Localization of alpha-D-glucosyl and alpha-D-mannosyl groups of mucosubstances with concanavalin A and horseradish peroxidase.

Concanavalin A is a lectin which is known to bind specifically to alpha-D-glucosyl and alpha-D-mannosyl groups in the mucosubstances of mammalian tissues. The lectin molecule is bivalent; after its attachment to mucosubstances present in a histological specimen it can also bind horseradish peroxidase, a mannose-containing glycoprotein. The attached peroxidase may then be visualized by virtue of its histochemically demonstrable enzymatic activity. Other investigators have utilized this principle in the electron microscopic localization of cell-surface carbohydrates. A histochemical technique for light microscopy is described here, along with three control procedures which establish the specificity of the method. The technique is somewhat more sensitive than earlier ones in which fluorescent-labelled concanavalin A was used, and has the additional advantages that all the required reagents are commercially available and that sacilities for fluorescence microscopy are not needed.