Peanut-specific Immunoglobulin G4 (psIgG4)

Peanut-specific Immunoglobulin G4 (psIgG4) is a subclass of IgG antibodies that plays a pivotal role in the development of clinical tolerance and desensitization in individuals with peanut allergy. Unlike allergen-specific IgE, which triggers immediate hypersensitivity reactions upon exposure, psIgG4 acts as a protective 'blocking antibody' by competing for the same epitopes on peanut allergens such as Ara h 2 and Ara h 6. This competition prevents IgE-mediated cross-linking of high-affinity receptors (FcεRI) on mast cells and basophils, thereby inhibiting the release of inflammatory mediators. Furthermore, psIgG4 can actively suppress allergic inflammation by co-engaging the inhibitory receptor FcγRIIb, which recruits phosphatases to dampen cellular activation. In clinical practice, psIgG4 levels and the psIgG4/IgE ratio are widely used as biomarkers to monitor the efficacy of allergen immunotherapies, including oral (OIT), sublingual (SLIT), and epicutaneous (EPIT) treatments. Recent therapeutic developments, such as the recombinant antibody cocktail IGNX001, aim to leverage these protective properties by providing passive immunization to rapidly protect allergic individuals from accidental exposure.

Other names

Peanut-specific IgG4psIgG4Blocking antibodyAntigen-specific IgG4Peanut-specific IgG

Drugs such as oral or epicutaneous immunotherapies induce the production of peanut-specific IgG4 by promoting B cell class switching through chronic, low-dose allergen exposure. Recombinant antibody therapies like IGNX001 provide passive protection by directly introducing high-affinity peanut-specific IgG4, which competes with endogenous IgE for allergen binding and co-engages the inhibitory receptor FcγRIIb on effector cells to suppress degranulation.