1. THE IMMUNE SYSTEM Ch 40 Students know there are important differences between bacteria and viruses with respect to their requirements for growth and replication, the body’s primary defenses against bacterial and viral infections, and effective treatments of these infections.

2. Content Objectives Explain what causes disease. Describe how infectious diseases are transmitted. Explain what the function of the immune system is. Summarize what the body’s nonspecific defenses against invading pathogens are. Describe what an autoimmune disease is.

3. Disease Disease – Any change, other than an injury, that disrupts the normal function of the body. Some diseases are produced by agents, such as bacteria, viruses and fungi. Other causes are materials in the environment, such as cigarette smoke. Some are inherited, like hemophilia.

4. French Chemist Louis Pasteur and German bacteriologist Robert Koch brought about the idea known as the germ theory of disease. Concluded that infectious diseases were caused by microorganisms of different types, commonly called germs. The Germ Theory of Disease

5. Koch’s Postulates 1.The pathogen should always be found in the body of a sick organism. 2.The pathogen must be isolated and grown in the laboratory in pure culture. 3.When the pathogens are placed in a new host, they should cause the same disease that infected the original host. 4.The injected pathogen should be isolated from the second host. It should be identical to the original pathogen.

6. Agents of Disease Viruses – tiny particles that invade and replicate within living cells. Bacteria – cause diseases either by breaking down the tissues of the infected organism for food or by releasing toxins that harm the body. Protists – Malaria is caused by a protist that is spread from person to person by mosquitoes. Worms – Flatworms and roundworms are responsible for a number of serious human diseases. Fungi – most fungi are harmless but some cause serious problems to humans.

7. Nonspecific Lines of Defense Physical and chemical barriers to pathogens 1st Line of Defense Skin – most important Hair – eyelashes, nose hairs Cilia – in nose and throat; push pathogens away from lungs Secretions – mucous, stomach acid, sweat, tears, saliva, oil

8. 2 nd Lines of Defense –I–Inflammation (swelling) Vasodilation – blood vessels open up and allow white blood cells easier access the affected area –T–Temperature response (fever) –P–Phagocytes “eating cells” – engulf and destroy pathogens A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). Nonspecific Lines of Defense

10. Organs of the Immune System Tonsils and adenoids Lymph nodes Bone marrow Appendix Lymphatic vessels Lymph nodes Thymus Peyer’s patches Spleen Lymphatic vessels Lymph nodes

11. Lymphatic System Lymph nodeLymphatic vessel

12. Third Line of Defense Specific Defenses – If a pathogen is able to get past the body’s nonspecific defenses, the immune system reacts with a series of specific defenses.

13. Cells of the Immune System Bone graft Multipotential stem cell Hematopoietic stem cell Platelets Macrophage Erythrocytes Eosinophil Neutrophil Megakaryocyte Mast cell Basophil T lymphocyte Natural killer cell Dendritic cell B lymphocyte Lymphoid progenitor cell Myeloid progenitor cell Monocyte Marrow Bone

14. Blood Cells

15. Cells of the Immune System White Blood Cells Phagocytes - Neutrophils - Macrophages Lymphocytes –B-lymphocytes –T-lymphocytes –Killer Cells

16. Phagocytes Produced throughout life by the bone marrow. Scavengers – remove dead cells and microorganisms.

17. Neutrophils 60% of WBCs ‘Patrol tissues’ as they squeeze out of the capillaries. Large numbers are released during infections Short lived – die after digesting bacteria

18. Macrophages Larger than neutrophils. Found in the organs, not the blood. Made in bone marrow as monocytes, called macrophages once they reach organs. Long lived

19. Phagocytosis

20. Lymphocytes Produce antibodies B-cells mature in bone marrow then concentrate in lymph nodes and spleen T-cells mature in thymus B and T cells mature then circulate in the blood and lymph Circulation ensures they come into contact with pathogens and each other

21. B -Lymphocytes The antibodies are embedded in the plasma membrane of the cell and are called antibody receptors. When the receptors in the membrane recognise an antigen on the surface of the pathogen the B-cell divides rapidly. The antigens are presented to the B-cells by macrophages.

