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.
Cy3 can be used to visualize the binding pattern of Narcissus pseudonarcissus Lectin (NPL/NPA) in cellular imaging and flow cytometry. Cy3 is more photostable than many other fluorophores and can be seen with TRITC filter sets. It is commonly combined with green-fluorescent dyes for dual-labeling.