How do antibodies help to fight infections?

Antibody tests can detect the presence of antibodies in the blood that

Antibodies, also known as immunoglobulins (Ig), are specialized proteins that bind to a uniquely shaped object—called an antigen—that is found on the surface of a pathogen. These pathogens can be things such as bacteria or viruses.

with a fitted molecular shape—and then either destroys the pathogen or tags it so other immune cells will recognize it.

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