A 28-year-old woman presents with a 6-week history of recurrent blistering on the dorsal hands, forearms, and face, triggered by sun exposure. Examination reveals grouped vesicles and erosions on erythematous bases. Serum testing shows IgG antibodies against endomysial antigen. Skin biopsy demonstrates subepidermal blister with neutrophilic microabscesses at the dermal–epidermal junction. Which of the following mechanisms BEST explains the pathophysiology of this condition?