Isotype distribution and serial levels of antibodies reactive with dietary protein antigens in dermatitis herpetiformis.

Using a sensitive enzyme-linked immunoassay (ELISA), a significantly increased prevalence (p less than 0.001) of serum antibodies reactive with wheat gliadin, bovine milk or ovalbumin has been demonstrated in 75% (33/44) of adult patients with dermatitis herpetiformis (DH), compared with healthy adults. There was no significant difference in the prevalence of antibodies (79%) in patients on a gluten-free diet or not on a gluten-free diet (72%). These serum antibodies reactive with gliadin, milk and ovalbumin were of the IgG isotype. However, IgA anti-gliadin antibodies were also detected in DH patients, but only in patients who were not on a gluten-free diet. In contrast, IgA anti-milk antibodies were also detected in DH patients irrespective of whether the patient was on a gluten-free diet. In DH patients, antibodies reactive with ovalbumin were often restricted to the IgG4 subclass and antibodies reactive with bovine milk antigens (notably casein) were distributed predominantly in both IgG2 and IgG4 subclasses, a similar IgG isotype distribution to that observed in healthy individuals. However, anti-gliadin antibodies in DH patients showed no predominant IgG4 subclass restriction. IgG4 anti-ovalbumin antibodies and IgG4 and/or IgG2 anti-casein antibodies persisted for up to 4 yr without fluctuation, irrespective of whether DH patients were on a gluten-free diet.