The Immune System

1. The Immune System Home Team: Immunity Away Team: The Pathogens

2. Natural Immunity • The immune system can distinguish between our body and foreign material • Our immune system ‘fights’ infection through specific and non specific responses.:

3. Non-specific Responses: • React the same way to all infections • Have no memory of previous infection • The level of response is the same for each infection/exposure to the same pathogen • First and second lines of defence

4. Specific Responses: • React in a specific way to each infection • Have a memory of previous infection • Much greater response for second or subsequent infections/exposures to the same pathogen • Third line of defence

5. Group Activity • You are a group of students defending a circle on the ground. No one must enter this circle. • You have heard the enemy is coming • Come up with as many strategies as you can to keep them out of your circle • You have 5 minutes

6. First Line of Defence • Non-specific Immune Response and involves: • Skin – prevents pathogens entering the body • Scabs – form to prevent pathogens entering the body through breaks in the skin • Acids – e.g. in the stomach and vagina, can kill some pathogens • Enzymes – such as lysozyme in our tears and saliva, can kill some pathogens • Mucous and Cilia – can trap pathogens in the upper respiratory tract and carry them to the stomach • Learned Behaviours – such as washing hands and covering our cough, or avoiding sick people can prevent infection

8. Group Activity • You are a group of students defending a circle on the ground. The enemy has entered the circle. • You have combat training • Come up with as many strategies as you can to get them out of your circle • You have 5 minutes

9. Second Line of Defence • This is a Non-Specific Response and involves: • White Blood Cells • Phagocytes engulf and destroy micro-organisms and other foreign materials, this is known asPhagocytosis(refer to Blood and Heart Notes from term 1). Include neutrophils and monocytes. • Natural Killer (NK) Cells are white blood cells that kill virus infected cells

11. Complement Proteins • Assist in a number of ways • Stick to invading micro-organisms to allow them to be quickly recognised by phagocytes. • Attract more phagocytes to the site of infection • Destroy the membranes of invading micro-organisms

13. Interferon • Are proteins secreted from some cells when they are infected by virus particles. • Act on uninfected cells by making them more resistant to the virus. • Early response and can help us resist/prevent some viral infections. • Fever • Proteins in blood called Pyrogens increase body temperature which inhibits microbial multiplication and enhances the body’s repair processes

14. Inflammation • Prevents the spread of damaging agents to nearby tissues by forming blood clots to ‘wall’ of area • Disposed of debris and pathogens by increasing the number of white blood cells to the area • Sets the stage for repair processes • Symptoms include: Heat and Redness (increased blood flow to the area), Pain and Swelling (leaky vessels allow white blood cells and other proteins, like clotting factors, to enter tissues)

16. Individual Activity • Read pages 302-306 of Biology 2 text • Answer questions 2-7 on page 306

17. The third line of defence • Involves a specific response by the immune system to a particular infection. • Two main groups of lymphocytes (type of white blood cell) are involved in fighting the infection. • All lymphocytes are produced in bone marrow. • Some mature in the bone marrow into B lymphocytes or B cells. • Others leave the bone marrow and mature in the thymus gland into T lymphocytes or T cells.

18. Identifying foreign material • All cells have protein markers on their surfaces. • These markers are determined by genes called the major histocompatibility complex (MHC) • B cells and T cells recognise and ignore ‘self’ markers. They recognise and react with ‘non-self’ markers. • The marker that triggers a response from a B cell or a T cell is called an antigen (e.g. a virus protein coat or molecules of bacterial toxin).

20. B cells • B cells have antibodies on their surface • Antibodies attach to antigens • The antibody of a B cell recognises and binds to only one kind of antigen • Initially the body produces lots of different kinds of B cells with a different antibody on their surface Please draw Figure 16.1, p. 133

21. Antibody production • When an antibody recognises and binds to an antigen the B cell carrying that antibody reproduces lots of special cells called plasma cells and a few B-memory cells • Each plasma cell produces lots of the particular antibody and releases it into body fluids

22. Recovery Once antibodies of the right shape have been made in sufficient numbers, the invading organism is killed in one of a variety of ways. The antibody may: • cause the micro-organism to agglutinate (clump) so neutrophils can eat them • detoxify poisons produced by the pathogen • cause the micro-organism’s cell membrane to collapse

23. Immunity • People take time to recover because it takes time for the B-lymphocytes to clone plasma cells and for the cloned cells to produce enough antibody • Some B-lymphocytes produce B-memory cells which will recognise the pathogen next time it invades and cause much quicker antibody production and so the person may never again suffer from the disease. • The person is said to have natural active immunity.

24. How much antibody is produced? In what ways does the secondary antibody response differ from the primary antibody response?

25. Class Activity Antibody Mediated Immunity

26. T cells • Many different kinds of T cells are produced which recognise many different antigens. • Killer T cells kill cells infected by viruses. This stops the virus multiplying. • Helper T cells help recognise antigens and stimulate B cells. • Memory T cells provide long term immunity in the case that the virus is encountered again • Both B cells and T cells travel around the body in the lymphatic system. White blood cells are concentrated in lymphoid tissues, organs and nodes.

27. The lymphatic system

28. Individual Activity • Read pages 313-316 of Biology 2 text • Answer questions 16-19 on page 314

29. Individual Activity • Read pages 306-316 of Biology 2 text • Answer questions 8-15 on page 313 • Answer questions 16-19 on page 314

30. Group Activity • Each group will be given a scenario • Answer the questions and present your answers to the class

31. Acquiring Immunity • Specific immunity is Acquired Immunity (you only develop immunity following exposure. Immunity can be: • Active – antibodies are made in the body • Passive – antibodies are produced in one person and transferred to another

32. Memory B and T cells No Memory Cells

33. Read • Read page 136 of your white book: • The History of Inoculation and Vaccination against Small Pox

34. Immunisation • Vaccination is the process of introducing the vaccine into the body • Immunisation is the immune response to the vaccine that results in immunity • Vaccines (dead or live but weakened/attenuated pathogens and synthetic antigens) are used to activate the immune system against that specific disease, without causing the disease. Vaccines have the same antigens as the infective pathogen. Vaccines are usually injected or ingested.

35. Vaccination: • Usually involves a series of injections to bring on lasting immunity. This is the vaccination program and involves: • A first vaccination, in which the vaccine in introduced into the body for the first time • A primary response, during which plasma cells slowly produce small amounts of antibodies, resulting in short term immunity. Some memory cells are produced • A second vaccination, in which a second vaccine (or booster) is introduced into the body. Existing memory cells respond. • A secondary response, during which plamsa cells rapidly produce large amounts of antibodies. Further production of memory cells resulting in long term immunity.

36. Some pathogens secrete toxins which can be treated with Toxoidsin a similar way to vaccines. • Vaccine preventable diseases include: • Tetanus, Diphtheria, Pertussis (Whooping Cough), Hepatitis A, Hepatitis B, Varicella Zoster (Chicken Pox), Poliomyelitis, Measles, Mumps, Rubella (German Measles), Influenza, there are many more

37. Individual Activity • Read pages 317-326 • Answer questions 20-23 on page 322 • Answer questions 24-29 on page 326