Ultrastructural detection of lectin receptors by cytochemical affinity reaction using mannan-iron complex

A two-step affinity reaction is described for electron microscopic demonstration of the Concanavalin A as well as the Lens culinaris lectin receptors by means of the yeast mannan-iron complex. First the tissue was incubated in the lectin. Afterwards the incubation in the yeast mannan-iron complex was performed and reaction takes place between the still free second sugar binding site of membrane bound lectin molecules and the polysaccharides. This membrane receptor-lectin-polysaccharide complex is revealed by the electron dense iron core of the yeast mannan-iron complex. The specificity of the reactions could be demonstrated by addition of the hapten or by incubation in the yeast mannan-iron complex only. The proposed technique has proved useful for demonstration of lectin receptors in the small intestine.