Gastrointestinal mucins. Structures and antigenicities of their carbohydrate chains in health and disease.

The carbohydrate chains of gastrointestinal mucins are of wide interest because the same structures occur on glycoproteins and glycolipids of cell membranes and they express a variety of antigens recognized by polyclonal and monoclonal antibodies. In this article we summarize the information available on the structures found in three domains ('peripheral', 'backbone' and 'core' regions) of the carbohydrate chains of mucins. We discuss the various antigens expressed on these domains and the changes in their expression in benign and malignant diseases of the gastrointestinal tract. These antigens include the major blood group antigens A, B, H, Lea and Leb, the Ii antigens and some hybridoma-defined antigens termed SSEA-1, VEP8/9 and FC 10.2, all of which are now regarded as differentiation antigens with changing expression during embryogenesis and stages of cell differentiation. The functions of these diverse carbohydrate chains have eluded us thus far; they deserve systematic investigation as possible receptors involved in cellular interactions and reactions with microbial agents.