B6 - Preventing and treating disease

• Antigen


  Every cell has unique proteins on its surface called antigens. The antigens on the microorganisms that get into your body are different to the ones on your own cells.
• Antibody


  Your white blood cells make specific antibodies, which join up with the antigens and inactivate or destroy that particular pathogen.
• Bacterial diseases


  • Tetanus
  • Diphtheria
• Viral diseases


  • Polio
  • Measles
  • Mumps
• Vaccination


  1. Small amounts of dead or inactive forms of a pathogen are introduced into your body

  2. This stimulates the white blood cells to produce the antibodies needed to fight the pathogen and prevent you from getting ill

  3. If you meet the same, live pathogen, your white blood cells can respond rapidly and make the right antibodies just as if you had already had the disease, so that you are protected against it
• Vaccines have saved millions of lives around the world
• Smallpox has been completely wiped out by vaccinations
• Doctors hope polio will also disappear in the next few years
• Herd immunity


  If a large proportion of the population is immune to a disease, the spread of the pathogen in the population is very much reduced and the disease may even disappear
• Vaccination rates fall


  Herd immunity is lost and the disease can reappear
• In the 1970s in the UK, there was a scare about the safety of the whooping cough vaccine, vaccination rates fell from over 80% to around 30%, and thousands of children got whooping cough again and a substantial number died
• The World Health Organisation want 95% of children to have two doses of measles vaccine to give global herd immunity
• Currently, 85% of children get the first dose of measles vaccine and 56% get the second
• It will take money and determination to get global herd immunity against a range of different diseases, but the advantages both to individuals and to global economies are huge
• Painkillers


  Drugs such as aspirin and paracetamol that relieve symptoms but do not kill pathogens
• Antibiotics


  Medicines that can work inside your body to kill bacterial pathogens
• The impact of antibiotics on deaths from communicable diseases has been enormous
• Antibiotics first became widely available in the 1940s
• The introduction of antibiotics in the 1940s


  Had an enormous impact on deaths from maternal septicaemia
• Antibiotics cannot kill viral pathogens so they have no effect on diseases caused by viruses
• Strains of bacteria that are resistant to antibiotics are evolving
• There are some types of bacteria that are resistant to all known antibiotics
• The emergence of antibiotic-resistant strains of bacteria is a matter of great concern
• Unless scientists can discover new antibiotics soon, many millions of people in the future will die of bacterial diseases that we can currently cure
• Traditionally drugs were extracted from plants or microorganisms such as moulds
• In ancient Egypt mouldy bread was used on septic wounds, perhaps an early form of antibiotic
• 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
• Drugs traditionally extracted from

  • Plants
  • Microorganisms such as moulds
• Drugs extracted from plants

  • Digitalis
  • Digoxin
  • Aspirin
• Discovering penicillin


  1. Alexander Fleming growing bacteria

  2. Noticing mould killing bacteria

  3. Calling the substance 'penicillin'

  4. Unsuccessful attempts to extract active juice

  5. Ernst Chain and Howard Florey extracting penicillin

  6. Demonstrating penicillin could cure infections

  7. Producing penicillin on an industrial scale
• It is difficult to find chemicals that kill bacteria without damaging human cells
• Compounds showing promise as antibiotics


  • Noni fruit
• Only about 1% of soil microorganisms can be cultured in the lab
• Scientists have developed a special unit that enables them to grow microorganisms in the soil in a controlled way
• In 2015 they announced a completely new type of antibiotic from some soil bacteria that has destroyed all bacteria including MRSA and other antibiotic resistant pathogens
• Efficacy


  A good medicine must prevent or cure a disease or at least make you feel better
• Toxicity


  A good medicine must not be too poisonous or have unacceptable side effects for the patient
• Dosage


  A good medicine must be successfully taken into and removed from your body, reaching its target and being cleared from your system once it has done its work