A fucose-containing epitope potentially involved in gamete interaction on the human zona pellucida

The oligosaccharide moiety of human, porcine and bovine zonae pellucidae was studied with lectins and monoclonal antibodies specific for tri- or tetra-saccharidic epitopes containing at least one terminal alpha-L-fucose. Animal eggs were collected from follicular aspirates, human eggs were collected from in-vitro fertilization and embryo transfer programmes and pooled into six groups. By direct immunofluorescence, the lectins reactivity was detected for the animal or the human zonae pools in the same way. Reactivity of Aleuria aurantia lectin demonstrated the presence of alpha-L-fucose terminal residues in the zonae from the three species studied. By indirect immunofluorescence, the 2-25 antibody reactivity was detected in every pool of human zonae whereas there was no evidence of any antibody reactivity on animal zonae. Using an anti-Lewis-b blood group antibody (2-25), we observed expression of this antigen as an intrinsic component of the human zona pellucida, independently of patients' Lewis red blood cell phenotypes. Antibody 2-25 inhibited the spermatozoa-zona binding in a hemizona assay, suggesting that this fucose-containing antigen could be part of a sperm-zona receptor.