🦠microbiology review

Hemagglutinin

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Hemagglutinin is a glycoprotein found on the surface of certain viruses, such as the influenza virus, that causes red blood cells to clump together. It plays a crucial role in the initial stages of viral infection by binding to host cell receptors.

5 Must Know Facts For Your Next Test

  1. Hemagglutinin facilitates the entry of the virus into host cells by binding to sialic acid-containing receptors.
  2. It is one of the main antigens targeted by the immune system during an influenza infection.
  3. Hemagglutinin undergoes frequent mutations, leading to antigenic drift and making it challenging for vaccines to provide long-term protection.
  4. The effectiveness of hemagglutination assays relies on this glycoprotein's ability to agglutinate red blood cells.
  5. Different subtypes of hemagglutinin are designated by numbers (e.g., H1, H3) and are used in naming influenza strains (e.g., H1N1).

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