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Labeled lectins with binding specificity to the hexose components of mucus glycoproteins (HPA, RCA I, PNA, Con A, WGA, and UEA I) were used to demonstrate structural differences in the glycoprotein composition of various cell types of the normal, benign and malignant gastrointestinal mucosa. While in the RCA I, UEA I, and WGA binding of normal mucus secreting cell types only quantitative differences were observed, the mucus in the surface epithelial cells of gastric mucosa and in the colonic goblet cells was characterized by the absence of PNA, Con A, and PNA, HPA binding sites, respectively. These lectins, however, showed a strong binding to the supranuclear, Golgi-region in the undifferentiated or activated forms of these cells. Even the staining intensity of the luminal membrane surfaces of the non mucinous parietal and chief cells was often stronger by PNA, HPA, and RCA I lectins than that of the mucus secretions in the highly differentiated mucus cells. These results indicate the existence of either heterogeneous glycoprotein components or mucus molecules with variations in the degree of glycosylation of their oligosaccharide chains in the different cells. The latter seems more likely since in benign and malignant alterations lectin binding sites appear in great density, which were found to be characteristic of the undifferentiated mucus cells or for the non mucinous cells of the normal gastric mucosa. Similarly in some gastric cancers which do not stain with the periodic acid-Schiff reaction at all, large amount of free or neuraminic acid substituted PNA binding sites can be detected.

A new source of agglutinins has been found in snails (albumin gland) and in many sorts of fish roe. These agglutinins do not only agglutinate red cells of various origin before and (or) after treatment with several enzymes (pronase, neuraminidase), but also different strains of bacterial microorganism. These reactions are not unspecific, but follow the rule of strong chemospecificity as could be demonstrated in several cases by haemagglutination inhibition and immunodiffusion tests, especially with the agglutinins from Helix snails, where artificially conjugated antigens were included, as well as a discussion of the nomenclature and topochemical arrangement of the receptors.

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