. Molecular mimicry between TSHR and \(\beta_2\)-AR epitopes could produce cross-reactive GPCR AAbs, though this would predict hyperthyroid features not present in ME/CFS (patients are euthyroid). Prediction: \(\beta_2\)-AAb-positive ME/CFS patients have low-titer anti-TSHR AAbs below Graves diagnostic threshold and normal TSH/T4 despite \(\beta_2\)-AAb; competitive inhibition shows TSHR protein does not block \(\beta_2\)-AAb binding → no cross-reactivity. Likely independent autoantibody specificities. (Azcue et al. 2026).
Certainty: 0.52. Vernino 2022 (n=116 POTS, standard ELISA) failed to replicate GPCR AAbs while Loebel/Sotzny/Azcue find positives using CellTrend ELISA. Conflict likely reflects both assay sensitivity differences (CellTrend more sensitive to low-titer/low-affinity binding) and genuine POTS/ME/CFS subtype heterogeneity — some patients have GPCR AAbs, others do not. Prediction: \(\beta_2\)-AAb-positive ME/CFS patients have higher POTS prevalence (orthostatic HR increase >30 bpm) than \(\beta_2\)-AAb-negative; immunoadsorption improves POTS symptoms only in \(\beta_2\)-AAb-positive subgroup; same samples analyzed by Vernino’s vs Azcue’s methods show different positivity rates. (Azcue et al. 2026) (Stein et al. 2025).
(Certainty: 0.30.) Heat stroke involves gut-derived endotoxin translocation triggering systemic inflammation and HSP70 depletion — both documented features of ME/CFS pathophysiology. Stanculescu et al. (2021) identified 9 shared mechanisms; the HSP70-endotoxin axis may be the most tractable therapeutic target. If ME/CFS involves chronic low-grade endotoxemia perpetuating HSP70 deficiency, pre-treatment with gut barrier support before HSP70 induction could amplify thermal therapy benefit. Falsifiable: ME/CFS patients with elevated LPS (above 0.2 EU/mL) show blunted HSP70 induction (below 30% of healthy response); endotoxin binders restore inducibility. No ME/CFS endotoxin-HSP70 data (Stanculescu et al. 2021).
(Certainty: 0.25.) ICU survivors often develop persistent thermoregulatory dysautonomia with documented HSP70 depletion from critical illness. ME/CFS may follow an analogous trajectory: post-infectious HSP70 depletion that fails to recover spontaneously. The ICU literature provides HSP70 repletion protocols (gradual thermal conditioning) that could inform ME/CFS treatment, though the chronicity differs (ICU: weeks to recovery; ME/CFS: years of depletion). Falsifiable: ME/CFS patients with post-infectious onset show greater HSP70 deficit (below 50% of control) than gradual-onset patients; recovery rate is slower (12 vs 4 weeks) compared to post-ICU patients. No ME/CFS post-infectious HSP70 trajectory data.
(Certainty: 0.20.) Sickle cell disease involves ET-1-mediated vasoconstriction contributing to vaso-occlusive crises; bosentan has been trialed for this indication at the same PAH dose (125 mg BID). If ME/CFS ET-1 elevation produces analogous vasomotor dysfunction, sickle cell dosing and safety data provide a precedent. However, risk-benefit for non-life-threatening thermoregulatory symptoms is substantially less favorable than for vaso-occlusive crisis prevention. Falsifiable: ME/CFS patients with elevated ET-1 show microvascular rarefaction on nailfold capillaroscopy proportional to ET-1 level. No ME/CFS ET-1 antagonist data. Falsified if nailfold capillaroscopy shows no correlation (r below 0.3) between ET-1 levels and microvascular density in ME/CFS, indicating ET-1 elevation is not the primary driver of microvascular pathology.
(Certainty: 0.20.) Diabetic autonomic neuropathy causes vascular denervation detectable as abnormal foot temperature gradients (toe-to-sole temperature difference above 3°C vs control 1°C). ME/CFS may involve milder but analogous microvascular denervation. Daily infrared foot thermography (a 20 USD consumer device) could identify ME/CFS patients with significant vascular denervation who would benefit from vasodilator support rather than thermal training. Falsifiable: ME/CFS patients show foot temperature gradients above 2°C versus controls and reduced 24-hour skin temperature variability (amplitude reduced by more than 40%); thermography-measured denervation predicts poor response to vasomotor training. No ME/CFS foot thermography studies.