Unit 3 immunology

• What is a pathogen?

  A disease causing organism, such as bacteria, viruses or fungi.
• What is an example of physical barriers against pathogens?

  Skin - prevents pathogens from entering the body.

  Nose hair - traps the pathogen before it can enter the lungs.

  Cilia - lines the trachea and moves pathogens and mucus towards the throat to be swallowed into the stomach to be destroyed.
• What are the role of goblet cells?

  They produce mucus to trap pathogens.
• What are some examples of chemical barriers against pathogens?


  Stomach acid - pH of 1-3 to kill pathogens that have been consumed in food or drinks.

  Tears and saliva - contains enzymes (lysosymes) that destroys bacterial cells by breaking down their cell walls.

  Mucus - sticky substance in the trachea to move pathogens away from the lungs.
• What is the inflammatory response?

  A localised defence mechanism used by the body following an injury or infection.
• What are the stages of the inflammatory response?

  Injury occurs.

  Mast cells release histamine, resulting in vasodilation of capillaries to increase permability.

  Increased blood flow.

  Phagocytes and clotting elements accumulate to form a scab to reinforce the physical barrier.
• What is a lymphocyte?

  A white blood cell involved in the specific immune system. They recognise antigens on pathogens.
• What are B lymphocytes responsible for?

  Producing antibodies against antigens which leads to the destruction of the pathogen.
• What are B lymphocytes associated with?

  B lymphocytes can trigger a hypersensitive reaction to a harmless antigen such as pollen. This is known as an allergic reaction.
• What are T lymphocytes responsible for?

  To destroy body cells that have been infected by a pathogen. They recognise antigens of the pathogen and induce apoptosis.
• What are T lymphocytes associated with?

  Autoimmune disease, T lymphocytes can fail to recognise the difference between self-antigens and non-self antigens resulting in the T lymphocytes attacking its own cells.
• What is 2 examples of autoimmune diseases?

  Rheumatoid arthritis, type 1 diabetes.
• What is apoptosis?

  Programmed cell death after being infected by a pathogen.
• What is phagocytosis?

  When a phagocyte engulfs a pathogen to destroy it.
• What are the stages of phagocytosis?

  The pathogen invades the immune system.

  Phagocytes recognise the pathogen.

  The pathogen then englufs the pathogen in a vacuole.

  The cell then uses digestive enzymes within lysosomes to destroy the pathogen.

  Cytokines attract more phagocytes to the site of infection.
• What are cytokines?

  Small chemical signaling molecules that attract more phagocytes and other white blood cells to the site of infection.
• What are memory cells and how are they useful in the immune system?

  After an infection some lymphocytes remain in the immune system. If the same pathogen enters the immune system again the response is quicker and efficient.
• What is an antigen?

  A protein marker on the surface of all cells to tell the immune system which cells are self-cells and which cells are foreign cells.
• What are natural killer cells?

  They induce the pathogen or infected cell to produce self destructive enzymes to induce apoptosis.
• What are the characteristics of an antibody?

  Globular Y shaped and binding sites which attach to antigens to immobilise the antigen.
• What cell produces antibodies?

  B lymphocytes.
• Where are B and T lymphocytes produced and where do they mature?

  B and T lymphocytes are produced in bone marrow.

  T lymphocytes mature in the thymus.

  B lymphocytes mature in bone marrow.
• What is HIV?

  Human immunodeficiency virus (HIV) is a virus that attacks and destroys the bodys T lymphocytes. This can result in the development of Acquired Immune Deficiency Syndrome (AIDS).
• Why are individuals with AIDS vulnerable to infections?

  AIDS results in a weakened immune system making them more vulnerable to secondary infections.
• What is naturally acquired immunity?

  An individual is exposed to the disease and makes antibodies. Memory cells stay in the immune system and if a secondary infection occurs, it is fought off often with no symptoms (example - chicken pox).
• What is artificial acquired immunity?

  An individual receives a small dose of a vaccine containing antigens which have been treated to make them non-infectious. The body makes antibodies but no disease is caused (example - polio).
• What is naturally occurring passive immunity?

  Antibodies from the placenta from mother to foetus (or from breast milk to baby) giving the child protection for a short period of time until its own immune system develops.
• What is artificially occurring passive immunity?


  Antibodies are made artificially. The antibodies will provide some immunity but will not last for long. Used in cases of snake bites where antibodies neutralise the snake venom.
• Give an example of a bacteria causing pathogen.


  Salmonella.
• Give an example of a virus causing pathogen.

  HIV (human immunodeficiency virus).
• How can quarantine prevent the transmission of infectious diseases?

  This allows isolation of a pathogen, therefore the disease is unable to spread.
• How can antisepsis prevent the transmission of infectious diseases?

  Antisepsis slows down the growth of microorganisms that exist on living tissue, therefore reducing the chances of infection.
• How can individual responsibility prevent the transmission of infectious diseases?

  This includes good hygiene, care in sexual health and appropriate handling/storage of food.
• How can control of vectors prevent the transmission of infectious diseases?


  This involves controlling other organisms which carry disease.

  Example - pesticides used to control mosquito populations which carries malaria.
• How do vaccines work to prevent infection?

  Vaccines mimic the natural secondary response to an infection by creating memory cells.
• What 4 types of pathogens can be used in a vaccine?

  A dead pathogen, a weakened pathogen, part of a pathogen and an inactive pathogen.
• What is herd immunity?

  When a majority of the population are vaccinated to prevent the spread of a disease.
• What is antigenic variation?

  Our memory immune response is no longer effective/less effective.

  Vaccines need to be updated with latest variants to ensure protection.
• What is antigenic drift?

  Small changes in the antigens that occur by mutation in the virus over time. Researchers can predict variants and include these in our annual vaccines.
• What is antigenic shift?

  Large changes that occur due to recombination and can lead to pandemics. These changes are hard to predict, making vaccination programmes difficult to plan.