A rapid, sensitive specific radioimmunoassay for alpha- and beta-gliadin has been developed using an antiserum raised in rabbits to A-gliadin, a component of alpha-gliadin. 2. The antigen used in the assay was alpha-gliadin labelled with 125I; antigen-antibody complexes were collected after adsorption to Staphylococcus aureus in suspension. 3. The sensitivity of the assay, as judged by competitive binding with unlabelled antigen, was 1 ng of alpha- or beta-gliadin, which show complete cross-reaction with this antiserum. 4. Cross-reactivity to other wheat proteins was less than 1% and no cross-reactivity to extracts of rye, barley or oats was observed. 5. This radioimmunoassay for alpha- and beta-gliadin has been used to measure their amount in different varieties of wheat flour, several foods prepared from flour, e.g. bread, biscuits and products prepared as 'gluten free'. The possibility of assaying for alpha-gliadin in prepared foods is of special value since alpha-, beta-, gamma- and omega-gliadin have been shown to exacerbate coeliac disease.
