UPDATE ON IGg4 AUTOIMMUNE DISEASES
- Inga Koneczny, Austria
Abstract
Background and Aims
IgG4 autoimmune diseases are characterized by the presence of antigen-specific autoantibodies of IgG4 subclass, and contain well-characterised diseases such as MuSK myasthenia gravis, pemphigus and thrombotic thrombocytopenic purpura. Recently several new diseases were identified, and by now at least 21 antigens associated with IgG4 subclass are known. The IgG4 subclass is considered as immunologically inert and functionally monovalent The pathogenicity of IgG4 autoantibodies can be validated using our recently published classification system.
Methods
Using literature research, autoimmune diseases associated with IgG4 autoantibodies were identified. Clinical and immunological research data of identified diseases were critically reflected and the pathogenicity of the IgG4 autoantibodies was analysed using the classification system for IgG4 autoantibodies.
Results
As a result, one new class II and six new class III IgG4 autoimmune diseases were identified. New research data allowed a re-classification of Neurofascin-155 antibody associated CIDP as class I IgG4 autoimmune disease. IgG4 autoimmune diseases were found to be restricted to four distinct organs: 1) the central and peripheral nervous system, 2) the kidney, 3) the skin and mucous membranes and 4) the vascular system or soluble antigens in the blood circulation.
Conclusions
In conclusion, there are to date six class I (verified), five class II (likely) and ten class III IgG4 autoimmune diseases, of which five are class IIIa, with insufficient data and five class IIIb, which support pathogenic entities other than IgG4. The pathogenicity of IgG4 in IgG4 autoimmune diseases is associated with blocking of enzymatic activity or protein-protein interaction of their target antigen