Relation of antigenic structure of cereal proteins to their toxicity in coeliac patients

Unfractionated gliadin and its alpha-, beta-, gamma- and omega-gliadin subfractions were used as rabbit immunogens. The antisera were characterized by (1) Ouchterlony double diffusion, (2) binding of 125I-labelled gliadin subfractions, (3) inhibition by several gliadin subfractions of binding between gamma-gliadin antiserum and 125I-labelled gamma-gliadin. Double diffusion showed identical cross-reactivity between the antisera and the gliadin subfractions with the exception of omega-gliadin. Precipitin lines of partial identity with gliadin were observed against rye secalins and barley hordeins but not oat avenins or maize zeins. Binding was observed between unfractionated 125I-labelled alpha-, beta-, gamma- and omega-gliadins and all the antisera. There was binding of 125I-labelled omega-gliadin to the omega-gliadin antiserum but poor binding of 125I-labelled omega-gliadin to unfractionated alpha-, beta- and gamma-gliadin antisera. Competitive inhibition of binding between 125I-labelled gamma-gliadin and gamma-gliadin antiserum diluted 1:250 (v/v) demonstrated similar competition between alpha-, beta- and gamma-gliadins and this antiserum but poor competition between omega-gliadin, wheat glutenins, albumins and globulins, rye secalins, barley hordeins and oat avenins. These findings suggest that there is a good correlation between the antigenic structure of gliadin proteins and their toxicity to patients with coeliac disease.