Describe how antibodies provide protection from diseases caused by viruses and bacteria

In the case of vaccines, we’re injected with antigens from a specific disease. Our body is able to make these antibodies as an immune response. This ensures that if we do get the disease, it will not likely be as serious because our bodies will already know how to fight it.

Viruses can also be removed from the body by antibodies before they get the chance to infect a cell. Antibodies are proteins that specifically recognise invading pathogens and bind (stick) to them. This binding serves many purposes in the eradication of the virus:

Firstly, the antibodies neutralise the virus, meaning that it is no longer capable of infecting the host cell.
Secondly, many antibodies can work together, causing virus particles to stick together in a process called agglutination. Agglutinated viruses make an easier target for immune cells than single viral particles.
A third mechanism used by antibodies to eradicate viruses, is the activation of phagocytes. A virus-bound antibody binds to receptors, called Fc receptors, on the surface of phagocytic cells and triggers a mechanism known as phagocytosis, by which the cell engulfs and destroys the virus.
Finally, antibodies can also activate the complement system, which opsonises and promotes phagocytosis of viruses. Complement can also damage the envelope (phospholipid bilayer) that is present on some types of virus

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