Enterotoxigenic and verotoxigenic F18(+) Escherichia coli colonising the pig small intestine, adhere to receptors on intestinal villous enterocytes by F18 fimbriae. The aim of the present study was to define the F18R nature. The knowledge on the nature of this receptor could be important for the development of receptor-based treatments against F18(+) E. coli-induced disease. The adhesion of F18(+) E. coli to pig intestinal villous enterocytes was analysed in an in vitro assay. The adhesion of F18(+) E. coli but not of F4ac(+) E. coli was strongly inhibited by monoclonal antibodies (mAb) with blood group H-2 specificity. Conversely, blood group H-1 specific mAb could not inhibit the adhesion of F18(+) E. coli nor F4ac(+) E. coli. Moreover, the blood group H-2 trisaccharide strongly inhibited the adhesion of F18(+) E. coli, but only partially the adhesion of F4ac(+) E. coli. These data demonstrate that the F18 receptor contains the blood group antigen H-2 (alpha-fuc-(1-2)-beta-Gal-(1-4)-GlcNAc) as major carbohydrate. (C) 2004 Elsevier B.V. All rights reserved.