Dermatitis herpetiformis: biochemical properties of the granular deposits of IgA in papillary dermis. Characterization of SDS-soluble IgA-like material and potentially antigen-binding IgA fragments released by pepsin

Dermatitis herpetiformis: close to unravelling a disease

Dermatitis herpetiformis is characterised by granular IgA precipitates in the papillary dermis. In contrast to other autoimmune blistering diseases, where tissue-deposited and circulating autoantibodies recognise the same target within the skin, in dermatitis herpetiformis a serum IgA reacting with a component of the healthy papillary dermis has not been detected. Recently, the antigenic specificity of pathognomic skin-bound IgA has been clarified: the immune precipitates contain epidermal transglutaminase, an enzyme not previously detected in the papillary region of normal skin. Furthermore, serum IgA in dermatitis herpetiformis has been found to bind epidermal transglutaminase. These findings may relate to the fact, that dermatitis herpetiformis is associated with gluten sensitive enteropathy, coeliac disease, which is characterised by IgA type autoantibodies to a closely related enzyme, tissue transglutaminase. The two transglutaminases are highly homologous, and therefore, cross reactivity of the two antibodies might explain why patients with gluten sensitive enteropathy, with or without skin disease, generally have serum autoantibodies to both enzymes. There is growing evidence that dermatitis herpetiformis should be considered as the skin manifestation of gluten sensitivity developing in those patients with mild coeliac disease, who produce epidermal transglutaminase autoantibodies of high avidity and affinity. Both the skin and the small bowel diseases are gluten dependent and are strongly associated with HLA DQ with no genetic differences to explain the two phenotypes. The question should be asked whether the rash in dermatitis herpetiformis is a classic autoimmune blistering disease or whether it has an immune complex basis, which is the most likely alternative.

25 years' experience of a gluten-free diet in the treatment of dermatitis herpetiformis

Gluten-free diets have been used in the treatment of patients with dermatitis herpetiformis in our department since 1967. Of the 212 patients with dermatitis herpetiformis attending between 1967 and 1992, 133 managed to take the diet, and 78 of these achieved complete control of their rash by diet alone. Of the remaining 55 patients taking a gluten-free diet, all but three were taking partial diets; over half of these patients managed to substantially reduce the dose of medication required. Of the 77 patients taking a normal diet, eight entered spontaneous remission, giving a remission rate of 10%; a further two patients who had been taking gluten-free diets were found to have remitted when they resumed normal diets. Loss of IgA from the skin was observed in 10 of 41 (24%) patients taking strict gluten-free diets. These patients had been taking their diets for an average of 13 years (range 5-24 years), and their rash had been controlled by diet alone for an average of 10 years (range 3-16 years). The advantages of a gluten-free diet in the management of patients with dermatitis herpetiformis are: (i) the need for medication is reduced or abolished; (ii) there is resolution of the enteropathy, and (iii) patients experience a feeling of well-being after commencing the diet. Thus, we propose that a gluten-free diet is the most appropriate treatment for patients with dermatitis herpetiformis.

Fc receptor function and circulating immune complexes in gluten sensitive enteropathy--possible significance of serum IgA

The capacity to clear IgG containing immune complexes from the circulation was studied in patients with coeliac disease (n = 13), dermatitis herpetiformis (n = 8), and coeliac disease with concomitant serum IgA deficiency (n = 4). A small group of patients with active ulcerative colitis (n = 4) was included as a bowel disease control group. Clearance was estimated by measuring the disappearance rate of a bolus dose of intravenously injected IgG coated autologous erythrocytes. The mean T1/2 of clearance was prolonged in both coeliac disease (86 (24) minutes) and dermatitis herpetiformis (111 (35) minutes), compared with healthy subjects (20 (5) minutes) and coeliac patients with concomitant serum IgA deficiency (T1/2 = 17 (6) minutes). Patients with ulcerative colitis had a prolonged clearance, with a T1/2 of 195 (63) minutes. Values of circulating immune complexes were measured by four assays; C1q binding and C3, IgG, and IgA containing immune complexes. C1q binding immune complexes were detected only in IgA deficient gluten sensitive enteropathy. Patients with coeliac disease and dermatitis herpetiformis had higher values of C3, IgG, and IgA containing immune complexes than control subjects and serum IgA deficient patients with coeliac disease. The clearance rate was inversely correlated to the amount of immune complexes for the subgroups of gluten sensitive enteropathy.

