title: Non-pathogenic pemphigus foliaceus (PF) IgG acts synergistically with a directly pathogenic PF IgG to increase blistering by p38MAPK-dependent desmoglein 1 clustering.
abstract: BACKGROUND
  Pemphigus foliaceus (PF) is an autoimmune blistering disease caused by autoantibodies (Abs) against desmoglein 1 (Dsg1). PF sera contain polyclonal Abs which are heterogeneous mixture of both pathogenic and non-pathogenic Abs, as shown by isolation of monoclonal Abs (mAbs).
  
  
  OBJECTIVE
  To investigate how pathogenic and non-pathogenic anti-Dsg1 Abs contribute to blister formation in PF.
  
  
  METHODS
  Using organ-cultured human skin, we compared the effect of a single pathogenic anti-Dsg1 IgG mAb, a single non-pathogenic anti-Dsg1 IgG mAb, and their mixture on blister formation as analyzed by histology, subcellular localization of IgG deposits and desmosomal proteins by confocal microscopy, and desmosomal structure by electron microscopy. In addition, we measured keratinocyte adhesion by an in vitro dissociation assay.
  
  
  RESULTS
  24h after injection, a single pathogenic anti-Dsg1 IgG caused a subcorneal blister with IgG and Dsg1 localized linearly on the cell surface of keratinocytes. A single non-pathogenic anti-Dsg1 IgG bound linearly on the keratinocytes but did not induce blisters. A pathogenic and a non-pathogenic IgG mAb injected together caused an aberrant granular pattern of IgG and Dsg1 in the lower epidermis with blister formation in the superficial epidermis. Electron microscopy demonstrated that the mixture of mAbs shortened desmosomal lengths more than a single mAb in the basal and spinous layers. Furthermore, although Dsg1 clustering required both cross-linking of Dsg1 molecules by the non-pathogenic IgG plus a pathogenic antibody, the latter could be in the form of a monovalent single chain variable fragment, suggesting that loss of trans-interaction of Dsg1 is required for clustering. Finally, a p38MAPK inhibitor blocked Dsg1 clustering. When pathogenic strength was measured by the dissociation assay, a mixture of pathogenic and non-pathogenic IgG mAbs disrupted keratinocyte adhesion more than a single pathogenic mAb. This pathogenic effect was only partially suppressed by the p38MAPK inhibitor.
  
  
  CONCLUSIONS
  These findings indicate that a polyclonal mixture of anti-Dsg1 IgG antibodies enhances pathogenic activity for blister formation associated with p38MAPK-dependent Dsg1 clustering and that not only pathogenic antibodies but also non-pathogenic antibodies coordinately contribute to blister formation in PF.
authors.affiliation: Dermatology, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Dermatology, Toho University School of Medicine, Tokyo, Japan. Electronic address: ken.ishii@med.toho-u.ac.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Ishii
authors.affiliation: Dermatology, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shimizu
authors.affiliation: Dermatology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Yokouchi
authors.affiliation: Dermatology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Amagai
authors.affiliation: Dermatology, Ehime University School of Medicine, Ehime, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Shiraishi
authors.affiliation: Dermatology, Ehime University School of Medicine, Ehime, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Shirakata
authors.affiliation: Dermatology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Stanley
authors.affiliation: Dermatology, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ishiko
mesh_terms: D001323:Autoantibodies / Q000276:immunology*; D002448:Cell Adhesion; D051183:Desmoglein 1 / Q000276:immunology* / Q000378:metabolism; D003896:Desmosomes / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology*; D015603:Keratinocytes / Q000276:immunology / Q000502:physiology*; D008854:Microscopy, Electron; D009924:Organ Culture Techniques; D010392:Pemphigus / Q000097:blood / Q000276:immunology*; D061251:Primary Cell Culture; D011725:Pyridines / Q000494:pharmacology; D057127:Single-Chain Antibodies / Q000276:immunology*; D012867:Skin / Q000276:immunology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D001323:Autoantibodies; C495297:DSG1 protein, human; D051183:Desmoglein 1; D007093:Imidazoles; D007074:Immunoglobulin G; D011725:Pyridines; D057127:Single-Chain Antibodies; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole
keywords: Desmoglein 1; Desmoglein 1 clustering; Pemphigus foliaceus; p38MAPK signaling