Antibodies to desmogleins 1 and 3, but not to BP180, induce blisters in human skin grafted onto SCID mice.

Pemphigus and bullous pemphigoid (BP) are blistering skin diseases associated with IgG autoantibodies to desmosomal and hemidesmosomal components. When autoantibodies to desmogleins 1 and 3 from patients with pemphigus foliaceus (PF) and pemphigus vulgaris (PV) or rabbit antibodies against the murine hemidesmosomal component BP180 are passively transferred into neonatal mice, they induce blisters in the skin of the mice. To develop an animal model that would duplicate the findings in the skin of the patients more closely, full-thickness human skin from healthy volunteers was grafted onto SCID mice. Injection of the purified IgG fraction from the serum of PF and PV patients led to subcorneal and suprabasal splits in the human grafts and human IgG was deposited intercellularly in the upper and lower layers of the epidermis, respectively. Interestingly, anti-BP180 autoantibodies purified from the serum of BP patients and from a rabbit immunized with recombinant human BP180 strongly bound to the basement membrane zone of the grafts (n=32), fixed murine complement, led to the recruitment of neutrophils to the upper dermis of the graft, but did not induce subepidermal blisters. We report a novel experimental model for PF and PV which should greatly facilitate further studies to dissect the immunopathological mechanisms in these diseases. Specifically, this model can be used to identify pathogenically relevant epitopes on human desmogleins 1 and 3 and to develop novel strategies for the treatment of pemphigus.

Autoantibodies in anti-p200 pemphigoid stain skin lacking laminin 5 and type VII collagen.

We report the case of a patient with a widespread bullous skin disease and linear deposits of IgG and C3 at the dermal-epidermal junction using direct immunofluorescence microscopy. Indirect immunofluorescence analysis demonstrated circulating IgG autoantibodies that stained, like autoantibodies to laminin 5 and type VII collagen, the dermal side of 1 mol L-1 NaCl-split human skin. By immunoblotting dermal extracts, the patient's serum, like serum samples from two control patients, reacted with a 200-kDa protein. Using immunoelectron microscopy, the serum labelled a component of the lower lamina lucida, but not the lamina densa/sublamina densa region, distinguishing this from the type VII collagen localization pattern. By immunofluorescence microscopy on skin sections from patients lacking either laminin 5 (Herlitz's epidermolysis bullosa) or type VII collagen (recessive dystrophic epidermolysis bullosa of Hallopeau-Siemens), the patient's serum retained reactivity with these test substrates. The patient's disease responded rapidly to the use of topical corticosteroids and lesions healed without scarring or milia formation. Our results provide strong evidence for the hypothesis that the 200 kDa autoantigen is different from laminin 5 and type VII collagen. For this new disease, we propose the designation 'anti-p200 pemphigoid'.

Bullous pemphigoid of childhood: autoantibodies target the same epitopes within the NC16A domain of BP180 as autoantibodies in bullous pemphigoid of adulthood.

BACKGROUND: Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease of the elderly that rarely occurs in children. Most adult BP serum samples react with epitopes within the NC16A domain of BP180, a glycoprotein of the cutaneous basement membrane zone. OBJECTIVES: To characterize the autoimmune response in childhood BP using recombinant forms of BP180 and to determine the subclass distribution of autoantibodies and their correlation with disease activity. OBSERVATIONS: Serum samples from 2 infants with BP, aged 4 and 5 months, reacted by immunoblot analysis with 4 epitopes clustered within the N-terminal 45 amino acids of the NC16A domain. The same 4 epitopes have previously been shown to be the target in adult BP. Childhood BP antibodies to BP180 NC16A belonged to IgG1, IgG2, IgG3, and IgG4 immunoglobulin subclasses. IgE reactivity was not detected. Serum levels of antibodies targeting BP180 NC16A paralleled disease activity as detected by enzyme-linked immunosorbent assay. CONCLUSIONS: The fine specificity of autoantibodies to BP180 is the same in BP of childhood and adulthood. Childhood BP is a true variant of BP.

IgG4 and IgE are the major immunoglobulins targeting the NC16A domain of BP180 in Bullous pemphigoid: serum levels of these immunoglobulins reflect disease activity.

BACKGROUND: Bullous pemphigoid (BP) is an autoimmune blistering disease associated with autoantibodies against the hemidesmosomal glycoprotein BP180. The noncollagenous (NC)16A domain of BP180 has recently been shown to harbor major antigenic sites recognized by BP sera. OBJECTIVE: The purpose of this study was to characterize the subclass distribution and fine specificities of autoantibodies to BP180 NC16A present in the circulation of patients with BP before, and during the course of, therapy for this disease. METHODS: Eighteen BP sera were analyzed by immunoblotting and enzyme-linked immunosorbent assay for the presence of IgG1, IgG2, IgG3, IgG4, and IgE reactive with various sites on the BP180 NC16A domain. The sera were collected before treatment was started and at 4- and 8-week time points after initiation of treatment. RESULTS: We identified IgG4 and IgE as the major immunoglobulins that preferentially react with two distinct epitopes (MCW-1 and MCW-2) within BP180 NC16A. Levels of these autoantibodies correlated with disease activity in BP. During the course of disease, no change was observed with regard to the immunoglobulin subclass predominantly reacting with BP180 NC16A or the specific epitopes within this domain. CONCLUSION: Our data demonstrate that remission of BP is paralleled by a decrease of serum levels of IgE and the different IgG subclasses reactive with BP180 NC16A.

Autoantibodies in a subgroup of patients with linear IgA disease react with the NC16A domain of BP1801.

Linear IgA disease is an autoimmune subepidermal blistering disease characterized by IgA deposits at the cutaneous basement membrane zone. IgA antibodies from linear IgA disease sera react with antigens of 97 kDa (LABD97) and 120 kDa (LAD-1), both of which appear to be fragments of the extracellular domain of bullous pemphigoid 180 (type XVII collagen). The aim of this study was to determine whether linear IgA disease sera react with the immunodominant region of BP180 (NC16A domain), which is a major target of IgG autoantibodies produced by patients with bullous pemphigoid. Indeed, 11 of 50 linear IgA disease sera were found to contain IgA autoantibodies that recognized a recombinant form of NC16A by immunoblotting. The same sera also reacted with NC16A by enzyme-linked immunosorbent assay. An epitope mapping analysis uncovered four linear IgA disease-associated epitopes located within the 45 amino acid N-terminal stretch of NC16A, all of which were previously identified as antigenic sites targeted by bullous pemphigoid autoantibodies. Eight of the linear IgA disease sera that were reactive with NC16A also recognized LAD-1 secreted by the SCC-25 cell line, and five sera recognized BP180 extracted from keratinocytes. Linear IgA disease sera depleted of reactivity to NC16A by immunoadsorption continued to react with both the LAD-1 antigen and BP180 by immunoblotting and with the basement membrane zone by indirect immunofluorescence microscopy. Our results demonstrate that IgA autoantibodies from a subset of linear IgA disease patients react with the same sites on BP180 that are targeted by IgG autoantibodies in bullous pemphigoid.