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Transcript
Unit 4 Immunology and Public Health Unit 4 – Immunology and Public Health 1. The Immune System a)Non-specific defences b)Specific cellular defences 2. Infectious Diseases and immunity a)Transmission and control b)Active Immunisation and Vaccination and the evasion of immune responses 1. The Immune System b) specific cellular defences By the end of this section you will be able to ….. • describe what is meant by Immune Surveillance • describe what is meant by Clonal Selection Theory • describe the specificity of lymphocyte receptors What do these pictures have in common? Immune surveillance • A range of white blood cell constantly circulate and monitor the tissues. • If tissues become damaged or invaded, these cells release cytokines, which increase blood flow resulting in specific white blood cells accumulating at the site of infection or tissue damage. Lymphocytes • Lymphocytes are made in the bone marrow from stem cells. • Some leave and mature in the thymus gland (Tlymphocytes) • Whilst others remain and mature in the bone marrow (B-lymphocytes) Lymphocytes • The body has a vast array of lymphocytes and each with different SPECIFIC functions. • It is therefore important for the body to create as many lymphocytes as possible since a specific response is needed for each type of infection! • THINK/PAIR/SHARE: What do you think we mean by a “clonal population of lymphocytes”? Clonal Selection Theory • https://www.yo utube.com/watc h?v=HUSDvSkn IgI&feature=re lated Pool of lymphocytes showing a variety of antigen receptors Clonal selection theory Clonal Selection Theory • The body has a vast array of lymphocytes, each with a single type of membrane receptor specific for one antigen. • When the receptor on a lymphocyte binds to a non-self antigen, it becomes activated. • This leads to the lymphocyte dividing repeatedly and cloning themselves • Thus, a clonal population of lymphocytes is produced. Clonal Selection Theory Surface receptor Y antigen Only B-Lymphocyte ____ is activated because the a_____ is complementary and specific s_____ to cell Y receptor shape. Clonal Selection Theory – EXPONENTIAL GROWTH What would you rather do? 1. work for a flat rate of £100 per week OR 2. start earning 1p but the salary doubles each week. • OPTION 1 – you make £5,200 per year. • OPTION 2 – you make £5,242.88 after only 20 weeks. After 52 weeks it becomes an inconceivable amount of money. Can you now …. • describe what is meant by Immune Surveillance • describe what is meant by Clonal Selection Theory • describe the specificity of lymphocyte receptors Quick Questions 1. Describe when a clonal population of lymphocytes would be produced in the body? 2. If each lymphocyte can only recognise one specific antigen, how is it possible that lymphocytes offer effective protection against a wide variety of pathogens? 1. The Immune System b) specific cellular defences By the end of this section you will be able to ….. • describe the roles of 2 types of Tlymphocytes in response to infection • describe the role of B-lymphocytes in response to infection Lymphocytes • Lymphocytes respond specifically to: – Antigens on foreign cells – Cells infected by pathogens – Toxins released by pathogens • Collect 2 lymphocyte cards • Work in pairs • One person will learn about BLymphocytes • The other will learn about TLymphocytes • You will then teach your partner about your white blood cell Your teaching should allow you and the other pupil to be able to answer these questions… B-Lymphocytes T-Lymphocytes • Explain the link between B-lymphocytes and antibodies • What is special about these antibodies? • Describe the 2 effects of an antigen-antibody complex • Explain the role of a ‘memory B cell’ • How many groups of Tlymphocytes are there? • What are the names of the 2 groups? • Explain the link between lymphocytes and apoptosis • Explain the link between lymphocytes and cytokines • Explain how phagocytes and B-lymphocytes are involved B-lymphocytes B lymphocytes are able to recognise foreign antigens and engulf them. They then display the antigens on their surface waiting for a TH cell to release cytokines and activate it. Some will become clone antibody-producing B cells, others become cloned memory B cells Activated B lymphocytes Activated lymphocytes can produce a protein specific to the antigen called antibodies. The antibodies are able to bind to the antigen creating an antigen-antibody complex. Antibody action The binding of the antibodies causes the • inactivation of the pathogen (or the toxin it produces) and • pathogen to become more susceptible to phagocytosis B-Lymphocytes extra note Antibody receptor site Antigen A specific