A simple method for elution of IgA deposits from the skin of patients with dermatitis herpetiformis

To better understand the role of autoimmunity in the pathogenesis of dermatitis herpetiformis, linear IgA bullous dermatosis or other skin disorders, the antigenic specificity of the immune reactants bound in vivo in the skin must be identified. In order to do so, one must first be able to elute these immune reactants from the skin. We describe here a simple method of eluting not only specifically bound IgG, but also IgA and other immunoglobulins and complement components from skin biopsy material. The method involves cutaneous washing of the entrapped serum proteins in PBS pH 7 and pH 5 buffers followed by specific immunoglobulin elutions at pH 3 and 2. The IgA deposits which could not be removed by this treatment were eluted by a combination of low pH (0.5 M citrate pH 2) and a chaotropic agent (2 M NaCl). The relative concentration of IgA in eluates when quantitated by fluoroimmunoassay were three- to five-fold higher in dermatitis herpetiformis skin biopsy specimens, than in eluates of bullous pemphigoid or normal skin biopsy specimens.

Linear IgA bullous dermatosis mimicking erythema multiforme in adult

This report describes a 49-year-old woman with an erythema multiforme--like rash and direct immunofluorescence showing linear IgA deposits at the dermoepidermal junction. Light microscopy revealed features of bullous pemphigoid, dermatitis herpetiformis, and erythema multiforme; immunoelectron microscopy demonstrated IgA deposition beneath the lamina densa about anchoring fibrils. These data provide additional information about the variable clinical and histologic manifestations of the adult linear IgA bullous dermatosis and emphasize the diagnostic dilemmas of light microscopy, which are resolved by immunohistochemical methods.

The pathogenesis of dermatitis herpetiformis: recent advances

Over the last two decades a rapid expansion of our knowledge regarding dermatitis herpetiformis has occurred, including the discovery of IgA in the skin, the discovery of an associated gluten-sensitive enteropathy, the noting of an increased prevalence of the human lymphocyte antigens (HLA)-B8 and -DRw3, and the documentation that the skin disease of many dermatitis herpetiformis patients can be controlled by a gluten-free diet. It has also been noted that two distinct forms of dermatitis herpetiformis occur, those with granular deposits of IgA at the dermoepidermal junction (85%-95% of dermatitis herpetiformis patients) and those with linear IgA deposits (10%-15% of dermatitis herpetiformis patients). These findings are reviewed with particular emphasis on the form of dermatitis herpetiformis associated with granular IgA deposits. The current findings regarding the nature and origin of the cutaneous IgA deposits, the role of the gluten-sensitive enteropathy, and the spectrum of both the immunologic and the nonimmunologic abnormalities associated with dermatitis herpetiformis are presented, and from these data pathophysiologic mechanisms are proposed that may be involved in dermatitis herpetiformis.

Dermatitis herpetiformis: extraction of intact IgA from granular deposits in dermal papillae

Dermatitis herpetiformis (DH) is characterized by the granular deposition of IgA in the dermal papillary tips. The source and antigenic specificity of this IgA are unknown, largely because of the previous inability to isolate it for study. These granular IgA deposits, pathognomonic of DH, have been specifically isolated from 4-mm punch biopsies. Specific isolation was achieved by removing contaminating serum IgA by a combination of washes in saline and sodium dodecyl sulfate without a reducing agent present and mechanical isolation of papillary dermis. The tissue IgA was then solubilized by a buffer containing 1% sodium dodecyl sulfate and 0.2 mM dithiothreitol, a reducing agent. Immunoreactive alpha chains were recovered in eluates of DH skin in 6-fold greater amounts than in eluates of normal skin, coincident with disappearance of immunofluorescent-staining granular deposits of IgA. Extracted specific IgA was recovered in sufficient quantity for detection by immunoenzymatic stain, was partially composed of a native (165 Kd) molecular mass, and had alpha and kappa staining material, all indicating that the extracted immunoglobulin was in part intact.

Dermatitis herpetiformis: 'pH optimum' for the release of potentially antigen-binding IgA fragments from papillary dermis of uninvolved skin by peptic digestion

In preparations of papillary dermis taken from clinically normal skin of patients with dermatitis herpetiformis (DH), the disappearance of granular IgA deposits induced by peptic digestion was partial at pH 4.5 and total at pH 4.1, as visualized by immunofluorescence microscopy. In a model system in which human monomeric IgA was digested by pepsin using a pepsin-IgA ratio of 100:0.3, an IgA concentration of 3 lambda g/ml and a pH range of 5.1-4.1, the degradation of IgA molecules did not appear to proceed beyond the formation of fragments corresponding to F (ab)'. When supernatants after peptic digestion of papillary dermis at pH 4.1 were analysed by sodium-dodecylsulphate (SDS)-polyacrylamide gel electrophoresis after reduction and alkylation followed by electrophoretic transfer to nitrocellulose membranes and subsequent immunochemical detection, IgA-like material corresponding to the alpha-chain part of F (ab)' fragments was found in preparations from DH patients but not in those from controls.