Erythema Multiforme Associated Human Autoantibodies Against Desmoplakin I and II: Biochemical Characterization and Passive Transfer Studies Into Newborn Mice

Abstract

The demonstration of circulating autoantibodies directed against the constitutive desmosomal plaque proteins desmoplakin (dp) I and II in mucocutaneous lesions in a subset of patients with erythema multiforme major, suggests that humoral immune mechanisms may play a role in the pathogenesis of this severe skin disease. In this study we identified a specific peptide sequence--YSYSYS--representing an antigenic binding site for the human autoantibodies. This epitope is localized at the extreme carboxy terminal domain of dp thought to be responsible for the assembly of keratin filaments with desmosomes. To test the possibility whether these antibodies may exert any pathologic effects in vivo, human autoantibodies were affinity purified on a corresponding synthetic peptide matrix and peptide-specific antibodies were raised in rabbits. After repeated subcutaneous injections into newborn mice, affinity-purified human autoantibodies and anti-peptide rabbit IgG were detected on desmosomal plaques of keratinocytes overlying the injection site. Histologic and electron microscopic examinations showed hydropic degeneration of basal and suprabasal keratinocytes, dyskeratosis, signs of suprabasal acantholysis, and keratin filaments detached from the desmosomal plaques clumping around the nucleus. We demonstrate that autoantibodies are directed to an epitope within a dp domain crucial for the interaction of keratin filaments with desmosomes, and, when injected subcutaneously into newborn mice, produce pathologic changes. These findings imply that autoantibodies to dp could impair the function of desmosome-keratin filament complexes suggesting a pathogenic role in vivo.

Development of antigen-specific ELISA for circulating autoantibodies to extracellular matrix protein 1 in lichen sclerosus

“…In fact, several reports demonstrate penetration of IgG autoantibody into living cells (19,20). Notably in keratinocytes, by using passive transfer and in vitro cell culture systems, a series of recent investigations have also demonstrated that IgG autoantibodies to desmoplakin I/II, entirely intracellular desmosomal antigens, can get into living cells and reach the target antigens (21)(22)(23). Moreover, anti-nuclear IgG antibodies from patients with systemic lupus erythematosus have been shown to penetrate into living epithelial cells via receptor-mediated endocytosis and subsequently localize to the corresponding intracellular target antigens (24).…”

Expression of FcRn, the MHC Class I-Related Receptor for IgG, in Human Keratinocytes

“…Generation of anti-FcRn Ab An affinity-purified peptide-specific Ab to FcRn a2-extracellular domain was generated according to the methods as described in detail earlier (Foedinger et al, 1998). The 14 amino acids sequence peptide LNGEEFMNFDLKQG out of the a2-extracellular domain of human FcRn was used as antigen to raise a peptide-specific rabbit anti-FcRn Ab (by Charles River, Kisslegg, Germany).…”

Severe sequelae of erythema multiforme: three cases

“…Anti-plakin auto-antibodies are found in some patients. 1 EM must be distinguished from Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which are drug induced in most cases. [2][3][4][5] However, mucous membrane (MM) lesions of EM major (EMM) are clinically similar to those of SJS/TEN and literature remains confusing between both diseases.…”

“…We identified that the loss of inositol polyphosphate-5-phosphatase (INPP5A) may play a role in the development and progression of cutaneous squamous cell carcinoma (SCC). 1 Loss of INPP5A has been previously linked to cancer development and progression. 2 Inositol signalling pathways are involved in intracellular calcium release, membrane trafficking, chemotaxis, ion channel activity and many other nuclear functions.…”