Antigenic variation
Antigenic Variation
Antigenic variation (/ænˌtɪdʒəˈnɪk ˌvɛəriˈeɪʃən/) is a mechanism that pathogens use to evade the host's immune response. The term is derived from the words 'antigen', which refers to a substance that induces an immune response, and 'variation', which means change or difference.
Definition
Antigenic variation refers to the process by which an infectious agent such as a virus or bacteria alters its surface proteins in order to evade a host immune response. This allows the pathogen to persist within the host and can lead to chronic or recurrent infections.
Mechanism
The mechanism of antigenic variation involves changes in the genes that encode for the pathogen's surface proteins. These changes can occur through several processes, including genetic recombination, mutation, and gene conversion. The result is a diverse population of pathogens within a single host, each expressing a different set of surface proteins.
Examples
One of the most well-known examples of antigenic variation is seen in the Influenza virus, which undergoes frequent changes in its surface proteins, hemagglutinin (H) and neuraminidase (N). This is why new strains of the flu virus emerge every year, necessitating annual updates to the flu vaccine.
Another example is the Trypanosoma brucei, a parasite that causes African sleeping sickness. This parasite can switch the expression of its surface glycoproteins, allowing it to evade the host's immune response and establish a long-term infection.
Clinical Significance
Understanding antigenic variation is crucial for the development of effective vaccines and therapies. By studying how pathogens change their surface proteins, scientists can design strategies to prevent or treat infections.
See Also
External links
- Medical encyclopedia article on Antigenic variation
- Wikipedia's article - Antigenic variation
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