Hemagglutinins refers to glycoproteins which bring about agglutination of erythrocytes or hemagglutination. Hemagglutination can be used to identify surface antigens on erythrocytes (with known antibodies) and, hence, the blood type of an individual. Hemagglutinins consist of lectins and antibodies. Lectins (from the Latin legere, to select) are non-immune glycoproteins that exhibit reversible binding to specific carbohydrate structures, glycans of glycoproteins, glycolipids and polysaccharides. Lectins own at least one non-catalytic domain, and, in some cases, a few carbohydrate binding...