Invading microorganisms have antigens on their surface that the human body can recognise as being foreign - meaning not belonging to it.
When the body recognises a foreign antigen, lymphocytes (white blood cells) produce antibodies, which are complementary in shape to the antigen.
An antibody will only work on one type of microorganism because of this complementary nature.
Antibodies immobilise microorganisms by clumping them together.
Immobilisation of the microorganism reduces symptoms and prevents the spread of infection.
The clump of microorganisms is then destroyed by phagocytosis.
Phagocytosis is when a phagocyte (white blood cell) engulfs and digests the microorganisms.
Enzymes within the phagocyte digest the microorganism.