Chapter 7: Cellular response in defence.

1. Unit 1: Cell Function and Inheritance Chapter 7: Cellular response in defence. Higher Human Mrs Smith

2. Learning Intentions • You should be able to describe self and non-self antigens as in ABO blood group system. • You should be able to explain the production of antibodies and the role of blood cells. • Describe phagocytosis and the function of lysosomes. • Know the differences between innate, acquired, active and passive immunity. • Describe what is meant by auto immunity and what causes allergy in the body. Mrs Smith

3. Previous knowledge • Every body cell has a membrane • There are proteins in and on this membrane (phospholipid bi-layer) • What are the 6 functions of these proteins? • What is an immune system?

4. THE IMMUNE SYSTEM We all get sick sometimes...but then we get better. What happens when we get sick? Why do we get better? Mrs Smith

5. Cellular Defence • We are constantly surrounded by an almost infinite number of micro-organisms – on surfaces, airborne, inside us, on our skin, in food, clothing. Everywhere. VIRUSES FUNGI BACTERIA

6. Random facts about bacteria • There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×1030) bacteria on Earth, forming much of the world's biomass • You can fit thousands upon thousands of bacteria on a pinhead. • There are approximately ten times as many bacterial cells in the human flora of bacteria as there are human cells in the body, with large numbers of bacteria on the skin and as gut flora.

7. Random facts con’t • One survey found 20,000 species of bacteria in a litre of seawater. • The number of scientifically recognized species of animals is about 1,250,000 (most are insects). There are almost 300,000 recognized species of plants. There are an estimated 10-100 million different species of bacteria.

8. back to Cellular Defence…. • Most micro-organisms are actually harmless, but a few species can cause disease if they enter our bodies and grow to sufficient numbers. • We call these microbes pathogens. • Of all the species of bacteria, only about 30% are pathogenic. And only a small percentage of that 30% can cause harm to human hosts.

9. So what is an immune system? • Immunity is the ability of the body to resist infection by a disease causing organism (pathogen) o to overcome the organism if it succeeds in invading and infecting the body. • Immunity can be • INNATE(non-specific) or • ACQUIRED (specific) Mrs Smith

10. IMMUNITY INNATE (nonspecific) ACQUIRED (Specific) Skin, HCl, cilia, mucus etc. ACTIVE PASSIVE ARTIFICIAL ARTIFICIAL NATURAL NATURAL Antibodies self made after vaccination. E.g. polio, measles. Antibodies pre-made by mother – breastmilk, across placenta. Various antibodies. Antibodies self made after infection. E.g. Chickenpox, flu Antibodies pre-made by other organism such as a horse. E.g. tetanus

11. INNATE IMMUNITY: Nonspecific When you were born, you brought with you several mechanisms to prevent illness.Thistype of immunity is also callednonspecificimmunity. Innate immunity consists of: • Outer barriers • Cellular response • phagocytosis • inflammatory reaction • NK (natural killer) and mast cells • Soluble factors Mrs Smith

12. INNATE IMMUNITY – INBORN and UNCHANGING • Nonspecific - the same response works against many pathogens. • This type of response is the same no matter how often it is triggered. • The types of cells involved are macrophages/neutrophils, natural killer cells, and mast cells. Mrs Smith

13. Physical skin hair mucous Chemical sweat tears saliva stomach acid urine INNATE IMMUNITY – The barriers Mrs Smith

14. INNATE IMMUNITY Cellular response Inflammatory response • chemical and cell response to injury or localized infection • eliminates the source of infection • promotes wound healing Step 1. Circulation to the site increases tissue warm, red and swollen Step 2. WBCs leak into tissuesphagocytes engulf and destroy bacteria Mrs Smith

15. POSITIVE indicate a reaction to infection stimulate phagocytosis slow bacterial growth increases body temperature beyond the tolerance of some bacteria decreases blood iron levels NEGATIVE extreme heatenzyme denaturation and interruption of normal biochemical reactions > 39° C (103°F) is dangerous > 41°C (105°F) could be fatal and requires medical attention INNATE IMMUNITY Cellular response Inflammatory response (cont’d) Fevers have both positive and negative effects on infection and bodily functions Mrs Smith

16. Phagocytosis – ‘Cell Eating’ • When foreign cells such as bacteria and viruses invade the human body the body will respond by attacking them. • This is done by white blood cells. • Types of phagocytic white blood cells are: • Monocytes • Macrophages: engulf pathogens and dead cell remains. • Neutrophils: release chemicals that kill nearby bacteria.

