How do antibodies help the immune system fight infection?

When the immune system encounters a virus, bacterium, or toxin, B cells can produce antibodies shaped to fit that target. Each antibody recognizes a particular antigen, like a lock and key, and can block the germ from entering cells or neutralize a toxin’s harmful action. Antibodies also tag invaders so other immune cells can destroy them more efficiently. The body can make different classes of antibodies, including IgG, IgA, IgM, IgE, and IgD, each with different jobs. Vaccines work in part by training the immune system to make these antibodies before a real infection occurs.