The immunohistochemical characterization of mucin peptide antigens and identification of blood group ABH- and Lewis-related carbohydrate antigens expressed in epithelium of normal human conjunctiva.Immunoperoxidase characterization of conjunctival glycoproteins was performed using antibodies against peptide and saccharide moieties of gastrointestinal mucins on conjunctival biopsy specimens from 89 healthy individuals of known ABO and Lewis red cell phenotypes.Ocular mucins had epitopes in common with the peptidic core of gastric mucin (M1 epitopes), but also contained sialylated saccharide chains like those of intestinal mucins. Anti-M1 gastric mucins, anti-type 1 precursor, and anti-T antibodies strongly stained the cytoplasm of goblet cells. Anti-Lea, anti-NeuAc-Lea, and anti-Leb antibodies stained both epithelial and goblet cells of Lewis-positive individuals only. Anti-H type 1, anti-H type 2, anti-A, and anti-B stained epithelial cells of ABH secretors. In addition, A-like epitopes independent of secretor phenotype were found in epithelial and goblet cells of all donors.The conjunctival mucins cross-react with antibodies specific for digestive mucins and for blood group-related carbohydrate epitopes. The distributions of Lewis and secretor phenotypes in conjunctiva are: 19% Lewis-positive nonsecretors, 71% Lewis-positive secretors, and 10% Lewis-negative secretors. Lea and Leb antigens are present on epithelial cells of Lewis-positive nonsecretors and Lewis-positive secretors, respectively, as expected for antigens under control of Lewis and secretor genes. The secretor alpha-2-fucosyltransferase is not expressed on goblet cells, as described for the goblet cells of the distal rectal colonic mucosae. ABH antigens synthesized by the products of A1, A2, B, and Se genes and modulated by the presence of the product of the Lewis gene are found in epithelial cells. In addition, A-related epitopes independent of the A1-A2 subtype, secretor, and Lewis phenotypes also are present in both epithelial and goblet cells.