Pemphigus vulgaris is a Type II hypersensitivity characterized by autoantibodies against which protein?

• A. Collagen IV in basement membrane
• B. Desmoglein (desmosomal cadherin) in keratinocytes
• C. Keratin
• D. Desmocollin in desmosomes

Answer: (B)

Desmoglein in desmosomes of keratinocytes is the target in pemphigus vulgaris, and this is what makes it a Type II hypersensitivity. Autoantibodies binding desmoglein disrupt the desmosomes that hold keratinocytes together, causing loss of cell–cell adhesion (acantholysis) and resulting in intraepidermal blisters. This mechanism explains the flaccid bullae and mucosal lesions typical of the disease, as well as the intercellular IgG seen on immunofluorescence in a net-like pattern. Collagen IV is a basement membrane component and relates to other blistering conditions, keratin is an intracellular protein not exposed to a conventional autoantibody attack here, and desmocollin is another desmosomal protein but the classic Pemphigus vulgaris target is desmoglein (primarily Dsg3, sometimes Dsg1).