Sub‐class of IgG in allergic disease I. IgG sub‐class antibodies in immediate and non‐immediate food allergy

Abstract

Abstract. Previous studies have suggested that, apart from IgE‐mediated reactions, some of the symptoms of food allergy may be caused by IgG antibodies to food proteins. This study was carried out to see if there were any distinctive features of the IgG sub‐class antibody response to dietary antigens which occurs in food allergic patients. IgG subclass antibodies were measured using a quantitative enzyme‐linked immuno‐sorbent assay (ELISA) to wheat gliadin, ovalbumin and bovine casein in twenty patients who had coeliac disease and in twenty‐eight egg allergic patients. These were compared with twenty‐one atopic dermatitis patients who did not have food allergy and twenty‐six healthy control subjects. Coeliac disease patients tended to have raised IgG antibody levels (especially IgG1) to all three antigens but these overlapped considerably with that seen in egg allergic and atopic dermatitis patients. Coeliacs who avoided gluten had anti‐gliadin antibody levels which did not differ from those seen in healthy subjects but nevertheless had raised anti‐ovalbumin and casein‐specific antibodies. The IgG antibody was largely restricted to IgG1 and IgG4 sub‐class although the relative amount of each varied with the antigen. Although gliadin‐specific antibodies were mainly IgG1, ovalbumin‐specific antibodies were mainly IgG4. The increased antibody levels to all three antigens in coeliacs were caused by a raised IgG1 response, IgG4 antibodies were usually normal. Egg allergic patients also had raised IgG1 but not IgG4 antibodies to ovalbumin. These data show that the response to different dietary antigens can vary with the antigen. The fact that IgG1 and not IgG4antibodies were raised to all three antigens in patients with coeliac disease suggests that they are a secondary consequence of the disease, perhaps reflecting increased transport of antigens across a damaged gut mucosa rather than a specific immunopathological reaction. However, the observation that antibodies to gliadin, and not ovalbumin or casein, fell following gluten avoidance shows that the response to gliadin, at least, is dependent upon continued exposure to antigen.

Gliadin IgG Subclass Antibodies in Patients with Coeliac Disease

“…We detected only IgG2, 3 or 4 antibodies directed against either gliadin or ca sein in a minority of the subjects studied, although those few subjects who gave positive results tended to be in the untreated coeliac patient group. While an other group has occasionally observed high IgG4 an tibody titres to casein [10] in specific asymptomatic healthy controls, cross-checking of the values ob tained has confirmed that there is a wide variation of titres to this dietary antigen in normal controls. Thus we have not found a different IgG subclass antibody profile between gliadin and casein, a dietary control antigen, in the untreated coeliac patients.…”

Influence of the G2m(n) allotype and age on IgG subclass distribution in antibodies to dietary proteins in children with coeliac disease

“…According to this, adult patients should have higher shares of IgG2 AGA, and IgG4 ALA and AOA than children. In a study comprising 20 samples of adult coeliac patients, IgGl was found to predominate AGA; IgG2 was found in only a few patients and in small amounts (Kemeny et al, 1986). In another study, of patients with irritable bowel syndrome or bronchial asthma and healthy subjects, IgGl, IgG2 or IgG4 dominated in AGA among individuals (Barnes et al, 1988).…”

The functional affinities of antibodies of different IgG subclasses to dietary antigens in mothers and their babies

“…In previous studies of the early immune response to dietary antigens we have shown that IgG antibody responses to casein and ovalbumin during the first year of life are predominantly in the IgG I subclass, whilst those seen in adults are biased to IgG4 [13,16]. In this study we have examined the titre and functional affinities of IgG I and IgG4 antibodies to ovalbumin and casein in infants, from this same study [16], at 1 year of age, and their mothers.…”

“…Studies in experimental animals have demonstrated that the outcome of oral immunization is diverse, depending on many factors including the form of antigen [13] and the age and previous antigenic experience of the recipient [14]. In addition, the presence of passively transferred maternal antibodies may influence the subsequent immune responses of offspring [14,15] …”