Rumours (or previously known as Chinese whispers).. What does this show?

1. Rumours (or previously known as Chinese whispers)..What does this show?

2. Aim of this lesson is to Answer these questions1. Why is there a new vaccine for the flu every year?2. Is there any way to evade the immune system?

3. What do you notice here?

4. Mutations in the nucleic acid which can eventually lead to the altering of the surface markers (antigen) New antigen So new Vaccine needed Called Antigenic variation What is a mutation again? Antigenic variation

5. A mutation is a change in the DNA sequence Mutations can occur through; copying errors -exposure to mutagens (like UV light, ionising radiation, chemicals or certain viruses) http://nature.ca/genome/04/0413_e.cfm#010

6. Pairs please .... • Bacteria, viruses and protozoa all have the ability to undergone antigenic variation. • MODEL IT USING PLASTICINE/PIPE CLEANERS ETC. • Partner up; • one of you find out about trypansomiasis (p341) • ONE OF YOU FIND OUT ABOUT MALARIA (P342)

7. DIRECT ATTACK ON THE IMMUNE SYSTEM • The immune system can be hijacked; • Tb (mycobacterium tuberculosis) hides inside the phagocytes • Hiv (human immunodeficiency virus) hides inside t helper cells ( t lymphocytes) • HOT QUESTION – what are the problems with hiding in t helper cells? (function of T helper cells are to .....)

8. hiv • Retrovirus – with rna not dna • Glycoprotein receptors help it bind to t lymphocytes

9. hiv • Uses protein synthesis of cell to reproduce • Leaves through budding

10. Hiv avoidance • B cells do make antibodies, however ineffective as hiv “hides” in helper T cells. • T helper cells needed in activation of the rest of the immune system, so down regulate immune system • Thus opportunistic infections can become major problem • Down regulation stage know as aids – acquired immunodeficiency.

11. Translate the writing into pictures • Immune system is like .... • HIV is like ..... • tb is like .....

12. Put these cards into ordernow come up with a series for tb Demonstrate your understanding

13. Review – can you answer these? 1. Why is there a new vaccine for the flu every year?2. Is there any way to evade the immune system?

14. Summary slide - Many pathogens have evolved mechanisms that evade the specific immune system which has consequences for vaccination strategies. - Some pathogens can change their antigens avoiding the effect of immunological memory. - Antigenic variation occurs in diseases like malaria and trypanosomiasis and is one of the reasons why they are still so common in many parts of the world. - Antigenic variation also occurs in the influenza virus explaining why it remains a major public health problem and why at risk individuals require to be vaccinated every year. Evasion of the immune system

15. Summary slide • The absence or failure of some component of the immune system results in increased susceptibility to infection. • HIV attacks lymphocytes and is the major cause of acquired immunodeficiency in adults. • Tuberculosis (TB) survives within phagocytes and avoids immune detection. EVASION of immune system