Arachis hypogaea agglutinin (PNA) is purified by fractionation and is consisting of four subunits of approximately 27,000 each. This lectin has an isoelectric point between pH 5.5 and pH 6.5. It has a carbohydrate specificity for GalÎ²3GalNAc with an eluting sugar of galactose. Galactose and lactose are poor inhibitors while disaccharide Gal Î²(1->3)GalNAc and desialylated human erythrocyte N-substance (T-antigen which is present in many M and N blood groups) are potent inhibitors of PNA.Although extracts of Arachis hypogaea do not agglutinate untreated or trypsin-treated human erythrocytes, PNA has been known to agglutinate neuraminidase-treated human red blood cells. PNA may be used for clinical determination of T-polyagglutinability of erythrocytes and probing cell membranes of normal and malignant cells. This lectin can be of use in characterization of tumor-specific antigens on the surface of malignant cells. It can be employed in the fractionation of stem cells in mice for use in bone marrow transplantation across histocompatibility barriers.