Characterization of the mucosal immune response to dietary antigens in patients with dermatitis herpetiformis.
The association of dermatitis herpetiformis (DH) with granular IgA deposits at the dermal-epidermal junction and a gluten sensitive enteropathy (GSE) suggests that a mucosal immune response may play an important role in the pathogenesis of DH. The degree of antigenic restriction, the immunoglobulin class and subclass response to dietary antigens, and the relationship of antibodies against dietary antigens to IgA-containing circulating immune complexes (CIC) in patients with DH, however, are not known. We have examined the serum of 33 patients with DH for IgG and IgA antibodies against gliadin, and against 3 dietary proteins not thought to be related to GSE, beta-lactoglobulin (beta-lacto), bovine gamma globulin (BGG), and casein. Eleven of 33 (33%) patients with DH had IgA anti-gliadin antibodies, whereas IgA antibodies against beta-lacto were found in 11 of 33 patients (33%), against BGG in 15 of 32 (47%), and against casein in 6 of 33 (18%); 17 of 32 (53%) patients had IgA antibodies against one or more of these dietary antigens. Significantly higher levels of IgA antibodies were detected against beta-lacto (2,500 +/- 2,320 ng/ml, mean +/- SEM) and BGG (2,340 +/- 1,890 ng/ml) than gliadin (1,250 +/- 851 ng/ml) in this group of antibody positive patients (p less than 0.05, Wilcoxon signed ranks test). Eleven of 17 patients with IgA antibodies against dietary antigens were found to have IgA-containing CIC, whereas only one of the 15 antibody negative patients had IgA-containing CIC (p = 0.0008, Fisher's exact test). IgA anti-gliadin antibodies were found to contain both IgA1 and IgA2 with a significantly increased proportion of IgA2 when compared with the IgA2 composition of the total serum IgA (IgA2: anti-gliadin antibodies = 34 +/- 4.2%; total serum IgA = 19 +/- 4.8%, p = 0.02, Students paired t test). IgG antibodies against these antigens were found to occur slightly more frequently in amounts not significantly greater than IgA antibodies. This data demonstrates that a serum IgA and IgG antibody response to dietary antigens occurs in approximately 50% of DH patients with a higher proportion of IgA2 than total serum IgA and does not appear to be restricted to gliadin. This is significantly different from the pattern of cutaneous immunoreactants in patients with DH, and suggests that the deposition of IgA in DH skin may be the result of an atypical mucosal immune response, a non-immunologic interaction of IgA1 and DH skin, or arise from a non-mucosal source.
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