Avidity progression of dietary antibodies in healthy and coeliac children

In most individuals minute amounts of food proteins pass undegraded across the intestinal mucosa and trigger antibody formation. Children with coeliac disease have enhanced antibody production against gliadin as well as other dietary antigens, e.g. beta-lactoglobulin, in cow's milk. Antibody avidity, i.e. the binding strength between antibody and antigen, often increases during antibody responses and may be related to the biological effectiveness of antibodies. The aim of the present study was to determine the avidity of serum IgG antibodies against beta-lactoglobulin and gliadin in healthy children during early childhood and compare these avidities to those found in children with coeliac disease. The average antibody avidity was analysed using a thiocyanate elution assay, whereas the antibody activity of the corresponding sera was assayed by ELISA. The avidity of serum IgG antibodies against beta-lactoglobulin as well as gliadin increased with age in healthy children, even in the face of falling antibody titres to the same antigens. Children with untreated coeliac disease had IgG anti-beta-lactoglobulin antibodies of significantly higher avidity than healthy children of the same age, and the same trend was observed for IgG antigliadin antibodies. The present data suggest that the avidities of antibodies against dietary antigens increase progressively during early childhood, and that this process seems to be accelerated during active coeliac disease.