b3

• Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies
• If the same pathogen re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection

• Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body
• It is important that specific bacteria should be treated by specific antibiotics

They cannot:

• Antibiotics cannot kill viral pathogens
• Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens.
• It is difficult to develop drugs that kill viruses without also damaging the body’s tissues.

• Bacteria can mutate, sometimes the mutations can cause them to be resistant to an antibiotic. 
• If you have an infection, some of the bacteria might be resistant to antibiotics.
• This means that when the disease is treated, only the non-resistant strains of bacteria will be killed. 
• The individual resistant strain of bacteria will survive and reproduce, and the population of the resistant strain will increase. This is an example of natural selection.
• The resistant strain could cause a serious infection that can't be treated by antibiotics. [Eg. MRSA causes serious wound infections and is resistant to the powerful antibiotic meticillin]
• To slow down the rate of development of resistant strains, it's important for doctors to avoid over prescribing antibiotics. 
• It's also important that you finish the whole course of antibiotics and not just stop once you feel better.

Monoclonal antibodies are produced from a single clone of cells. The antibodies are specific to one binding site on one protein antigen and so are able to target a specific chemical or specific cells in the body.

• They are produced by stimulating mouse lymphocytes to make a particular antibody.
• The lymphocytes are fused with a tumour cell to make a cell called a hybridoma cell
• The hybridoma cell can both divide and make the antibody
• Single hybridoma cells are cloned to produce many identical cells that all produce the same antibody
• A large amount of the antibody can be collected and purified

Lymphocytes - produce antibodies but don't divide

Tumour cells - divides rapidly but doesn't produce antibodies

Hybridoma - makes antibodies and divides rapidly

• Different cells in the body have different antigens on their cell surface. Antigens are unqiue proteins on the surface of cells. You can make monoclonal antibodies that will bind to specific cells in the body.
• Cancer cells have antigens on their cell membranes that aren't found on normal body cells. They're called tumour makers.
• In the lab, you can make monoclonal antibodies that will bind to these tumour markers. An anti-cancer drugs can be attached to these monoclonal antibodies. This might be a radioactive substance, a toxic drug or a chemical which stops cancer cells from growing and dividing.
• The antibodies target specific cells because they only bind to the tumour markers.
• The drug kills the cancer cell but doesn't kill any normal body cells near the tumour.