Chapter 6: Preventing and treating disease

Question 1

Vaccination

Answer 1

• If a pathogen enters the body the immune system tries to destroy it
• Vaccination involves introducing small amounts of dead or inactive forms of a pathogen into your body to stimulate the white blood cells (lymphocytes) to produce antibodies. If the same live pathogen re-enters the body, the white blood cells respond quickly to produce thousands of correct antibodies, preventing infection. These antibodies stay in the blood in case the same pathogen comes back again, meaning you are immune to that pathogen
• If a large proportion if the population is immune to a pathogen, the spread of the pathogen is much reduced

Question 2

Antibiotics and painkillers

Answer 2

• Painkillers and other medicines treat the symptoms of disease but do not kill the pathogens that cause it
• Antibiotics cure bacterial disease by killing the bacterial pathogens inside your body
• The use of antibiotics has greatly reduced deaths from infectious diseases
• The emergence of strains of bacteria resistant to antibiotics is a matter of great concern
• Antibiotics do not destroy viruses because viruses reproduce inside the cells. It is difficult to develop drugs that can destroy viruses without damaging your body cells

Question 3

Discovering drugs

Answer 3

• Traditionally drugs were extracted from plants, for example. Digitalis, or from microorganisms, for example, penicillin
• Penicillin was discovered by Alexander Fleming from the penicillium mould
• Most new drugs are synthesised by chemists in the pharmaceutical industry. However, the starting point may still be the chemical extracted from a plant

Question 4

Developing drugs

Answer 4

• New medical drugs are extensively tested for efficacy, toxicity and dosage
• New drugs are tested in the lab using cells, tissues and live animals
• Preclinical testing of new drugs takes place in the lab on cells, tissues and live animals. Clinical trials use healthy volunteers and patients. Low doses are used to test for safety, followed by higher doses to test for optimum dose
• In double blind trials, some patients are given a placebo

Question 5

Making monoclonal antibodies

Answer 5

• Monoclonal antibodies are produced from a single clone of cells. Each type is specific to one binding site on a specific protein antigen, so they can target specific cells in the body or specific chemicals
• Monoclonal antibodies are produced by stimulating mouse lymphocytes to make a specific antibody. Large amounts of the specific monoclonal antibody can be collected and purified.

• Monoclonal antibodies are used for:
o For diagnosis in pregnancy tests – these rely on the monoclonal antibodies that bind with the hormone human chorionic gonadotropin (HCG) that is made in the early stage of pregnancy. If the antibodies in the test detect the hormone in the urine it will show a positive result

  o	In labs to measure levels of hormones and other chemicals in the blood to detect pathogens for research

  o	To identify or locate specific molecules in cells or tissue

Question 6

Use of monoclonal antibodies

Answer 6

• Monoclonal antibodies are used in the treatment of disease
• They have been developed against the antigens on cancer cells
• If the monoclonal antibody is bound to a radioactive substance, a toxic drug, or a chemical that stops cells growing or dividing, it will deliver the substances to the cancer cells without harming other cells in the body
• Monoclonal antibodies have created more side effects than expected and are not yet as widely used as hoped when they were first developed