Chapter 13- The Immune Response

13.1 The immune response

The white blood cells that produce antibodies are called lymphocytes, and they respond when pathogens enter the body. They identify the bacteria or virus, and release antibodies which stick on the surface
Antibodies stick to bacteria to immobilize them and act as a marker. The phagocytes can recognise them, then engulf and digest them
Natural immunity is when lymphocytes produce antibodies (after you are infected for the second time)
Scientists have developed vaccines in order to protect humans from diseases that can be fatal the first time you are infected (eg. smallpox, measles, polio)
All cells have surface proteins called antigens. Antigens on foreign cells trigger an immune response- why the body rejects donor tissue in transplants
Lymphocytes produce specific antibodies. If a pathogen is present, lymphocytes are stimulated to multiply, until there are sufficient numbers.
Whilst the cells multiply, you may experience symptoms. However, next time the antibodies are produced quickly, the lymphocytes develop immunological memory
A vaccine contains a dead or weak form of a pathogen. When they are injected, the lymphocyte releases antibodies, and develops its immunological memory. If you come into contact with the real form later, antibodies are quickly released to kill it

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This type of immunity is artificial immunity, as it results from a vaccine
Both natural and artificial immunity relies on the body quickly producing antibodies- it is active immunity
Sometimes, doctors inject antibodies into a patient with a dangerous infection- it is passive immunity
Vaccines can be prepared from dead pathogens (killed by chemicals/heat), parts of pathogens, using genes to produce a pathogen protein or culturing pathogens to select a safe strain (weakening)
The vaccine must be tested using tissue culture and animals to show that it stimulates antibody production without damaging tissue. When safe, it is tested on human volunteers
Doctors and nurses as encouraged to report any reactions once the mass vaccination starts, as it identifies rare side effects and possible faulty batches of vaccine

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