IgG4 as The Predominant Autoantibody In Sera From Patients With Active State of Pemphigus Vulgaris

Background: Pemphigus vulgaris (PV) is an autoimmune blistering disease of the skin and mucous membranes caused by pathogenic antibodies. The aim of this study was to determine the antigen-specific subclasses of IgG present in the sera of Iranian patients with the active form of the disease and those in remission. Methods: Serum samples from 75 patients with the clinical presentation of PV and 50 normal healthy subjects were investigated after informed consent to use these samples for investigational use. Distribution of the IgG subclass autoantibody was studied by using specific monoclonal antibodies to IgG1, IgG2, IgG3 and IgG4 in 17 patients with active form of disease, and 20 patients in remission with an indirect ELISA based method. Results: The mean optical densities (OD) for IgG1−IgG4 (1.22, 0.63, 0.55, 1.11) versus the controls (0.38, 0.26, 0.37, 0.41) showed significant differences (P = 0.0001) for IgG1 and IgG4 in all PV patients. The mean OD of specific IgG1 autoantibody (0.52) compared with normal controls (0.38) was found to be significant in patients in remission (P = 0.02), while the titres of IgG4 autoantibody were not significantly different between patients in remission and control individuals (OD = 0.46 versus 0.41) (P = 0.37). Conclusion: Elevated levels of IgG4 in patients with active disease, and of IgG1 in patients in remission, point to an important finding regarding the pathogenesis of autoantibodies in PV patients. The finding concludes that the detection of IgG4 in PV patients is pathogenic and should be considered as a clinical marker, while elevated IgG1 autoantibody may be produced within the repertoire of natural and non-pathogenic autoantibodies.

Keywords:  Autoimmune disease, Pemphigus vulgaris, IgG4