1. Mr. E Murphy

4. Objectives Defence Systems General Defence System Specific Defence System Lymphocytes

5. Human Defence System Human body can distinguish between its own cells (self) and foreign cells or structures (non-self) General defence system is non specific Skin, mucous membranes and their secretions White blood cells and chemicals Specific defence system (immune system) Attacks particular pathogens, by producing antibodies or by killing infected cells The human body defends itself against bacteria, fungi and viruses that cause disease. Foreign bodies and cells are called pathogens

6. General Defence System Skin, clotting, lysozyme, sebaceous gland, mucous, cilia, acid, beneficial bacteria First line of general defence Consists of the destruction of pathogens by white blood cells, production of a series or proteins that kill or prevent pathogens from reproducing, and the inflammatory response Second line of general defence

7. Phagocytic White Blood Cells When cells are damaged by invading micro-organisms they release a large number of chemicals, which attract white blood cells into the bloodstream White blood cells engulf and destroy any bacteria, viruses or other micro-organisms that they meet These white blood cells are called phagocytes (last only a few days) Some phagocytes are called macrophages, as they are large and live a long time Macrophages can be found in the spleen, lymph nodes and other lymphatic tissue such as the tonsils, adenoids, and appendix

8. Phagocytic White Blood Cells Complement is a set of about 20 proteins found in the blood plasma Proteins are activated by infection, the end result is the bursting of viruses and other pathogens Defence proteins

9. Inflammation When cells are infected they release a chemical called histamine, which results in blood capillaries opening wider (dilating) and becoming more porous This leads to localised swelling, redness, heat and pain It also brings more white blood cells to the area to fight the infection Antihistamines Fever

10. Specific Defence System Specific defence system attacks particular pathogens This happens through the production of antibodies or when white blood cells destroy body cells that are infected with a particular pathogen Lymphocytes and monocytes Types of white blood cells Formed in the bone marrow Move from the bone marrow into the blood vessels and into parts of the lymphatic system such as lymph vessels, lymph nodes, the spleen, the thymus gland in the chest Lymphocytes and monocytes both react to pathogens in different ways

11. Specific Defence System Develop into white blood cells called macrophages Macrophages recognise foreign molecules (antigens) that are present on the surface of pathogens When a macrophage digests a pathogen, the antigens are displayed on the surface of the macrophage This results in the antigens stimulating the production of antibodies Monocytes

12. Specific Defence System Lymphocytes Fight infection in two different ways 1) Some lymphocytes attack body cells that contain antigens on their surface 2) Other lymphocytes produce antibodies

13. Specific Defence System Antigens include molecules from the coats of viruses and the cell walls of bacteria, fungi, and other micro- organisms Antigens can also be found in parts of foreign cells such as pollen grains, incompatible blood transfusions, transplanted tissues or organs, and cancer cells Antigen and Antibodies An antigen is a foreign molecule that stimulates the production of antibodies

14. Specific Defence System Antibodies form part of a family of proteins called immunoglobulins (Igs) A large number of antigens are displayed on the surface of a pathogen Antigen and Antibodies An antibody is a protein produced by white blood cells (called lymphocytes) in response to an antigen

15. Specific Defence System Antigen and Antibodies Antibodies help to dispose of antigens in the following ways: 1. Antibodies prevent viruses and bacteria from entering new host cells. The pathogens are then destroyed by phagocytes 2. Antibodies inactivate pathogens by causing them to clump together, allowing phagocytes to destroy the pathogens 3. Antibodies trigger the complement system, which results in the pathogenic cells being burst Antigen-antibody reaction is a highly specific reaction Each antigen stimulates the production of only one specific antibody

16. Specific Defence System

17. Duration of immunity After an infection is overcome, some of the antibody- producing lymphocytes remain in the body for a long time If a second similar antigen enters the body, these lymphocytes can rapidly produce large amounts of the specific antibody First contact with an antigen, it takes 14 days to produce the maximum number of antibodies The next time, antibodies are produced in large numbers in about 5 days