antibody is made by Blymphocytes. Antibodies are secreted into the lymph and blood where they make their way to the infected area. The antibodies recognise a specific antigen surface. Your teaching should allow you and the other pupil to be able to answer these questions… B-Lymphocytes T-Lymphocytes • Explain the link between B-lymphocytes and antibodies • What is special about these antibodies? • Describe the 2 effects of an antigen-antibody complex • Explain how role of a ‘memory B cell’ • How many groups of Tlymphocytes are there? • What are the names of the 2 groups? • Explain the link between lymphocytes and apoptosis • Explain the link between lymphocytes and cytokines • Explain how phagocytes and B-lymphocytes are involved T-lymphocytes There are two different types of T-lymphocytes or T-cells. - cytotoxic T cells (TC cells) AKA Killer T cells - helper T cells (TH cells) • Cytotoxic T cells cause apoptosis of an infected cell (programmed cell death) • remember NK cells! • Helper T cells become activated when they have come into contact with a foreign antigen and produce cytokines. TH Cells As seen before, there is a vast pool of different TH cells with different forms of antigen receptors. One of them will be specific to the antigen. Helper T-lymphocytes (TH Cells) ANOTHER way helper T cells can remove pathogens is when phagocytes engulf the foreign cell This phagocyte then presents the foreign antigen on its own surface, meaning one of the TH cells will be able to bind with it. Antigen presenting cell Helper T-Lymphocytes extra notes • When pathogens infect a tissue, some phagocytes capture the pathogen and display the it’s antigens on their surface • This display of antigen presentation, activates T-lymphocytes. • Once one version of the TH cell is activated, it goes on to multiply to give further clones of activated TH cells TC cells and cancer TC cells are also able to recognise antigens found on the surface of cancer cells. They are then able to bring about the lysis of large cancer cells. Antibody Production • http://www.youtube.com/watch?v=lrYlZ Jiuf18 • http://www.kscience.co.uk/animations/l ymphocyte.htm Can you now …. • describe the roles of 2 types of Tlymphocytes in response to infection • describe the role of B-lymphocytes in response to infection Quick Questions 1. 2 types of lymphocytes are produced. Explain the role of the lymphocyte which is involved in cells selfdestructing. 2. What is produced by B-lymphocytes during the immune response? 3. Name 3 possible effects of the protein produced by B-lymphocytes 1. The Immune System b) specific cellular defences By the end of this section you will be able to ….. • describe what is meant by immunological memory • state the benefits of having memory cells. FROM PRIMARY TO SECONDARY Primary response • When a pathogen infects the body, it takes time to raise an immune response and select the correct T and B cells (clonal selection) and produce antibodies. • This is called the primary response, and very often it is too slow to prevent the pathogen causing illness. Secondary response • However, if the person survives, and they come across the SAME pathogen a second time, they will have a much different secondary response! • This is because the body has created MEMORY CELLS • Some of the T and B lymphocytes that were produced by clonal selection after the first exposure survive long term as MEMORY CELLS. • When the SAME foreign antigen is recognised by these memory cells a second time, they very quickly form many clones of both T cells and antibodyproducing B cells. • This means that their are more antibodies produced faster and for a longer duration. • This is the secondary response. Can you now …. • describe what is meant by immunological memory • state the benefits of having memory cells. Quick Questions For each statement below state if it refers to the 1st or 2nd exposure of a pathogen a) Larger concentration of antibodies produced b) Clonal population of lymphocytes occurs faster c) Memory cells are produced d) Immune response is longer e) Illness occurs 1. The Immune System b) specific cellular defences By the end of this section you will be able to ….. • describe the role of T lymphocytes in recognising self and non-self • explain what is meant by an autoimmune disease in relation to lymphocyte regulation • state what is meant by the term ‘allergy’ and give examples of common allergic reactions Decide if each card is TRUE or FALSE Crohns disease, type 1 diabetes, Graves disease, psoriasis and rheumatoid arthritis are examples of autoimmune diseases. Chicken pox, CJD, legionnaires’ disease and meningitis are examples of autoimmune diseases. An autoimmune disease is caused by an overactive