Glycine-rich cell wall proteins act as specific antigen targets in autoimmune and food allergic disorders

Our objective was to investigate the presence of a B and T cell immune resp onse directed against the glycine-rich cell wall protein (GRP) in patients with different autoimmune disorders and with food allergy. GRP is an ubiqui tous food protein that has high homology with cytokeratins and other self p roteins [Epstein-Barr virus nuclear antigen-1 (EBNA-I), heterogeneous nucle ar ribonucleoprotein, fibrillar collagen] which are common targets in autoi mmune disorders. A peptide (GGYGDGGAHGGGYGG) derived from GRP was used to s creen human sera in direct and competitive ELISA assay. Anti-GRP-specific I gG were analyzed for their ability to cross-react with autoantigens. The in tracellular cytokine profiles of the peptide-specific T cell clones obtaine d from representative patients have been studied. BALB/c mice were immunize d with the peptide coupled to the carrier protein keyhole limpet hemocyanin (KLH), Serum IgG antibodies directed against the GRP peptide were detected in several autoimmune disorders and in food allergic patients, and were ab le to cross-react with autoantigens including keratin, collagen and EBNA-I, Twenty-five T cell clones showed a specific proliferative response to the GRP peptide and were of the T(h)0 phenotype, Eight of the 10 BALB/c mice im munized with the peptide coupled to KLH developed an autoimmune response. O ur data suggest that phylogenetically highly conserved epitopes in plants, viruses and humans may be responsible for an autoimmune response in suscept ible individuals. They also indicate that the antigen spreading of a partic ular sequence among apparently divergent proteins may participate to initia te or amplify an immune response.