Immune system

2.6.4 Control of blood glucose

undefined Genetics

Immune system

  1. Pathogens

    1. Pathogens are microorganisms that cause infectious disease
    2. Bacteria & viruses can reproduce rapidly inside the body
    3. Bacteria can produce toxins that make people feel ill
    4. Viruses live & reproduce inside cells, causing damage

  2. White blood cells

    1. They engulf pathogens
    2. They produce antitoxins, which counteract the toxins produced by bacteria
    3. They produce antibodies, which are unique in destroying particular bacteria or viruses, providing immunity from that pathogen
    4. If a large proportion of a population is immune to a pathogen, the spread of the pathogen is greatly reduced, effecting “herd immunity”

  3. Treatment

    1. Vaccination

      1. People can be immunised against an infectious disease by introducing small quantities of dead or inactive forms of the pathogen into the body
      2. Vaccines stimulate the immune system to produce antibodies that destroy the pathogen
      3. This makes the person immune to future infections by the pathogen since the immune system can rapidly make the correct antibody, as if the person had previously had the disease
      4. The MMR vaccine is used to protect children against measles, mumps and rubella

    2. Medicine

      1. Some medicines, such as painkillers, help to relieve the symptoms of infectious disease, but do not destroy the pathogens
      2. Antibiotics, such as penicillin, are medicines that help cure bacterial disease by destroying infective bacteria inside the body
      3. It is important that specific bacterial diseases should be treated by specific antibodies
      4. The use of antibiotics has greatly reduced the number of deaths from infectious bacterial diseases
      5. Antibiotics cannot destroy viruses
      6. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues

  4. Antibiotic resistance

    1. Mechanism

      1. Mutations of pathogens produce new strains
      2. Antibiotics destroy individual bacteria of the non-resistant strain but resistant bacteria survive and reproduce, so the population of the resistant strain rises
      3. Antibiotics and vaccinations may no longer be effective against a new resistant strain of the bacteria
      4. The new strain will then spread rapidly because people are not immune to it and there is no effective treatment
      5. Many strains of bacteria, including MRSA1, have developed resistance to antibiotics
      6. Overuse and inappropriate use of antibiotics has increased the rate of development of antibiotic-resistant strains of bacteria

    2. Defence

      1. Antibiotics are not currently used to treat non-serious infections, such as mild throat infections, in order to slow the rate of development of resistant strains
      2. The development of antibiotic-resistant strains of bacteria necessitates the development of new antibiotics

    3. Cultures

      1. Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics
      2. For this, petri dishes and culture media must be sterilised before use to destroy unwanted microorganisms
      3. Inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame
      4. The lid of the petri dish should be secured with adhesive tape to prevent microorganisms from the air contaminating the culture, and stored upside-down to stop bacteria falling onto the agar surface
      5. In school & college laboratories, cultures should be incubated at a maximum temperature of 25 °C to greatly reduce the likelihood of the growth of pathogens that might be harmful to humans
      6. In industrial conditions, higher temperatures can produce more rapid growth
  1. Methisillin-resistant Staphylococcus aureus ↩