17. The reason for PUS • During an infection hundreds of white cells migrate to the infected area and engulf the infected bacteria by phagocytosis. Phagocytes and and dead pathogens accumulate causing PUS Mrs Smith

18. Phagocyte migration CELLS alive! Neutrophils and macrophages recognise chemicals produced by bacteria in a cut or scratch and migrate "toward the smell". Here, neutrophils were placed in a gradient of a chemical that is produced by some bacteria. The cells charge out like a "posse" after the bad guys. Mrs Smith

19. Macrophages • WBCs that ingest bacteria, viruses, dead cells, dust. • Most circulate in the blood, lymph and extracellular fluid. • They are attracted to the site of infection by chemicals given off by dying cells. • After ingesting a foreign invader, they “wear” pieces of it called antigens on their cell membrane receptors – this tells other types of immune system cells what to look for. Mrs Smith

20. Macrophageand E. coli Mrs Smith

21. Macrophage ingesting yeast CELLS alive! This human macrophage, like the neutrophil, is a professional "phagocyte" or eating cell (phago = "eating", cyte = "cell"). Here, it envelops cells of a yeast, Candida albicans Mrs Smith

22. Neutrophils • WBCs – are phagocytic, like macrophages • neutrophils also release toxic chemicals that destroy everything in the area, including the neutrophils themselves Mrs Smith

23. Neutrophil phagocytosing S. pyogenes, the cause of strep throat Human neutrophils are WBCs that arrive quickly at the site of a bacterial infection and whose primary function is to eat and kill bacteria. This neutrophil is ingesting Streptococcus pyogenes. Mrs Smith

24. Neutrophil killing yeast NEUTROPHIL  YEAST  One way that neutrophils kill is by producing an anti-bacterial compound called “superoxide anion“, a process called oxidative burst. Here, a neutrophil senses, moves toward and ingests a yeast. In the next two panels, oxidation can be seen by using a dye. Mrs Smith

25. Phagocytosis – summary • A phagocyte detects chemicals released by the bacterium and moves along a concentration gradient (low to high). • The phagocyte attaches to the bacterium and engulfs it in a vacuole formed by an infolding cell membrane. • The phagocyte has organelles called LYSOSOMES which contains digestive enzymes. Mrs Smith

26. Surround and attack! • What happens when the bacteria is under attack? • White blood cells senses bacteria. • White blood cell moves towards bacteria. • White blood cell begins to surround bacteria. • White blood cell surrounds bacteria. • White blood cell kills bacteria. Mrs Smith

27. The stages of attack. Mrs Smith

28. IMMUNITY INNATE (nonspecific) ACQUIRED (Specific) Skin, HCl, cilia, mucus etc. ACTIVE PASSIVE ARTIFICIAL ARTIFICIAL NATURAL NATURAL Antibodies self made after vaccination. E.g. polio, measles. Antibodies pre-made by mother – breastmilk, across placenta. Various antibodies. Antibodies self made after infection. E.g. Chickenpox, flu Antibodies pre-made by other organism such as a horse. E.g. tetanus

29. Remember immunity can be: • Immunity can be • INNATE(non-specific) we have just done this so, ........... On to – • ACQUIRED (specific) IMMUNITY

30. Your mom’s antibodies were effective for just a short time at birth, but your innate immune system can be activated quickly. It is always your first line of defense during an infection, but it can’t always eliminate the germ. • When this happens, your body initiates a focused attack against the specific pathogen that is causing the infection. This attack may lead to long-term protection against that pathogen. • This type of immunity is called acquiredimmunity, the customized second line of defense. Mrs Smith

31. Acquired immunity: Depends on the action of antibodies to combat antigens • Acquired immunity can be split into a further 2 groups: • PASSIVE (antibodies made by another organisms i.e. mother, horse) • ACTIVE (self production of antibodies) • Each with a natural and an artificial aspect to them.

32. Antigens • An antigen is a complex molecule such as protein or polysaccharide which is recognised as alien by LYMPHOCYTES (type of wbc). • The presence of an antigen stimulates WBC’s to produce special protein molecules called antibodies Mrs Smith

33. Antibodies • An antibody is a Y-shaped molecule. • Each of its arms bears a receptor ‘binding’ site which is specific to a particular antigen. • The body has 1000’s of different types of lymphocytes each capable of responding to one specific antigen and producing the appropriate antibody. Mrs Smith

34. IMMUNITY INNATE (nonspecific) ACQUIRED (Specific) Skin, HCl, cilia, mucus etc. ACTIVE PASSIVE ARTIFICIAL ARTIFICIAL NATURAL NATURAL Antibodies self made after vaccination. E.g. polio, measles. Antibodies pre-made by mother – breastmilk, across placenta. Various antibodies. Antibodies self made after infection. E.g. Chickenpox, flu Antibodies pre-made by other organism such as a horse. E.g. tetanus

35. Natural acquired immunity • Acquired active natural. • Acquired passive natural. • Both of these types of immunity require antibodies which are produced by LYMPHOCYTES. These are made in bone marrow. • There are two types of lymphocyte. • T-lymphocyte (T-cells) from the thymus • B-lymphocytes (B-cells) from other places. Mrs Smith

36. Acquired immunity : Natural - B lymphocytes • The antibodies are made by B-lymphocytes. • In the presence of antigens, the B-cells will multiply to produce many antibodies. • After the infection some of these B-cells will remain to serve as ‘memory cells’ – ready to respond more quickly if body is exposed to same antigens.

