IgG4 (Immunglobulin G4) are antibodies of class G and are the lowest fraction of IgG subclasses in the blood of healthy persons.
IgG4 is normally formed especially in allergic reactions or increase in a
The human immune system triggers formation of cytokines and IgG4 in a so
called T-cell mediated associated immune response (t helper cells type II). Patients, who
suffer from an IgG4-related disease, often show increased IgG4 levels in the serum whereby
enhanced IgG4 is not decisive for disease.
An increased IgG4 level can also be proven in diseases such as Churg-Strauss-Syndrome, allergic or parasitic disorders and chronic inflammatory diseases.
Based on the still limited knowledge, IgG4 related disease can not be precisely attributed to an autoimmune disease or allergic reaction.