A combination of pemphigus foliaceus IgG monoclonal antibodies promotes desmoglein 1 clustering which induces synergistic pathogenic effect

Pemphigus foliaceus (PF) is an autoimmune blistering disease caused by anti-desmoglein1 (Dsg1) IgG antibodies (Abs). Pathogenic and non-pathogenic anti-Dsg1 monoclonal Abs (mAbs) were previously isolated as single chain variable fragments (scFvs) by phage display. However, it is unknown how each anti-Dsg1 mAb works for blister formation under polyclonal condition in vivo. In this study, we focused on the difference of a single mAb and a combination of mAbs on blister formation in the aspect of the Dsg1 distribution, desmosomal structure by using organ culture human skin injection assay. At first we created IgG form antibodies from scFv to reflect patient serum condition. A single pathogenic anti-Dsg1 IgG mAb caused subcorneal blister after 22 h injection and immunofluorescence showed IgG mAb deposited and Dsg1 localized linearly at the cell surfaces of keratinocytes. When a pathogenic and a non-pathogenic anti-Dsg1 mAbs were injected together, IgG deposits and Dsg1 localization showed an aberrant granular pattern at basal and spinous layers. This Dsg 1 clustering needed cross-linking of Dsg1 and trans-interaction blocking by a pathogenic IgG Ab. Electron microscopy revealed that a combination of pathogenic and non-pathogenic anti-Dsg1 mAbs shortened desmosome length more than a single mAb at the basal and spinous layers. In addition, dissociation assay showed a combination of pathogenic and non-pathogenic mAbs inhibited cell adhesion of keratinocytes more than a single pathogenic mAb. These findings indicated that a combination of PF mAbs induced Dsg1 clustering which may cause desmosome morphology change and promote loss of cell adhesion of keratinocytes synergistically. In conclusion, polyclonal condition of the anti-Dsg 1 Ab influences the pathogenicity in PF.