Lectin

   Although "lectin" was originally coined to define agglutinins which could discriminate among types of red blood cells, today the term is used more generally and includes sugar-binding proteins from many sources regardless of their ability to agglutinate cells. Lectins have been found in plants, viruses, microorganisms and animals, but despite their ubiquity, their function in nature is unclear.   http://www.vectorlabs.com/Lectins/Ldescript.html