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Understanding Immune Defenses: Phagocytosis, Antibodies, and Immunity Types

Explore the internal and external defenses of the immune system, including phagocytosis and the role of antibodies. Learn about different types of immunity and how they can protect the body from disease.

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Understanding Immune Defenses: Phagocytosis, Antibodies, and Immunity Types

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  1. Immunity A recap

  2. What protects the body from disease? What are the differences between internal and external defences? What are they?

  3. White blood cells PHAGOCYTE – neutrophils and monocytes Multi-lobed nuclei Produced in bone marrow LYMPHOCYTE – T and B Single nucleus Produced in bone marrow and matured in Thymus gland or Bone Marrow.

  4. Phagocytosis • This is a generalised immune response and results in large particles being engulfed and digested by phagocytes. • The phagocyte is attracted to the bacterium by proteins and chemicals that the bacteria itself releases. • It engulfs and then digests it.

  5. General or Specific • Phagocytosis is a fairly general reaction to the invasion of any pathogen. • This is a very useful ‘first’ defence but to be truly effective against disease we need to be able to have completely specific responses to specific antigens. • This is provided by antibodies

  6. Antibodies • Made from protein • Also known as immunoglobulins (Ig) • Synthesised by B-lymphocytes • They are entirely specific to one antigen (a bit like the active site of an enzyme)

  7. Structure • The constant region of the antibody remains the same in all. The variable region is antigen specific. • There are two binding sites on each antibody • They can change shape by moving at the hinge region

  8. How do they work? • Agglutination By sticking to more than one antigen the antibodies are able to make the pathogens clump together. This makes it possible for phagocytes to attack them. 2) Neutralisation Antibodies bind to the toxins released by the pathogen neutralising their effect.

  9. Self and Non-self • If antibodies recognised the body as non-self there would be a big problem. • In the developing foetus any antibody that is made that fits a ‘self’ marker is destroyed. As a result the only ones left are those suitable for pathogens.

  10. Immunity • There are different classes of immunity: ACTIVE PASSIVE And NATURAL ARTIFICIAL What do you think these are, how can you get them? (DON’T LOOK IN YOUR BOOKS!)

  11. Natural Immunity • Either inherited – eg from mother during pregnancy or through breast feeding • Or through actually getting the disease yourself

  12. Artificial Immunity • Result of deliberate exposure to the antigen – eg through vaccination

  13. Passive Immunity • Where antibodies are introduced to the body. This is shortlived as no memory cells are made.

  14. Active Immunity • Results in memory cells being formed – this is usually long-lasting.

  15. Vaccination • How does this work? • What are the risks? • What are the benefits? • If you were going to initiate a vaccination programme what considerations would you need to take?

  16. Different types of vaccine • Living attenuated micro-organism This is where the pathogen is injected but it is a weakened form. Eg measles, TB, polio • Dead micro-organism The pathogen is harmless but the antigens can induce immunity. Eg Typhoid, cholera, whooping cough • Genetically engineered micro-organism The antigen producing gene from the pathogen is transferred to a harmless bacterium. The body responds to the antigens without risk. Eg Hepatitis B

  17. Your task You are going to make a table summarising the 4 different types of immunity. Include what it is, how you get it and an example. Make sure you include plenty of detail, especially with the natural passive immunity in terms of it’s link with immunity for babies.

  18. Control of Disease • Vaccination controls infectious diseases. • For a population to gain immunity to a disease a certain percentage of the population needs to be immune – once that percentage is reached the population can benefit from herd immunity. • The percentage required will vary from disease to disease and from population to population. • However, it is not always as simple as that!

  19. Vaccination programmes You have been charged with the task of eliminating ‘skivalitis’, a highly contagious disease, from the population. What are you going to be looking for in your vaccine to ensure that you can immunise the entire population?

  20. You will need: • A suitable vaccine • Few side effects • Easy storage, delivery etc.. • People to administer the vaccine • The ability to administer the majority of the population.

  21. Your task • You need to draw a series of annotated diagrams to illustrate: • Phagocytosis • Antibody action • Humoural immunity • Cell-mediated immunity

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