L’cross immunity describes a acquired immunity against an infectious agent that protects against another agent (virus or bacterium). Cross-immunity is linked to the phenomenon of cross reaction. In general, an antibody is specific for a antigen ; but sometimes antibodies bind to closely related antigens (they are said to be cross-reactive), because these antigens have epitopes common or have a similar structure.
Thus, there may be cross reactions with bacteria fromcash relatives. A bacterium has many antigens of surface. If an animal is immune to a bacteria by injecting whole bacteria, it produces antibodies against many bacterial antigens. If two bacteria have the same antigen, the animal immunized against one bacteria also produces antibody against the other bacteria.
Examples of cross immunity
The seasonal flu virus is known to mutate every year, but these variations are often minor. This explains why there may be some cross-immunity with viruses encountered in previous years.
More specifically, the influenza virus gate the proteins hemagglutinin (H) and neuraminidase (N). People who have been exposed to a virus carrying a certain type H may be partially protected against viruses of the same type. It is this phenomenon of cross-immunity which would explain that our sensitivity to influenza viruses is linked to our year of birth, as shown in a study published in 2016: people who have already encountered certain influenza viruses in their lifetime would be better protected than others against other influenza viruses.
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