Affinity purified Vicia villosa lectin or agglutinin (VVL/VVA) is a tetramer composed of four subunits. VVL consists of A and B subunits, with a dominant isolectin that appears to be B subunit-rich. A4 isolectin agglutinates specifically A1 erythrocytes. B4 isolectin does not agglutinate A, B, or O-erythrocytes; however, B4 binds the Tn antigen, a molecule expressed on the surface of most tumor cells. A2B2 and similar tetramer isolectins display properties characteristic of both A4 and B4 isolections.Cy5, when bound to Vicia villosa Lectin (VVL/VVA), can show the binding pattern of this lectin in cellular imaging and flow cytometry. The excitation wavelength required for Cy5 to fluoresce is high enough to avoid overlap with most other fluorochromes, making it useful for dual-labeling experiments. Because of this high excitation, there is typically less background from autofluorescence of biological specimens.