Tumour-associated and differentiation antigens on the carbohydrate moieties of mucin-type glycoproteins.

In this report the carbohydrate antigens expressed on the three oligosaccharide domains, core, backbone and peripheral, of mucin-type glycoproteins are briefly reviewed in the light of recent observations with monoclonal antibodies. These have revealed that a number of cell-surface antigens which behave as tumour-associated and differentiation antigens of man or mouse are abundantly expressed on the carbohydrate chains of a variety of secreted mucins of human and animal origins and they belong to an antigen system which also includes the major blood group antigens. Examples are given of the use of well-characterized anti-carbohydrate antibodies to derive structural information on (a) mucin-type glycoproteins of human B lymphocyte membranes, (b) the high molecular weight glycoproteins of the normal human gastric and distal-colon mucosae and (c) tumour-derived glycoproteins from these two organs. Major differences between the antigenicities of the normal stomach and distal-colon, and between their tumour-derived glycoproteins, and the important effect of the secretor status in the expression of these antigens are described. These observations have enabled a better understanding of the individual and tissue differences in the expression of tumour-associated antigens. The possibility is raised that these carbohydrate structures (many of which also occur on certain N-linked oligosaccharides and glycolipids) are components of receptor systems for endogenous ligands. More tangible evidence is cited for the role of certain structures in this family of saccharides as receptors for infective agents.