Immunoglobulin G4 is prevailing over immunoglobulin G1 in autoimmunity of pemphigus and bullous pemphigoid: analysis of tissue-bound antibodies in active diseases

Introduction: Pemphigus and bullous pemphigoid (BP) are immune-mediated blistering diseases. Autoimmunity in these dermatoses is associated with stimulation of Th1/Th2 cells responsible for pathogenic autoantibodies production. Still, there is no consensus on the role of immuno globulin G (IgG) subclasses in pemphigus/BP pathogenesis. Aim of the study: To statistically analyze the IgG-, IgG1- and IgG4-positive results of direct immunofluorescence (DIF) test performed in patients with pemphigus and BP. Material and methods: Altogether, 117 specimens (pemphigus + BP) were included in this study. Frozen sections of skin/mucosa were subjected to DIE The IgG/IgG1/IgG4 FITC-labeled poly-/mono-clonal antibodies were used to analyze the subclass restriction. Results: Immunoglobulin G deposits were detected in 44 of 71, IgG1 in 34, IgG4 in 60 pemphigus biopsies. Immunoglobulin G deposits were detected in 8 of 46, IgG1 in 15, IgG4 in 36 BP biopsies. There are significant differences between number of positive vs. negative results regarding (i) IgG4 vs. IgG deposits, IgG4 vs. IgG1 deposits in both pemphigus and BP. (ii) IgG deposits in pemphigus vs. IgG deposits in BP. There are no significant differences between (i) IgG1 vs. IgG deposits in both pemphigus and BP, (ii) IgG1 deposits in pemphigus vs. IgG1 deposits in BP, (iii) IgG4 deposits in pemphigus vs. IgG4 deposits in BP. There are also significant differences between IgG1 strong/weak vs. IgG4 strong/weak in both pemphigus and BP. Conclusions: The fluorescence intensity of tissue-bound IgG4 is significantly higher than fluorescence intensity of IgG and IgG1 in both pemphigus and BP. what may suggest that IgG4 is the initial and predominant tissue-bound antibody subclass detected in these diseases.