Lectin binding sites in the choroid plexus and choroid plexus papillomas.

The surface of the cells of the normal choroid plexus and of the plexus papillomas is coated by sialomucopolysaccharides, containing substances which are positively stained with the colloidal iron (Hale-) reaction. After pretreatment with neuraminidase sialic acid is removed rendering the membrane negative to the Hale reaction. Using FITC- or rhodamine-labelled PNA (Arachis hypogaea) and RCA (Rhicinus communis) lectins specific receptors are demonstrable. The identity of these distinct oligosaccharides containing receptors with the Thomsen-Friedenreich antigens suggests the possibility of an immunologic significance, e. g. in bacterial or viral infections of the brain. The application of histochemical techniques seem suitable to clarify the differential-diagnosis between choroid plexus papillomas on the one hand and metastasis of carcinoma and papillary ependymomas on the other hand.