37. The production of extra-cellular molecules (antibodies) that deal with specific foreign material is called a HUMORAL RESPONSE. • B-lymphocytes are matured in the bone marrow. • Leukaemia.

38. T-Lymphocytes – Helper T cells • These do not kill pathogens directly. • These cells patrol the body, and on recognising foreign antigens, the activate killer T cells, B cells and macrophages. Helper T-cell – the judge that identifies germs and orders their destruction

39. Acquired immunity : Natural - T lymphocytes • The second type of Lymphocytes are T-Lymphocytes • AKA killer T cells.

40. T-Lymphocytes – Killer T cells • A killer T cell will attack and destroy body cells (self antigen markers) that signal (by foreign antigens) that they have been invaded by a pathogen. Killer T-cell – Kills germs. • The T –cell releases a chemical to destroy the cell and the pathogen in it. • This is called a CELL MEDIATED RESPONSE

41. Immunological memoryPrimary and secondary esponse • Primary response – after seeing a pathogen for the first time it takes a while before enough antibodies are found in the bloodstream. The infected person usually still gets sick. • Secondary response – happens when there is another exposure to the same antigen. Antibody production is rapid, and a higher concentration is reached and maintained for a longer time. Here disease is usually prevented. Mrs Smith

42. Immunological memory -memory cells • Following the first exposure to the antigen, some B- and T-lymphocytes specific to the antigen remain in the body as memory cells. • If exposed to the pathogen again memory cells quickly produce clones of antibody forming B-cells and Killer T-cells HERE THE PERSON HAS AQUIRED IMMUNITY IN A NATURAL WAY! Mrs Smith

43. Immunological memory -memory cells Mrs Smith

44. Essay Question – 2002 • Give an account of immunity under the following headings. • B-lymphocytes and T-Lymphocytes (7) • Macrophages (3) Mrs Smith

45. IMMUNITY INNATE (nonspecific) ACQUIRED (Specific) Skin, HCl, cilia, mucus etc. ACTIVE PASSIVE ARTIFICIAL ARTIFICIAL NATURAL NATURAL Antibodies self made after vaccination. E.g. polio, measles. Antibodies pre-made by mother – breastmilk, across placenta. Various antibodies. Antibodies self made after infection. E.g. Chickenpox, flu Antibodies pre-made by other organism such as a horse. E.g. tetanus

46. NATURAL PASSIVE IMMUNITY Natural – Antibodies from mother passes into baby’s blood via breast milk or across the placenta. This is temporary until baby’s own immune system develops. Antibodies (Y) are also found in breast milk. The antibodies received through passive immunity last only several weeks. While your immune system was developing, you were protected antibodies. These antibodies traveled across the placenta from the maternal blood to the fetal blood. Mrs Smith

47. Essay Question – 2009 • 2. A. Describe how immunity is naturally acquired. (10). Mrs Smith

48. IMMUNITY INNATE (nonspecific) ACQUIRED (Specific) Skin, HCl, cilia, mucus etc. ACTIVE PASSIVE ARTIFICIAL ARTIFICIAL NATURAL NATURAL Antibodies self made after vaccination. E.g. polio, measles. Antibodies pre-made by mother – breastmilk, across placenta. Various antibodies. Antibodies self made after infection. E.g. Chickenpox, flu Antibodies pre-made by other organism such as a horse. E.g. tetanus

49. Artificial Aquired immunity.....Active • Artificial – Vaccinations. Forced exposure to a “dead” pathogen. This exposure introduces the white blood cells to the antigens so they can produce antibodies. Memory cells remain, allowing a secondary response in needed. • Small pox vaccine is a harmless form of the pathogen • Polio vaccine is a weakened form of the vaccine. • Cholera vaccine is a dead microbe whose antigens are unaltered.

50. Vaccines con’t • No matter how the vaccine is made or what it contains, its job is to promote production of B and T cells and the formation of antibodies..... Then some will persist as memory cells. HERE A PERSON ACQUIRED IMMUNITY BY ARTIFICIAL MEANS! Mrs Smith