Pathogenic effects of bullous pemphigoid autoantibodies on rabbit corneal epithelium.

Abstract

A B S T R A C T Bullous pemphigoid (BP) is associated with circulating autoantibodies reactive with an antigen(s) of the basement membrane zone (BMZ) of skin and mucosae. The pathogenicity of these autoantibodies, although suspected, is unconfirmed. We have investigated the effects of BP autoantibodies on a closely related tissue, the corneal epithelium of the rabbit. IgG fractions from the sera of seven patients with BP were purified by (a) ammonium sulfate precipitation, (b) ion exchange chromatography, or (c) gel filtration. Control IgG was prepared by ion exchange chromatography of pooled normal human gamma globulins. 32 rabbits received corneal intrastromal injections of BP IgG fractions (50 gl, 0.95-2.05 mg total dose) in one eye, and control IgG (50 ,ul, 1.8 mg)in the contralateral cornea. 28 of 32 BP IgG injections produced corneal inflammatory lesions, 10 of which developed visible blisters. Histologically, lesions showed polymorphonuclear cells clustering along the BMZ, and subepithelial blister formation. Immunofluorescence showed in vivo bound IgG and C3 at the BMZ. The intensity of inflammation was dose dependent and correlated often with in vitro complement fixation titers of the fractions. None of 32 corneas injected with control IgG became inflamed. BP IgG fractions injected intradermally into the ear skin of rabbits failed to produce inflammation. This may be due to slow clearance of IgG in the cornea, and optimal binding by the corneal epithelium. The intracorneal injections of BP IgG reproduce the clinical, histological, and immunological features of BP. This study provides evidence that BP autoantibodies are pathogenic.

A passive transfer model of the organ-specific autoimmune disease, bullous pemphigoid, using antibodies generated against the hemidesmosomal antigen, BP180.

“…Gammon and Briggaman (36), however, could not reproduce these findings. Our laboratory demonstrated that local intrastromal injections of BP IgG into rabbit corneas induced separation ofthe epithelium from the stroma and migration ofneutrophils into the epithelial-stromal junction (37). Contralateral corneas injected with normal human IgG showed no inflammatory changes.…”

Human autoantibodies against the 230-kD bullous pemphigoid antigen (BPAG1) bind only to the intracellular domain of the hemidesmosome, whereas those against the 180-kD bullous pemphigoid antigen (BPAG2) bind along the plasma membrane of the hemidesmosome in normal human and swine skin.

“…its diagnosis. The binding of these autoantibodies to antigens located in the BMZ plays an important role in the pathogenesis ofblister formation in BP (2)(3)(4). BP antigens are normal components of the hemidesmosome complex of the BMZ, which are thought to be important not only in the pathogenesis of BP but also in dermoepidermal adhesion.…”

Human IgG1 Monoclonal Antibody against Human Collagen 17 Noncollagenous 16A Domain Induces Blisters via Complement Activation in Experimental Bullous Pemphigoid Model

“…Circulating autoantibodies target human type XVII collagen (human collagen 17 [hCOL17]), also known as BP Ag 2 (BPAG2) or BP180, which is a major component in hemidesmosome-anchoring filament complexes at the epidermal basement membrane zone (BMZ) (3)(4)(5)(6)(7)(8)(9). The major pathogenic epitope of BP autoantibodies is present at the extracellular noncollagenous 16A (NC16A) domain, which has distinctive diversity among different species (10)(11)(12). Deposition of anti-hCOL17 autoantibodies at the BMZ triggers sequential inflammatory cascades, including complement activation, degranulation of dermal mast cells, infiltration of eosinophils and neutrophils, and subepidermal blister formation elicited by proteinases derived from the inflammatory cells (13)(14)(15)(16)(17).…”