Relationship Between Antigens and Igg Subclasses in Bullous Pemphigoid

Abstract

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized in part by the presence of tissue-bound and circulating antibodies (mostly of IgG) to the basement membrane zone (BMZ). We previously reported that IgG subclasses of BP antibodies were IgG₁, IgG₂ and IgG₄, and that only BP IgG₁ fixed complements. In this study, we examined whether BP IgG sub-classes bound to the same epitope of BP antigen or a different epitope. In an inhibition immunofluorescence studies, the complement fixing capability of IgG₁ was inhibited by the pretreatment with IgG₄ and partially inhibited by IgG₂. On immunoblot analysis, IgG₁ and IgG₄ were bound to the same MW of BP antigen. In enzyme-linked immunosorbent assay (ELISA), the binding capability of IgG subclass fractions from patients with BP to synthetic peptide PI-2, exceeding normal IgG subclass fractions was seen in five IgG₁, one IgG₂ and two IgG₄, from eight BP patients. The binding capability of IgG subclass fractions from the patients with BP to Pl-1, exceeding the normal IgG fractions was seen in two IgG₁, three IgG₂ and one IgG₄ from ten BP patients. On inhibition ELISA, the binding activity to Pl-2 of IgG₄ was partially inhibited by the pretreatment of IgG₁ and IgG₂. These findings suggest that BP IgG₁, IgG₂ and IgG₄ could bind to the same epitope though considerable variation occurred between patients.

Key Words:

• autoimmune bullous disease
• bullous pemphigoid
• anti-basement membrane zone antibody IgG subclass