Monoclonal antibody FW6 defines an epitope on alpha 3/4-monofucosylated polylactosaminoglycans expressed by fetal and colon carcinoma-associated mucins.

A mouse IgM monoclonal antibody FW6 was established after immunization of mice with mucins from human amniotic fluid and was characterized with regard to its binding epitope. According to a series of biochemical criteria the epitope is located on O-linked neutral carbohydrates of M(r) 700,000 and M(r) 570,000 mucins in human amniotic fluid. The epitope is presumed to contain alpha 3/4-linked fucose and terminal beta 3/4-linked galactose that are labile to the fucosidase I from almond emulsion or to the galactosidase from bovine testes, respectively. Immunoreactive fractions of glycan alditols from human amniotic fluid mucins were partially characterized by fast atom bombardment-mass spectrometry and methylation analysis to be composed of monofucosylated polylactosamine-type deca- or nonasaccharides. According to antibody competition studies, inhibition assays with defined carbohydrates and binding assays on neoglycolipids monoclonal antibody FW6 are presumed to recognize a novel epitope that is distinct from known carbohydrate markers of the Lex/Ley family associated with colonic carcinomas. The selective reactivity of this monoclonal antibody to the majority of human colonic carcinomas and its nonreactivity to normal colonic mucosa may render this antibody as a valuable tool in cancer diagnosis or cancer treatment.