IMMUNE SYSTEM Topic 6.3 IB Biology Miss Werba

NERVOUS & ENDOCRINE SYSTEMS TOPIC 6 - PHYSIOLOGY 6.1 DIGESTIVE SYSTEM 6.2 CIRCULATORY SYSTEM 6.3 IMMUNE SYSTEM 6.4 RESPIRATORY SYSTEM 6.5 NERVOUS & ENDOCRINE SYSTEMS 6.6 REPRODUCTIVE SYSTEM J WERBA – IB BIOLOGY 2

THINGS TO COVER Pathogens Antibiotics 1st line of defence: skin & mucous membranes Leucocytes & lymphocytes Antibodies & antigens Effects of HIV Cause, transmission & social implications of AIDS J WERBA – IB BIOLOGY 3

PATHOGENS Command term = DEFINE 6.3.1 PATHOGENS Command term = DEFINE Any organism or virus that causes disease in another organism eg. bacteria, fungi, viruses J WERBA – IB BIOLOGY 4

ANTIBIOTICS ARE FOR BACTERIA - NOT VIRUSES!!! 6.3.2 ANTIBIOTICS ARE FOR BACTERIA - NOT VIRUSES!!! Antibiotics inhibit specific metabolic pathways found in bacteria. eg. cell protein synthesis or cell wall formation Viruses have no metabolism or metabolic pathways of their own – they use host cell metabolism. Host cell metabolism is not inhibited by antibiotics. J WERBA – IB BIOLOGY 5

FIRST LINE OF DEFENCE: Physical barriers 6.3.3 FIRST LINE OF DEFENCE: Physical barriers Intact skin Intact mucosa Acidic skin secretions Keratinised Mucous Nasal hairs Cilia Gastric juice Acidic vaginal secretions Digestive enzymes in saliva & tears Urine J WERBA – IB BIOLOGY 6

FIRST LINE OF DEFENCE: Physical Barriers 6.3.3 FIRST LINE OF DEFENCE: Physical Barriers J WERBA – IB BIOLOGY 7

FIRST LINE OF DEFENCE: Skin & Mucous Membranes 6.3.3 FIRST LINE OF DEFENCE: Skin & Mucous Membranes Both act as a physical barrier (1st Line of Defence) Both host natural flora and fauna which compete with pathogens Both have lysozyme enzymes present to break down pathogens Both have a pH that is unfavourable to pathogens Mucous: is sticky - traps pathogens Skin: is a continuous, (hopefully) unbroken layer is dry – discourages growth/reproduction of pathogens has several layers of keratinized (hardened) cells J WERBA – IB BIOLOGY 8

SECOND LINE OF DEFENCE: Non-specific Response 6.3.4 SECOND LINE OF DEFENCE: Non-specific Response Cellular defences Systemic & Chemical defences Phagocytes Natural killer cells Inflammation Antimicrobial proteins (interferons & complement) Fever J WERBA – IB BIOLOGY 9

SECOND LINE OF DEFENCE: Non-specific Response 6.3.4 SECOND LINE OF DEFENCE: Non-specific Response J WERBA – IB BIOLOGY 10

SECOND LINE OF DEFENCE: Phagocytes 6.3.4 SECOND LINE OF DEFENCE: Phagocytes Are white blood cells – ie. leucocytes Phagocytic leucocytes occur in blood and body tissue fluids They detect pathogens They surround and engulf the pathogen (by endocytosis or more specifically, phagocytosis) Membrane forms around pathogen to form a vesicle Lysosomes digest contents of vesicles J WERBA – IB BIOLOGY 11

SECOND LINE OF DEFENCE: Natural Killer Cells 6.3.4 SECOND LINE OF DEFENCE: Natural Killer Cells Natural Killer (NK) cells are cytotoxic cells Meaning???? They can lyse (=burst) and kill other cells, including cancer cells and virus-infected body cells before the immune system is activated. They are a type of lymphocyte (T cell). NK cells secrete chemicals (interferons) that cause inflammation. J WERBA – IB BIOLOGY 12

THIRD LINE OF DEFENCE: Specific response 6.3.5 6.3.6 THIRD LINE OF DEFENCE: Specific response Cellular defences Chemical defences B cells Plasma cells Helper T (TH) cells Cytotoxic T (TC) cells Suppressor T (TS) cells Delayed hypersensitivity T (TDH) cells Memory cells Antigen-presenting cells (APC) Antibodies (immunoglobulins) Cytokines Complement Antigens J WERBA – IB BIOLOGY 13