immune response in which the body’s own cells are destroyed. Autoimmune diseases can be caught from close contact with infected people. Treatment of autoimmune disease only serves to alleviate the symptoms, it does not cure the disease. Autoimmune diseases can be easily cured with a combination of antibiotics and anti-viral drugs. There is no known prevention for autoimmune disease. Children can be vaccinated against autoimmune diseases – this prevents them from getting ill in later life. Rheumatoid arthritis In rheumatoid arthritis, cytokines cause inflammation which will attack the bone and cartilage in joints, causing them to be replaced with fibrous tissue which leaves the joint less mobile than before. Type 1 diabetes • Destruction of Beta cells Graves disease Psoriasis skin condition that causes red, flaky, crusty patches of skin covered with silvery scales Crohns diseases Inflammation of the lining of the digestive system (IBD) Multiple Sclerosis Confusing self and non-self • T-lymphocytes have specific surface proteins that should be able to read the surface antigens of a cell and tell if it is self or non-self. • However, sometimes T-lymphocyte regulation can fail • T-lymphocytes fail to distinguish between the surface proteins of the body’s own cells and surface proteins on foreign cells and therefore attacks body cells. • The immune response against our own self cells is called autoimmunity. – Rheumatoid arthritis – Type 1 diabetes – Multiple sclerosis. Confusing self and non-self Allergies B-lymphocytes sometimes over-react to harmless substances like dust, pollen and feathers etc. or even medicines such as penicillin. The hypersensitive B-lymphocytes release antibodies which cause mast cells to release histamine. Some allergies are so severe that they can trigger anaphylactic shock where the histamine causes such a huge drop in blood pressure it can be life threatening. Can you now …. • describe the role of T lymphocytes in recognising self and non-self • explain what is meant by an autoimmune disease in relation to lymphocyte regulation • state what is meant by the term ‘allergy’ and give examples of common allergic reactions Questions – 12 minutes! 1) 2) 3) 4) What are the two types of lymphocytes? Where do T lymphocytes mature? Why are cytokines released at the site of infection? What is the name of the proteins found on cell surfaces that trigger an immune response? 5) Describe clonal selection. 6) a) What is autoimmunity? b) Give a condition linked to autoimmunity. 7) How does a TC cell lead to the destruction of an infected cell? 8) a) What does an activated B cell produce? b) How do these molecules bring about destruction of a pathogen? 9) What term is used to describe the first infection of the body by a pathogen? 10) If the body is re-infected at a later date, what is this known as? 11) Which cells are central to being able to fight off re-infection? 12) How does the immune response to the second infection compare to the first? Quick Questions 1. Choose the correct words from the box below to describe what is meant by the term allergic reaction > Under-reacts > Hyposensitive response > Over-reacts > Normally harmful substance > Hypersensitive response > Normally harmless substance 2. What cell is involved in autoimmune diseases? 3. Explain the role of this cell in autoimmune diseases BLOOD GROUPS A, B, AB, O Rhesus –ve and Rhesus +ve Blood groups! Agglutination Agglutination Tasks • Stick in the blood group tables and answer the following below it: 1. Explain why a person with blood group A cannot receive a transfusion from someone with blood group AB 2. Explain why a person with Blood group AB can receive a transfusion from someone with blood group A The Rhesus factor • In addition to having A or B antigens, some people have a further antigen on their blood cells. This is called antigen D and people who possess it are said to be rhesus positive (+ve). • Those that lack the antigen D marker are said to be rhesus negative (-ve). When does the rhesus marker become a PROBLEM? • Transfusion of Rh +ve RBC to a Rh –ve person must be avoided • And a child born to parents of different rhesus factors may also be at risk… When does the rhesus marker become a PROBLEM? When does the rhesus marker become a PROBLEM? • The immune system of a Rh -ve recipient would respond to Rh +ve red blood cells and produce anti-D antibodies. • These antibodies would persist leaving the person sensitised. • Any further transfusion of Rh +ve RBCs to the Rh –ve recipient would result in the person suffering from sever or fatal agglutination. How to test for your blood group https://www.youtube.com/watch?v=mM1UNY6iWnA#t=101 You have now completed Key Area 2 of Unit 4!