Monoclonal antibody 2B5 defines a truncated O-glycan, GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-6 (GalNAc), on mucins from deep gastric and duodenal glands as well as metaplasia and neoplasia of gastric differentiation.

Monoclonal antibody (MAb) 2B5 previously generated in BALB/c mice using gastric mucosa of the corpus as immunogen was characterized with regard to its binding epitope. Binding assays on structurally defined neoglycolipids from mucin glycans revealed that MAb 2B5 recognizes a carbohydrate epitope on a neutral O-glycan sequence from gastric mucins. This oligosaccharide chain has been characterized by mass spectrometry and methylation analysis and sequential exoglycosidase treatment of the derived neoglycolipid as GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-6OY (where 6OY corresponds to the GalNAc-ol fragment--O--(CH2)2 conjugated to dipalmitoylphosphatidylethanolamine). The selective binding of MAb 2B5 to mucus from deep gastric and duodenal glands, to gastric metaplasia or neoplasia with gastric differentiation may imply that mucin glycosylation in the respective cells is incomplete resulting in the accumulation of truncated blood group precursor chains. MAb 2B5 is the first monoclonal antibody which defines an epitope on M2-type antigens and may substitute, accordingly, for the inconvenient "paradoxical concanavalin A-horseradish peroxidase method" in histochemistry.