Hemagglutinin (influenza)
Influenza hemagglutinin (HA) or haemagglutinin (British English) is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein. It is responsible for binding the virus to the cell that is being infected. HA proteins bind to cells with sialic acid on the membranes, such as cells in the upper respiratory tract or erythrocytes.
The name "hemagglutinin" comes from the protein's ability to cause red blood cells (erythrocytes) to clump together ("agglutinate") in vitro.
Read more about Hemagglutinin (influenza): Subtypes, Function and Mechanism, Structure, Neutralizing Antibodies