THIRD LINE OF DEFENCE: Antigens & Antibodies 6.3.5 THIRD LINE OF DEFENCE: Antigens & Antibodies Antigen: a substance or molecule that is recognised by the body as foreign and causes an immune response (ie. antibody formation) Antibody: a protein that recognizes an antigen. J WERBA – IB BIOLOGY 14

THIRD LINE OF DEFENCE: Antibody Production 6.3.6 THIRD LINE OF DEFENCE: Antibody Production Antigen causes an immune response to produce antibodies. The antibodies that are produced are specific for that antigen. It is the B-lymphocytes that produce the antibodies . B-lymphocytes are produced in the bone marrow and carried in the blood. The antigen is presented to the B cell by an antigen presenting cell (APC) or Helper T (TH) cell J WERBA – IB BIOLOGY 15

THIRD LINE OF DEFENCE: Antibody Production 6.3.6 THIRD LINE OF DEFENCE: Antibody Production The lymphocyte capable of thwarting this antigen- bearing cell will divide many times, forming a clone. The clone produces a lot of the antibody to neutralise all of the infection. J WERBA – IB BIOLOGY 16

EFFECTS OF HIV HIV: Human Immunodeficiency Virus 6.3.7 EFFECTS OF HIV HIV: Human Immunodeficiency Virus It reduces the number of lymphocytes that are involved in antibody production. As a result, the infected person is more likely to develop a disease. These diseases are called opportunistic diseases and are the major cause of death of people with HIV and AIDS. J WERBA – IB BIOLOGY 17

AIDS: Cause AIDS: Acquired Immune Deficiency Syndrome 6.3.8 AIDS: Cause AIDS: Acquired Immune Deficiency Syndrome AIDS caused by HIV HIV penetrates lymphocytes, reducing their numbers over years Results in the loss of the ability to produce antibodies Results in lower immunity and the development of other illnesses AIDS is not a disease – but a collection of symptoms and/or opportunistic diseases that develops over the course of the HIV infection. J WERBA – IB BIOLOGY 18

6.3.8 AIDS: Transmission HIV transmitted through blood, sexual contact, body fluids, placenta, childbirth or breastfeeding. Blood and semen contain the highest concentration of HIV Transmission rates are uneven around the world. Transmission risk increases depending on society’s traditions, beliefs, behaviour. Condoms or other latex barriers only protection against transmission through sexual contact. J WERBA – IB BIOLOGY 19

AIDS: Social Implications 6.3.8 AIDS: Social Implications The treatment is expensive There is discrimination against victims There is a moral obligation of wealthy countries to help poorer countries; There are economic consequences (eg. loss of wage earners, etc) There is an increase in the number of orphans  become dependent on the government for support J WERBA – IB BIOLOGY 20

AIDS: Social Implications 6.3.8 AIDS: Social Implications Poverty increases risk as there is a lack of info (no schooling) and/or being forced to have sex in exchange for food/money Incidence of rape may also increase in poverty stricken nations  spreading HIV further Can’t get insurance because it is so expensive to treat people with HIV/AIDS J WERBA – IB BIOLOGY 21

Sample questions Q1 Which of the following statements about antibodies is correct? Antibodies are polypeptides. Antibodies are produced by the bone marrow. Antibodies are pathogenic foreign substances. Antibodies kill bacteria but not viruses. J WERBA – IB BIOLOGY 22

Sample questions Q2 Describe how phagocytic leucocytes may act as a defence against disease. [4] Q3 Outline the cause and transmission of AIDS. [5] J WERBA – IB BIOLOGY 23

Sample questions A1 A A2 phagocytic leucocyte occurs in blood and body tissue fluids; phagocytic leucocyte detects pathogen/foreign material; leucocyte surrounds/engulfs pathogen / endocytosis / phagocytosis; membrane forms around pathogen to form a vacuole; lysosomes digest contents of vacuoles; J WERBA – IB BIOLOGY 24

Sample questions A3 HIV/human immunodeficiency virus; reduces the effectiveness of the immune system / reduces the number of active lymphocytes / infects lymphocytes; loss of the ability to produce antibodies; leaving the infected person susceptible to other infectious diseases / AIDS is an accumulation of opportunistic diseases; can be transmitted by sexual intercourse/exchange of body fluids with an infected person; can be transmitted by blood transfusion/blood products from infected person; mothers can transmit to children while breast feeding/during pregnancy/birth; sharing hypodermic needles that have not been sterilized; J WERBA – IB BIOLOGY 25