Galanthus nivalis lectin (GNL) preferentially binds to structures containing (a-1,3) mannose residues, such as many viral glycoproteins, most notably the gp120 coat protein of HIV. Unlike most mannose-specific lectins, GNL is not a metalloprotein and does not require Ca++ or Mn++ for binding. Binding is preferentially directed toward structures containing (α-1,3) mannose residues. Also in contrast to most mannose-binding lectins, GNL will not bind α-linked glucose. GNL binds to rat and mouse IgM but not IgG. The only human serum protein reported to bind to this lectin is α2-macroglobulin.