According to Bhol and Ahmed, pemphigus vulgaris is a potentially fatal autoimmune mucocutaneous disease associated with production of IgG autoantibodies to desmoglein 3, a 130 kDa epidermal protein. To further characterize the epitope(s) of pemphigus vulgaris antigen we established two human-human hybridoma by fusion of the peripheral blood mononuclear cells with a human and mouse heterohybridoma. These hybridomas designated as MAb Dsg-3: 06 and MAb Dsg-3: 10 and stable in culture and demonstrated yield of monoclonal antibodies specific for pemphigus vulgaris.
Immunofluorescence, immunoblot, ELISA assays demonstrated that both the monoclonal antibodies bind to the intercellular cement substance and to 130 kDa protein present in the skin and specifically binds to recombinant desmoglein 3 protein, but not to desmoglein 1 protein. The IgG subclass distribution study demonstrated that both the antibodies are of IgG1 subclass in nature. Both the antibodies were non-pathogenic as demonstrated in vitro by their inability to produce acantholysis in normal human skin in organ culture or in vivo by the induction of disease in neonatal BALB/c mice. The relevance and value of these monoclonal antibodies in the pathogenesis of pemphigus vulgaris is discussed.
Doctors Mao, Choi, and Payne from the University of Pennsylvania’s Department of Dermatology discovered in 2009 calcium-induced desmosome assembly, treatment of primary human keratinocytes with pathogenic monovalent anti-Dsg3 mAbs produced from a PV patient causes a decrease of Dsg3 and desmoplakin but not desmocollin (Dsc) 3 in the Triton-insoluble fraction of cell lysates within 2 hours.
Immunofluorescence and antibody ELISA studies suggest that pathogenic mAbs cause internalization of cell-surface Dsg3 but not Dsc3 through early endosomes. Electron microscopy demonstrated a lack of well-formed desmosomes in keratinocytes treated with pathogenic compared to nonpathogenic mAbs. In contrast, pathogenic mAbs caused late depletion of Dsg3 from preformed desmosomes at 24 hours, with effects on multiple desmosomal proteins including Dsc3 and plakoglobin. Together, these studies indicate that pathogenic PV mAbs specifically cause internalization of newly synthesized Dsg3 during desmosome assembly, correlating with their pathogenic activity. Monovalent human PV anti-Dsg mAbs reproduce the effects of polyclonal PV IgG on Dsg3 and will facilitate future studies to further dissect the cellular mechanisms for the loss of cell adhesion in pemphigus.