Narcissus pseudonarcissus lectin or agglutinin (NPL/NPA) is affinity purified composed of four subunits. It agglutinates rabbit erythrocytes but is non-reactive with human erythrocytes. NPA has an isoelectric point between pH 4.2 and pH 4.6 with a specific binding activity toward α-D-mannose, although studies have suggested that the purified lectin may have greater affinity for internal mannosyl residues than for nonreducing terminal units. A buffer washed column elutes the sugar α-methylmannoside.
Human studies have found NPA to be nearly non-mitogenic, but it has been reported through an in vitro study that mitogenicity of NPA is age-related, with lymphoproliferative response of peripheral blood mononuclear cells (PBMC) in umbilical cord blood has a sevenfold increase than adult blood. NPA has also been found to be mitogenic for PBMC from lambs and not adult sheep.
Narcissus pseudonarcissus Lectin (NPL/NPA) is conjugated to ferritin, that has a molecular weight of 474,000 g/mol (all 24 subunits combined). Ferritin-conjugated lectins can be used to visualize localization of specific saccharide moieties and examine the distribution of plasma membrane glycoproteins. These conjugates can be viewed via electron microscopy.