Detection of inflammation- and neoplasia-associated alterations in human large intestine using plant/invertebrate lectins, galectin-1 and neoglycoproteins.

Commonly, plant and invertebrate lectins are accepted glycohistochemical tools for the analysis of normal and altered structures of glycans in histology and pathology. Mammalian lectins and neoglycoproteins are recent additions to this panel for the detection of lectin-reactive carbohydrate epitopes and glycoligand-binding sites. The binding profiles of these three types of probes were comparatively analyzed in normal, inflamed and neoplastic large intestine. In normal colonic mucosa the intracellular distribution of glycoconjugates and carbohydrate ligand-binding sites in enterocytes reveals a differential binding of lectins with different specificity and of neoglycoproteins to the Golgi apparatus, the rough and smooth endoplasmic reticulum and the apical cell surface. The accessible glycoligand-binding sites and the lectin-reactive carbohydrate epitopes detected by galectin-1 show the same pattern of intracellular location excluding the apical cell surface. Lectin-reactive carbohydrate epitopes detected by plant lectins of identical monosaccharide specificity as the endogenous lectin [Ricinus communis agglutinin-I (RCA-I), Viscum album agglutinin (VAA)], however, clearly differ with respect to their intracellular distribution. Maturation-associated differences and heterogeneity in glycohistochemical properties of epithelial cells and non-epithelial cells (macrophages, dendritic cells, lymphocytes) are found. Dissimilarities in the fine structural ligand recognition of lectins with nominal specificity to the same monosaccharide have been demonstrated for the galactoside-specific lectins RCA-I, VAA and galectin-1 as well as the N-acetylgalactosamine (GalNAc)-specific lectins Dolichos biflorus agglutinin (DBA), soybean agglutinin (SBA) and Helix pomatia agglutinin in normal mucosa and in acute appendicitis. Acute inflammation of the intestinal mucosa found in acute phlegmonous appendicitis is associated with selective changes of glycosylation of mucin in goblet cells mainly of lower and middle crypt segments resulting in an increase of DBA- and SBA-binding sites in the goblet cell population. Appendicitis causes no detectable alteration of neoglycoprotein binding. In contrast, tumorigenesis of colonic adenoma is characterized by increases in lectin-reactive galactose (Gal; Gal-beta1, 3-GalNAc), fucose and N-acetylglucosamine moieties and by enhanced presentation of respective carbohydrate ligand-binding capacity. This work reveals that endogenous lectins and neoglycoproteins are valuable glycohistochemical tools supplementing the well-known analytic capacities of plant lectins in the fields of gastrointestinal anatomy and gastroenteropathology.