Résumé : The outer membrane protein (OMP) profiles from 8 Campylobacter jejuni and 5 Campylobacter coli fecal isolates grown under various conditions were compared by SDS-PAGE. The bacteria were grown under usual conditions, in iron-deficient medium (Dip) and on iron-supplemented medium (Fe). The OMP profiles of most bacterial strains grown under usual conditions, or in the Fe-supplemented medium, contained four major bands of approximately 31, 45, 63–66 and 97 kDa, and in addition, a number of minor bands. It was found that OMP from 10 of 13 strains tested and grown on iron deficient medium contained an intensive band of a protein in the molecular weight region of 76 kDa which was lacking in the OMP of bacteria grown in the presence of iron (iron-regulated protein). Sera from 11 children with C. jejuni infection analyzed by Western blot recognized the 76 kDa bands, in contrast to only one out of 10 control sera from healthy children. The Western-blot experiments demonstrated also various bands of other OMP components, both in OMP-Dip and OMP-Fe. The 45 kDa (porin protein) was recognized by all 11 serum samples from C. jejuni-infected patients and in 8 out of 10 control sera. The data suggested that the 76 kDa iron-regulated protein was expressed by bacteria during infection and it stimulated the immune response in children infected with C. jejuni. © 1994, Gustav Fischer Verlag, Stuttgart · Jena · New York. All rights reserved.