18. Specific Defence System Problems associated with the antibody-antigen reaction Disabled in people suffering from AIDS The body can sometimes produce antibodies against its own tissues, resulting in autoimmune diseases such as rheumatoid arthritis and multiple sclerosis Allergies can occur when the body makes antibodies against materials which should not be antigenic

19. Induced Immunity Induced immunity is the ability to resist disease caused by specific pathogens by the production of antibodies Active immunity Active immunity is the production of a person’s own antibodies in response to antigens that enter the body Active immunity develops after a person is infected by a virus or bacterium or after vaccination Long lasting as the lymphocytes remain in the body for a long time Natural active immunity Artificial active immunity A vaccine Cowpox and smallpox

20. Induced Immunity Passive immunity Passive immunity occurs when individuals are given antibodies that were formed by another organism Individual does not have to be infected with the pathogen Short-term resistance to infections Natural passive immunity Antibodies from a mother Artificial passive immunity Injection of antibodies

21. Induced Immunity

22. Advanced Study of Lymphocytes Lymphocytes are white blood cells or leucocytes Formed in the bone marrow Each lymphocyte has a round nucleus with very little cytoplasm B-lymphocytes and T-lymphocytes Lymphocytes are distinguished according to the location in which they mature B-cells mature in the bone marrow T-cells mature in the Thymus gland

23. B-cells When they have matured in the bone marrow, B-cells move out into lymphatic tissue, e.g. spleen and lymph nodes There are many millions of different B-cells Each B-cell is adapted to recognise only one specific antigen, which is usually present on the surface of a macrophage Each B-cell produces only one type of antibody When a B-cell comes into contact with the antigen to which it divides to produce a group of identical B-cells These cells, called plasma cells, produce large amounts of the required antibody Plasma cells only live for a few days but they can produce up to 200 antibody molecules per second during those few days Most of the B-cells die off once the infection has been overcome Some remain, allowing for a secondary immune response It produces antibodies in response to much smaller amount of antigen Produces antibodies much faster Produces much greater number so f antibodies than is the case with a first- time infection

24. B-Cells

25. T-cells T-cells move from the bone marrow into the thymus gland where they become activated Process is important in the early months and years and life T-cells do not produce antibodies They act against viruses and some bacteria

26. T-cells T-cells move from the bone marrow into the thymus gland where they become activated Process is important in the early months and years and life T-cells do not produce antibodies They act against viruses and some bacteria

27. T-cells Helper T-cells Recognise antigens on the surface of other white blood cells, especially macrophages Chemicals produced by helper T-cells, stimulate the production and activation of antibody-producing B- cells Helper T-cells are the main types of cells that are infected by HIV Aswell as stimulating B-cells, helper T-cells also stimulate killer T-cells to reproduce

28. T-cells Killer T-cells Killer T-cells attack and destroy abnormal body cells, including virus-infected cells or cancer cells Killer T-cells release a protein called perforin, which forms pores in the membrane of the target cell Water and ions flow into the target cells through these pores Target cell swells and bursts Cytotoxic

29. T-cells Suppressor T-cells Stimulated to grow by specific antigens Suppressor T-cells inhibit B-cells, other T-cells and macrophages, controlling the immune response by stopping different immune responses Can survive for a long time, often life Some stimulate B-cells to start producing antibodies again later in life Some may trigger the production of killer T-cells Memory T-cells are responsible for lifelong immunity from infections Memory T-cells

30. T-cells

31. Summary

32. Exam Papers 2010 HL Q 15 c ii) 2009 HL Q 15 c i)

33. Solutions 2. a) Blocks foreign objects entering b)Prevents pathogens entering the blood c) Trap pathogens and prevent them from entering the body d) Protect the respiratory system e) Kills many pathogens f) Surround and ingest pathogens g) Set of proteins which seek and destroy pathogens h) Prevents the spread of pathogens i) Kills bacteria P 386

34. Solutions 7. a) Not exposed, passive immunity b) Nutrients and antibodies from the mother c) Vaccination contains a small amount of the pathogen d) Bodies reaction to a foreign pathogen e) Clean the wound and act as a antibiotic f) Producing your own antibodies will last longer g) It allows for immunity to be increased h) Immune system is not functioning properly i) Their body sees different things as foreign P 386