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Illustration showing influenza virus attaching to cell membrane via the surface protein hemagglutinin

In molecular biology, hemagglutinin or haemagglutinin (British English; both /ˌhɛməˈɡltɪnɪn/[1][2]) are glycoproteins which cause red blood cells (RBCs) to agglutinate or clump together. (Note that agglutination is one of three steps in the more complex process of coagulation.) The process of the RBC's agglutinating is called hemagglutination or haemagglutination.

Antibodies[3] and lectins[4] are commonly known hemagglutinins.


Examples include:

Uses in serology[edit]

Hemagglutination can be used to identify RBC surface antigens (with known antibodies) or to screen for antibodies (with RBCs with known surface antigens).

Using anti-A and anti-B antibodies that bind specifically to either the A or to the B blood group surface antigens on RBCs it is possible to test a small sample of blood and determine the ABO blood group (or blood type) of an individual.

The bedside card method of blood grouping relies on visual agglutination to determine an individual's blood group. The card has dried blood group antibody reagents fixed onto its surface and a drop of the individual's blood is placed on each area on the card. The presence or absence of visual agglutination enables a quick and convenient method of determining the ABO and Rhesus status of the individual.

Agglutination of red blood cells is used in the Coombs test.

See also[edit]


  1. ^ Robert S. Boyd - Knight Ridder Newspapers (May 24, 2007) [Oct 6, 2005]. "Scientists race to develop a vaccine against a killer flu". Mcclatchydc.com. Retrieved 2018-05-24.
  2. ^ "Bird flu: Don't fly into a panic - Harvard Health". Harvard.edu. Oct 2006. Retrieved 2018-05-24.
  3. ^ "hemagglutinin" at Dorland's Medical Dictionary
  4. ^ Hemagglutinins at the US National Library of Medicine Medical Subject Headings (MeSH)

External links[edit]