1. I MMUNE SYSTEM By Asma Marouf

2. U NDERSTAND HOW THE BODY DEFENDS ITSELF AGAINST INFECTION L.O: by the end of this session you should be able to: Recall how the human body protects it self from infection Illustrate how the cells of the immune system play a part in the protection against infection Recall the process of immune response

3. I NSIDE THE HUMAN BODY – IMMUNE SYSTEM Video [4 mins]4 mins What are the 3 types of cells produced by our immune system and what does each do?

4. T HE IMMUNE SYSTEM The immune system is composed of many interdependent cell types that collectively protect the body from bacterial, parasitic, fungal, viral infections and from the growth of tumor cells What is the front line defence?

5. P ATHOGENS An infectious disease is caused by pathogens, where they are said to be parasitic. Pathogens are organisms that live on or in their host, and gain nutrients from that host. There are two types of pathogens: Ectoparasites (i.e. bed bugs, louse, mites, ticks and fleas) attach themselves to the outside of the host. With the aid of specialized mouthparts they penetrate the skin and feed on their hosts blood. The parasites must have efficient structures for ‘hanging’ on because usually the host is quite mobile.

6. Endoparasites (i.e. bacteria, viruses, roundworm, tapeworm, flukes and protozoa) – live inside the host. Therefore they have developed different ways of gaining nutrients from the host. Endoparasites inhabit the human gut, blood vessels, blood cells, muscles, liver and lungs. Their lifecycles are usually very complex, and have adapted highly specialized features in order to live a ‘life on the inside’.

7. M ORE ABOUT PATHOGENS Many pathogens do not harm us because we have physical, chemical and cellular defences that prevent them from entering the body. If they do enter, then our immune system can prevent them from spreading though the body. The immune system is involved in the recognition and rejection of foreign cells and tissues.

9. G ENERAL DEFENCE SYSTEM The first parts of the general defence system are really barriers that stop the pathogens from entering the body These barriers try to stop all pathogens therefore they are considered non-specific defences. The physical barriers of our general defence system consist of the following:

10. The Skin - This was discussed in the excretion web page. It is a physical barrier that stops pathogens. Clotting - If the skin is broken the blood clot stops entry of pathogens. Sebaceous and sweat glands - These produce chemicals that kill bacteria. Lysozyme - This is in the saliva and the tear glands. It kills bacteria. Mucous membranes - These secrete mucus which lines many body parts. The mucous traps pathogens and prevents them from entering the body. Nasal hairs - These remove suspended micro-organisms from the air. Cilia - These small hairs beat to force mucus to the pharynx for swallowing to the stomach. Coughing helps in this process. Hydrochloric acid - This is found in the stomach. It kills micro- organisms. The vagina - It contains bacteria that produce lactic acid that prevents the growth of pathogens. Also the vagina has a low pH to kill bacteria as well as mucous membranes

11. T ASK – CREATE A CARTOON STRIP EXPLAINING HOW THE IMMUNE SYSTEM PROTECTS US FROM BACTERIA Spend 10-15 min

12. I NTRODUCING YOUR DEFENCE W HITE B LOOD C ELLS

14. Monocytes Exit blood vessels and turn into macrophages. Engulf invaders and debris by phagocytosis Non-specific Neutrophils Stay in blood vessels and engulf invaders and debris by phagocytosis Mainly non-specific but can be specific when directed by antibody targeting. Basophils Release histamines and participate in the inflammatory and allergic reactions Non-specific Eosinophils Chemically attack parasitic invaders similar to natural killer cells Non-specific LymphocytesForm T-cells and B-cells Specific except for Natural killer cells

16. T HE IMMUNE SYSTEM The immune system has two main components: Non specific immune response (discussed next lesson) Specific immune response

17. A NTIGENS Antigens are usually large complex molecules such as proteins or glycoprotein, although any complex can be antigenic. The body can then distinguish between local and foreign cells but only usually make antibodies in response to foreign antigens An antigen is any substance that when introduced into the blood or tissue induces the production of antibodies. Most cells possess antigens in their cell surface membrane which act as markers enabling cells to recognize each other.

18. A NTIGEN PRESENTATION

19. During antigen presentation the macrophage selects T-helper cells and B-cells that have membrane receptors that are complementary in shape to the antigens exposed T-helper cells (T h cells – see cell mediated response) recognise and bind to the displayed antigens

21. P ATHOGENS : K EEP OUT ! I MMUNE S YSTEM C ARTOON S TRIP 4cDefine pathogen and give three examples 4bDescribe one way our body prevents pathogens entering the body 4aDescribe two ways our body prevents pathogens entering the body 5cDescribe how phagocytes defend the body against disease 5bDescribe how t cells defend the body against disease 5aDescribe how b cells defend the body against disease 6cExplain the role of antigens and antibodies 6bExplain the role of memory cells 6aExplain how vaccines help us defend the body against disease 7cExplain how antibiotics help us defend the body against disease 7bEvaluate the effectiveness of vaccines, using examples 7aEvaluate the effectiveness of antibiotics, using examples

22. 4cDefine pathogen and give three examples 4bDescribe one way our body prevents pathogens entering the body 4aDescribe two ways our body prevents pathogens entering the body 5c Describe two types of white blood cell 5b Describe two ways a white blood cell would kill a pathogen 5aDescribe how phagocytes defend the body against disease 6cDescribe how t cells defend the body against disease 6bDescribe how b cells defend the body against disease 6aExplain the role of memory cells 7cExplain how vaccines help us defend the body against disease 7bEvaluate the effectiveness of vaccines, using examples 7aEvaluate the effectiveness of antibiotics, using examples

23. U NDERSTAND HOW THE BODY DEFENDS ITSELF AGAINST INFECTION L.O: by the end of this session you should be able to: Recall how the human body protects it self from infection Illustrate how the cells of the immune system play a part in the protection against infection Recall the process of immune response

24. Q UESTIONS 1. Explain how phagocytes work. 2. Explain the difference between antibodies and antitoxins. 3. Why do you think phagocytes are classed as a non-specific response whereas antibodies are a specific response? 4. What type of blood cells are involved in the immune response? 5. Why is there a delay between being infected and feeling the symptoms? 6. How do viruses make you feel ill? 7. How do bacteria make you feel ill? 8. What’s the difference between bacteria and viruses in how they replicate [make copies]?

25. 1. White blood cells. 2. Time needed for bacteria/virus to reproduce. 3. Viruses damage host cell as they reproduce. 4. Bacteria release toxins. 5. Bacteria can make identical copies, whereas a virus needs a host cell to reproduce. 6. Phagocytes envelop the pathogen within their cell and use enzymes to kill and digest the pathogen. 7. Antibodies are chemicals that are specific to each pathogen, and are released from white blood cells. They can send signal for help from other white blood cells. They can destroy the pathogen directly. They can also clump together to make phagocytosis easier. Antitoxins are chemicals that simply neutralise the harmful effects of toxins. 8. Phagocytes will attack all pathogens (non-self structures) the same way whereas the antibodies are made specifically according to the antigen structure on the surface of the invading pathogen.