The enigma of the Liverpool passive transfer model (2021) and the IgG4 - Quinolinic Acid vector in Fibromyalgia: A critical review

This paper resolves the interpretative paradox of the passive transfer murine model (2021). It is demonstrated that peripheral immunoglobulin G4 (IgG4) operates exclusively as a hermetic macromolecular vector that encapsulates the neurotoxin Quinolinic Acid within its internal interface (CH3 domain), while the other IgG subclasses remain functionally uninvolved due to their structural rigidity. Following the dissociation of its hinge region due to peripheral tissue acidosis (pH ≤ 6.4), the metabolite lodges in this proximal core through hydrophobic interactions stabilized by its two aromatic rings. The tremendously hydrophobic nature of this acceptor pocket repels surrounding aqueous solutions, preventing the release of the payload during conventional in vitro washing protocols and causing a methodological blindness in standard assays. The symptomatic remission at 21 days in the murine specimen responds strictly to the fineness of the inoculated dose and the expiration of the biological life cycle of the circulating heterologous IgG4, which degrades without an endogenous source of replenishment. A caotropic acid elution analytical protocol (pH ≤ 3.0) using LC-MS/MS is formalized to quantitatively release the metabolite and consolidate a definitive exclusion diagnostic biomarker for Fibromyalgia.