Pathophysiology of dermatitis herpetiformis: a model for cutaneous manifestations of gastrointestinal inflammation

Walnut antigens can trigger autoantibody development in patients with pemphigus vulgaris through a "hit-and-run" mechanism

BACKGROUND

Environmental factors, as well as genetic predisposition, are known to be critical for the development of autoimmunity. However, the environmental agents that trigger autoimmune responses have remained elusive. One possible explanation is the "hit-and-run" mechanism in which the inciting antigens that initiate autoimmune responses are not present at the time of overt autoimmune disease.

OBJECTIVE

After our previous findings that some allergens can incite autoimmune responses, we investigated the potential role of environmental allergens in triggering autoantibody development in patients with an autoimmune skin disease, pemphigus vulgaris (PV).

METHODS

Revertant/germline mAbs (with mutations on variable regions of heavy and light chains reverted to germline forms) of 8 anti-desmoglein (Dsg) 3 pathogenic mAbs from patients with PV were tested for reactivity against a panel of possible allergens, including insects, pollens, epithelia, fungi, and food antigens.

RESULTS

All the PV germline mAbs were reactive to antigens from walnut, including the well-known allergen Jug r 2 and an uncharacterized 85-kDa protein component. Sera from patients with PV contained significantly greater levels of anti-Dsg3 autoantibodies than walnut-specific antibodies, suggesting that the autoreactive B-cell response in patients with PV might be initially triggered by walnut antigens but is subsequently driven by Dsg3.

CONCLUSION

Our findings suggest that walnut antigens/allergens can initiate autoantibody development in patients with PV through a "hit-and-run" mechanism. The revertant/germline mAb approach might provide a paradigm for the etiological study of other allergic and autoimmune diseases.

Consensus on the treatment of autoimmune bullous dermatoses: dermatitis herpetiformis and linear IgA bullous dermatosis - Brazilian Society of Dermatology

Dermatitis herpetiformis and linear IgA bullous dermatosis are autoimmune diseases that present with pruritic urticarial papules and plaques, with formation of vesicles and blisters of subepidermal location, mediated by IgA antibodies. Mucosal lesions are present only in linear IgA bullous dermatosis. The elaboration of this consensus consisted of a brief presentation of the different aspects of these dermatoses and, above all, of an updated literature review on the various therapeutic options that were discussed and compared with the authors' experience, aiming at the treatment orientation of these diseases in Brazil. Dermatitis herpetiformis is a cutaneous manifestation of celiac disease, and can be controlled with a gluten-free diet and dapsone. On the other hand, linear IgA bullous dermatosis arises spontaneously or is triggered by drugs, and can be controlled with dapsone, but often requires the association of systemic corticosteroids and eventually immunosuppressants.

Celiac disease and autoimmune-associated conditions

Celiac disease (CD) is frequently accompanied by a variety of extradigestive manifestations, thus making it a systemic disease rather than a disease limited to the gastrointestinal tract. This is primarily explained by the fact that CD belongs to the group of autoimmune diseases. The only one with a known etiology is related to a permanent intolerance to gluten. Remarkable breakthroughs have been achieved in the last decades, due to a greater interest in the diagnosis of atypical and asymptomatic patients, which are more frequent in adults. The known presence of several associated diseases provides guidance in the search of oligosymptomatic cases as well as studies performed in relatives of patients with CD. The causes for the onset and manifestation of associated diseases are diverse; some share a similar genetic base, like type 1 diabetes mellitus (T1D); others share pathogenic mechanisms, and yet, others are of unknown nature. General practitioners and other specialists must remember that CD may debut with extraintestinal manifestations, and associated illnesses may appear both at the time of diagnosis and throughout the evolution of the disease. The implementation of a gluten-free diet (GFD) improves the overall clinical course and influences the evolution of the associated diseases. In some cases, such as iron deficiency anemia, the GFD contributes to its disappearance. In other disorders, like T1D, this allows a better control of the disease. In several other complications and/or associated diseases, an adequate adherence to a GFD may slow down their evolution, especially if implemented during an early stage.

Molecular diagnosis of autoimmune blistering diseases

Autoimmune bullous diseases are the best-characterized autoimmune skin diseases. Molecular diagnosis of these diseases has become possible due to the identification of their target autoantigens over the past three decades. In this review, we summarize methodology for categorizing autoimmune bullous diseases by means of combinations of direct and indirect immunofluorescence techniques using normal human skin sections, rat bladder sections and COS7 cells transfected with desmocollins 1-3 encoded vectors, enzyme-linked immunosorbent assays and immunoblotting with normal human epidermal extracts, dermal extracts, purified proteins from cell cultures and recombinant proteins.

Dermatitis herpetiformis: Novel advances and hypotheses

Dermatitis herpetiformis (DH) is a gluten-sensitive autoimmune blistering disorder with a chronic-relapsing course. Very recently, several Authors reported atypical cases of patients with DH, suggesting that different clinical subsets may exist at least among different ethnicities and that the classical picture of DH probably need a significant revision. Moreover, different pathogenetic aspects of the disease are currently under investigation, including the role of epidermal transglutaminase, apoptosis and inflammatory cells in the occurrence of skin lesions, in order to explain why only a subgroup of celiac patients will develop DH. Finally, although gluten-free diet is still regarded as the only curative approach to the disease, it is very hard to comply with and even small amounts of gluten can re-activate the disease. Therefore, different therapeutical approaches for the spectrum DH/celiac disease are still under investigation. In the present paper, the most recent advances in DH will be discussed, and a novel interpretation of the disease based on the data emerging from the Literature will be proposed.

Recent advances in dermatitis herpetiformis

Dermatitis herpetiformis is an autoimmune bullous disease that is associated with gluten sensitivity which typically presents as celiac disease. As both conditions are multifactorial disorders, it is not clear how specific pathogenetic mechanisms may lead to the dysregulation of immune responses in the skin and small bowel, respectively. Recent studies have demonstrated that IgA and antibodies against epidermal transglutaminase 3 play an important role in the pathogenesis of dermatitis herpetiformis. Here, we review recent immunopathological progress in understanding the pathogenesis of dermatitis herpetiformis.

Dermatitis herpetiformis: from the genetics to the development of skin lesions

Dermatitis herpetiformis (DH) is a rare autoimmune disease linked to gluten sensitivity with a chronic-relapsing course. It is currently considered to be the specific cutaneous manifestation of celiac disease (CD). Both conditions are mediated by the IgA class of autoantibodies, and the diagnosis of DH is dependent on the detection of granular deposits of IgA in the skin. There is an underlying genetic predisposition to the development of DH, but environmental factors are also important. This paper describes these different factors and discusses the known mechanism that lead to the development of skin lesions.