Lectin histochemistry of scrapie amyloid plaques

Peroxidase-labeled lectins were used for detection of specific monosaccharide residues in amyloid plaques in brains of scrapie-infected mice. The lectins tested recognize the following residues: beta-D-galactosyl (Ricinus communis agglutinin 120, RCA-1), alpha-D-galactosyl and alpha-D-galactopyranoside (Bandeirea simplicifolia aggl., BSA), alpha-D-mannosyl and alpha-D-glucosyl (Concanavalin A, Con A), N-acetylglucosaminyl and sialyl (Wheat germ aggl., WGA), sialoglycoconjugates (Limulus polyphemus aggl., LPA), alpha-L-fucosyl (Ulex europeus aggl., UEA-1 and Tetragonolobus aggl., TPA), N-acetyl-D-galactosaminyl (Helix pomatia aggl., HPA). The most intense staining reaction in amyloid plaques was observed with BSA and WGA; it was less intense with RCA-1, Con A, and HPA. This indicates that the plaque material contains glycoproteins with abundance of accessible residues of alpha- and beta-galactose, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine, and some types of sialo-glycoconjugates recognized by WGA. Such residues, like alpha-L-flucosyl recognized by UEA-1 and TPA, were almost undetectable in the examined plaques. There were also some differences in the staining intensity between small and large plaques (WGA and HPA) and between central and peripheral areas of the plaques. In the wall of micro-blood vessels relatively strong staining reaction was observed with RCA and BSA and less intense with WGA and Con A.