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