An antibody is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody recognizes a specific antigen unique to its target. This is because at the two tips of its "Y", it has structures akin to locks. Every lock only has one key, in this case, its own antigen. When the key is inserted into the lock, the antibody attaches, tagging the microbe or an infected cell for attack by other parts of the immune system or by directly neutralizing its target (i.e. blocking a part of the microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.
