12.7 PREVENTING AND TREATING DISEASE

Question 1

what is natural active immunity?

Answer 1

• immune system recognising antigens and forming antibodies, destroying the pathogen

Question 2

what is natural passive immunity?

Answer 2

• a new born baby cannot make antibodies initially, so antibodies cross the placenta from the mother to her foetus while the baby is in the uterus, so it has some immunity at birth
• first milk a mother makes is called colostrum, which is high in antibodies
• infant gut allows these glycoproteins to pass into the bloodstream without being digested

Question 3

what is artificial immunity?

Answer 3

• some diseases can kill people before their immune system makes the antibodies they need, so medical science can give immunity to pathogens without any contact to them live

Question 4

what is artificial passive immunity?

Answer 4

• antibodies are formed in one individual (often an animal), extracted and then injected into the bloodstream of another individual
• gives temporary immunity
• e.g. tetanus antibodies may be injected into those with tetanus providing temporary immunity from symptoms (cannot swallow or breathe), this can be life saving

Question 5

what is artificial active immunity?

Answer 5

• the immune system of the body is stimulated to make its own antibodies to a safe form of an antigen (vaccine), which is injected into the bloodstream (vaccination)
• not usually the live pathogen, as this could cause the disease and have fatalresults

Question 6

what is the first step in artificial active immunity?

Answer 6

1. pathogen is made safe in one of a number of ways so that the antigens are intact but there is no risk of infection, vaccines may contain:
   - killed or inactivated bacteria and viruses e.g. whooping cough
   - attenuated (weakened) strains of live bacteria or viruses e.g. rubella
   - toxic molecules that have been altered and detoxified e.g. tetanus
   - isolated antigens extracted from the pathogen e.g. influenza vaccine
   - genetically engineered antigens e.g. hepatitis B vaccine

Question 7

what are the following steps of artificial active immunity?

Answer 7

2. small amounts of safe antigen (vaccine) are injected into the blood
3. primary immune response is triggered by the foreign antigens and your body produces antibodies and memory cells as if you were infected with a live pathogen
4. if you come into contact with a live pathogen, secondary immune response is triggered and you destroy pathogen rapidly before you suffer symptoms of the disease

Question 8

what is an epidemic?

Answer 8

• when a communicable disease spreads rapidly to a lot of people at a local or national level

Question 9

what is a pandemic?

Answer 9

• when the same disease spreads rapidly across a number or countries and continents

Question 10

what is herd immunity?

Answer 10

• when a significant number of people in the population have been vaccinated, this gives protection to those who do not have immunity
• now there is minimal opportunity for an outbreak to occur

Question 11

what are two examples of communicable diseases that cause problems at a global level and cannot be prevented by vaccination yet?

Answer 11

• malaria (evasive, spends time inside erythrocytes so its protected by self antigens)
• HIV (enters macrophages and T helper cells, disabling immune system)

Question 12

what is penecillin?

Answer 12

• first widely used, effective, safe antibiotic capable of curing bacterial diseases
• discovered by Alexander Fleming, when he found it growing on his staphylococcus cultures

Question 13

what are some common medicinal drugs, apart from penecillin?

Answer 13

• docetaxel/ paclitaxel
• aspirin
• prialt
• vancomycin
• digoxin

Question 14

what is the source of docetaxel/ paclitaxel and what does it do?

Answer 14

• derived originally from yew trees
• treatment of breast cancer

Question 15

what is the source of aspirin and what does it do?

Answer 15

• AKA acetylsalicylic acid
• based on compounds from sallow (willow) bark
• painkiller, anti-coagulant, ant-pyretic (reduces fever), and anti-inflammatory

Question 16

what is the source of prialt and what does it do?

Answer 16

• derived from venom of a cone snail from oceans around Australia
• new pain-killing drug 1000 times more effective than morphine

Question 17

what is the source of vancomycin and what does it do?

Answer 17

• derived from a soil fungus
• powerful antibiotic

Question 18

what is the source of digoxin and what does it do?

Answer 18

• based on digitoxin, originally extracted from foxgloves
• powerful heart drug used to treat atrial fibrillation and heart failure

Question 19

what are pharmacogenetics?

Answer 19

• the science of interweaving knowledge of drug actions and personal genetic material (personalised medicine)

Question 20

what is synthetic biology?

Answer 20

• using the techniques of genetic engineering, so we can develop populations of bacteria to produce much needed drugs that would otherwise be too rare, expensive or not available
• strand of this is nanotechnology, where tiny non-natural particles are used for biological purposes e.g. to deliver drugs to specific sites within the cells of pathogens or tumours

Question 21

what is selective toxicity?

Answer 21

• antibiotics interfere with the metabolism of the bacteria without affecting the metabolism of human cells
• antibiotics and becoming less effective in treatment of bacterial diseases as bacteria are becoming more resistant

Question 22

how have bacteria developed antibiotic resistance?

Answer 22

• if a random mutation during bacterial reproduction produces a bacterium that is not affected by an antibiotic, that is the one best fitted to survive and reproduce, passing on the antibiotic resistance mutation to the daughter cells
• bacteria reproduce very rapidly, so once a mutation occurs it does not take long to grow a big population of antibiotic-resistant bacteria

Question 23

what are two examples of antibiotic-resistant bacteria?

Answer 23

• MRSA (methicillin-resistant Staphylococcus aureus)
• Clostridium difficile (C. difficile)

Question 24

what is MRSA?

Answer 24

• bacterium carried by up to 30% of the population on their skin or in their nose
• in the body it causes boils, abscesses and potentially fatal septicaemia
• was treated effectively with methicillin, but mutation has produced methicillin-resistant strains

Question 25

what is C. difficile?

Answer 25

• bacterium in the guts of about 5% of the population
• produces toxins that damage the lining of the intestines, leading to diarrhoea, bleeding and even death
• not a problem for a healthy person but when commonly-used antibiotics kill off much of the ‘helpful’ gut bacteria it survives, reproduces and takes hold rapidly

Question 26

how can antibiotic resistant infection be reduced in the long term?

Answer 26

• minimising use of antibiotics, and completing every course of antibiotics to reduce risk of resistant individuals surviving and developing into a resistant strain population
• good hygiene in hospitals, care homes and in general, has a major impact on the spread of all infections, incl. antibiotic resistant strains