22. B -Lymphocytes

23. Some activated B cells  MEMORY CELLS. Memory cells divide rapidly as soon as the antigen is reintroduced. There are many more memory cells than there were clone cells. When the pathogen/infection infects again it is destroyed before any symptoms show.

24. Humoral Immunity Results in production of proteins called “immunoglobulins” or “antibodies”. Body exposed to “foreign” material termed “antigen” which may be harmful to body: virus, bacteria, etc.

25. Antibody Assembled antibody molecule Heavy chain Antigen-binding region Constant region Light chain

26. Activation of B Cells to Make Antibody Antigen-presenting cell Antigen Circulating antibody Antigen is processed Class II MHC Antigen Activated helper T cell Class II MHC and processed antigen are displayed Antibodies Plasma cell Antigen- presenting cell Antigen-specific B cell receptor B cell Lymphokines

27. Antibodies Also known as immunoglobulins Globular glycoproteins The heavy and light chains are polypeptides The chains are held together by disulphide bridges Each ab has 2 identical ag binding sites – variable regions. The order of amino acids in the variable region determines the shape of the binding site

28. Cell Mediated Response Helper T cells – turn on immune response Suppressor T cells – turn off immune response Killer (Cytotoxic) T cells directly attack antigen

29. T cells (Helper T cells and Cytotoxic T cells) T cells arise from stem cells in the bone marrow - they then travel to the thymus where the differentiate and mature. T cells ignore other cells with MHC molecules and they ignore free-floating antigens. They will bind with a antigen-presenting macrophage (a macrophage possessing a MHC-antigen complex). Effector cytotoxic T cells recognize infected cells with the MHC-antigen complex. They then destroy the cell with perforans (enzymes which perforate the cell membrane, allowing cytoplasm to leak out) and other toxins which attack organelles and DNA

31. Active and Passive Immunity Active immunity Lymphocytes are activated by antigens on the surface of pathogens Natural active immunity - acquired due to infection Artificial active immunity – vaccination Takes time for enough B and T cells to be produced to mount an effective response.

32. Active and Passive Immunity Passive immunity B and T cells are not activated and plasma cells have not produced antibodies. The antigen doesn’t have to be encountered for the body to make the antibodies. Antibodies appear immediately in blood but protection is only temporary.

33. Active and Passive Immunity Artificial passive immunity Used when a very rapid immune response is needed e.g. after infection with tetanus. Human antibodies are injected. In the case of tetanus these are antitoxin antibodies. Antibodies come from blood donors who have recently had the tetanus vaccination. Only provides short term protection as abs destroyed by phagocytes in spleen and liver.

34. Active and Passive Immunity Natural passive immunity A mother’s antibodies pass across the placenta to the foetus and remain for several months. Colostrum (the first breast milk) contains lots of IgA which remain on surface of the baby’s gut wall and pass into blood

35. Immunity: Active and Passive Artificially acquired Passive immunityActive immunity Naturally acquired Artificially acquired

36. Vaccination A preparation containing antigenic material: Whole live microorganism Dead microorganism Attenuated (harmless) microorganism Toxoid (harmless form of toxin) Preparation of harmless ags

37. Vaccination Injection into vein or muscle Oral

38. Allergies When the immune system responds to harmless substances Allergens – antigenic substances which do no real harm Allergens include house dust, animal skin, pollen, house dust mite and its faeces

40. Allergies Histamine causes blood vessels to widen and become leaky. Fluid and white blood cells leave capillaries. The area of leakage becomes hot, red and inflamed

41. Asthma Attacks can occur at any time Genes play a role in who develops asthma Breathing becomes difficult, sufferers experience wheezing, coughing, a tightness about the chest and shortage of breath. 1/7 children in UK has asthma, number is increasing. >1000 people die each year from asthma every year in the UK

42. Asthma Airways in asthmatics are always inflamed, during an attack this worsens. Fluid leaks from blood into airways and goblet cells secrete lots of mucus Airways can become blocked Muscles surrounding trachea and bronchioles contract which narrows airways further

43. Asthma Vaccines are being developed to make allergic responses less severe Designed to desensitise people so they do not produce antibodies to allergens Genetic tests may be used to screen children and then a vaccine could be given to prevent them developing asthma