Lack of cross-reactivity between casein and gliadin in sera from coeliac disease patients

Background: While searching for antigliadin and anticasein antibodies in sera from coeliac patients we investigated more than 20 persons suffering from this enteropathy, In some of sera, we registered antibodies against gliadin and in parallel the appearance of anticasein antibodies. A high percentage of glutamic acid has been proven by amino acid analysis in both these proteins, Therefore we try to demonstrate the existence of cross-reactivity between them in sera from coeliac patients. Methods: We analyzed sera from 5 adult patients by using Western blot (SDS-PAGE and immunoblot assay). All of them had previously proven serum antibodies against casein and gliadin, In the procedure, antigliadin-antibodies were removed from sera by adsorption with gliadin. Adsorbed antibodies were then eluted from the adsorbent. Results: Adsorbed samples retained anti casein activity. Eluates had a strong reactivity to gliadin but not to casein. Conclusion: No cross-reactivity restricted to any of the immunoglobulin isotypes (IgG, IgM, IgA) had been proven between these two proteins. Before the final conclusion, we believe the study has to be completed by using partly of totally disassembled proteins by intestinal enzymes. It might be that enzymatic digestion could open some epitopes shared by both these proteins.