cross-reacting antigen

biology

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July 15, 2026

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The term "cross-reacting antigen" refers to antigens that share a common epitope, meaning they have a similar structural region. Because of this similarity, antibodies produced in response to one antigen can also bind to another antigen that possesses the same epitope.1

This phenomenon is significant in biology, particularly in the context of the immune system. For instance, it plays a role in autoimmune disorders. In some cases, an infection can trigger an immune response against a foreign antigen that is structurally similar to a self-antigen (a substance naturally present in the body). The antibodies generated to fight the infection may then mistakenly attack the body's own tissues, leading to damage. An example is rheumatic fever, where antibodies against certain streptococci can also react with heart muscle membranes.2

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immune system disorder
Cross-reaction with foreign antigens
…antigens are said to be cross-reactive. Autoantibodies stimulated by external antigens in this way can cause serious damage. For example, the streptococci that cause rheumatic fever make antigens that are cross-reactive with those on heart muscle membranes, and the antibodies that react with the bacteria also bind to the heart…
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…antigens are said to be cross-reactive. Autoantibodies stimulated by external antigens in this way can cause serious damage. For example, the streptococci that cause rheumatic fever make antigens that are cross-reactive with those on heart muscle membranes, and the antibodies that react with the bacteria also bind to the heart…
Read More