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RBC Leukocyte (WBC) Leukocyte (WBC) Defence Against Disease Chapter 8 Pages 245-284 Chapter 8 - Defence Against Disease 1 Immunity Infection: Defn: entry of a pathogen into the body of a organism (host) that might cause disease. Immunity Defn: reactions that occur in a person in response to an infection The immune system • The immune system is able to distinguish foreign material from material that is made by the body. • The immune system has two kinds of responses to the entry of foreign material. 1. Non- Specific Immunity: involves a natural immunity that is non-specific. 2. Specific Immunity (adaptive immunity): the action of specific white blood cells (lymphocytes) to a specific antigen (pathogen or part of) which acts to neutralize the pathogen (also invokes production of memory cells) 2 How Does The Body Know What Cells To Attack Self and Non-self • All cells have marker proteins on their plasma membrane • These proteins are the products of the MHC genes. Each person has different MHC genes. • Therefore marker proteins are specific to each person/organism • Cells with the body's own marker proteins are accepted as “self”. These proteins are not antigenic to our own immune system. • Cells with foreign markers are recognised as “non-self”. These marker proteins are antigenic for us. How Does The Body Know What Cells To Attack Antigens • The term “antigen” originates from “antibody generator” • Defined as a substance that, when it invades the body, will stimulate the formation of a specific type of antibody • Usually protein or polysaccharide • May be free e.g. in the bloodstream, or attached to the cell surface of a pathogen • Critical in differentiating “self” and “non-self” • Self antigens on the cell membranes are called “markers”. • Those markers critical to the success of transplantation form the MHC (major histocompatability complex) • An antigen is typically a large complex molecule, not normally present in the body, that is capable of producing an immune response IMMUNE SYSTEM Consists of Three Lines of Defence Pathogen invades Tissue/ Cell Non Specific Defence Specific Defence acquired resistance Barriers Physiological Mechanisms Chemical Mechanisms Phagocytes and NK Cells Inflammatio n Basophils Mast Cells and platelets Histamines & phagocytosis B Cells T Cells Memory Cells Antibodies Humoral Immunity Cell Mediated Immunity 1 2 Chapter 8 - Defence Against Disease 3 5 Non-Specific Immunity reading: 246 – 250 Quick Check:1-7 Chapter 8 - Defence Against Disease Biozone: 147-148 7 Non-specific mechanisms • Part of body’s natural immunity • Provide protection • Are present at birth • Either prevent entry of pathogens or destroy them • Limit the onset and development of infection • Directed against a wide range of pathogens Non-specific mechanisms: Barriers: 1st line of defence 9 1. The First Line of Defence ‘The Wall” • The best action against micro-organisms is to prevent their entry into the body altogether. • The first line of defence against infection takes place at the body surfaces. Chapter 8 - Defence Against Disease 10 Skin • An intact skin acts as a barrier against entry by microorganisms. A cut or abrasion will allow entry of bacteria or viruses. – Hardening of outer layers • Provides a physical barrier – Anti-bacterial and anti-fungal secretions • Produced by sweat glands, sebaceous (oil) glands, bacterial flora of the skin – Lack of moisture • Limits growth of microorganisms The First Line of Defence continued…. Mucous Membranes • secreted by the cells lining your respiratory tract • traps bacteria which are then swept upwards to the back of the throat by the action of cilia. • some of the mucus and bacteria is then swallowed, coughed or sneezed out, or blown out through the nose. • promote growth of natural flora whose secretions limit pathogen growth 12 The First Line of Defence continued…. Natural Secretions • Many secretions of the body contain bactericidal agents. Tears and saliva contain lysozyme, an enzyme that cause bacteria to lyse or burst. Acid in the stomach also kills many bacteria. Peristalsis Diarrhoea eliminates pathogens by movement towards the anus for elimination Vomiting also results in removal of pathogens from body Chapter 8 - Defence Against Disease 13 The First Line of Defence continued…. Enzymes – Lysozyme in tears, saliva, sweat, nasal secretions and tissue fluids breaks up (lyses) the cell wall of certain bacteria Natural Flora • Many different bacteria are normally found on the skin, gut and in the vagina. These bacteria are harmless to the body and occur naturally. • The presence of these bacteria can inhibit the growth of pathogenic bacteria as they compete for nutrients and space. 14 The First Line of Defence continued…. Gastro-intestinal secretions – HCl in stomach, alkaline fluids e.g. bile in duodenum • Are of a pH which is outside the range of tolerance for many microorganisms Hairs and cilia – Filter inhaled air – Remove micro-organisms and other antigenic material (e.g. pollen) Chapter 8 - Defence Against Disease 15 Non-specific mechanisms: 2nd Line of defence 16 The Second Line of Defence “The Dumb Soldiers” 17 The Second Line of Defence continued … PHAGOCYTES Phagocytes (group of cells) • (particular) white blood cells • formed in the bone marrow • very motile and can move between cells • engulf and destroy micro-organisms and foreign materials through phagocytosis • include the following groups: 1. Neutrophils 2. Monocytes/ Macrophages 3. Eosinophils Chapter 8 - Defence Against Disease 18 (a) SEM (4300x) : macrophage pulling rod-shaped E.coli towards it with long cytoplasmic extensions. Several bacteria on the macrophage’s surface are being engulfed (b) Events of phagocytosis The Second Line of Defence continued … Monocytes • Largest of the white blood cells Macrophage destroying bacterial cells • become macrophages when they leave the bloodstream Macrophages • gather in various tissues such as the lungs, liver, kidneys and brain. • are particularly active against micro-organisms that can live inside the cells of the person they infect. • engulf bacterium Neutrophils • • • • • • The most numerous of the phagocytotic cells Granulated nucleus Attacks bacteria Die after engulfing bacterial pathogen Their dead cells become the bulk of ‘pus’ at wounds The Second Line of Defence continued … Eosinophils • can be phagocytotic. • secrete enzymes to kill parasitic worms among other pathogins Non-phagocytic leucocytes Basophil - contain granules of toxic chemicals that can digest foreign microorganisms. These are cells involved in an allergic response Basophils are a type of white blood cell (leukocyte). These cells help you fight infections by releasing histamine and other chemicals like heparin (antocoagulant) Mast Cells - similar to basophils, mast cells contain a variety of inflammatory chemicals including histamine and seratonin. Cause blood vessels near wound to dilate! and increase permeability of the capillaries a large connective tissue cell that contains histamine and heparin and serotonin which are released in allergic reactions or in response to injury ... LEUKOCYTES LEUKOCYTES All produced in the Bone Marrow from Stem Cells Granular Leukocytes Agranular Leukocytes Have large, lobbed nuclei and distinctive granules in their cytoplasm Cytoplasm usually lacks granules and the nucleus is more rounded Neutrophils Eosinophils Basophils Lymphocytes •Most numerous WBC •Main phagocytotic cell •Ingest bacteria and phagocytize dead cells •Produce enzymes which detoxify foreign proteins and fight parasatistic infection •Produce and release heparin and histamine in response to injury or infection (T and B) •Some produce antibodies (B Cells) and others attack invading cells directly (T Cells) Monocytes/ Macrophages •Largest WBC • monocytes grow into macrophages •Phagocytotic cells that don’t usually die after consuming pathogen 23 The Second Line of Defence continued … Chapter 8 - Defence Against Disease 24 The Second Line of Defence continued … Complement Proteins Phagocytes are able to recognise foreign bodies with the aid of complement proteins. Complement proteins help phagocytes by: 1. Sticking to invading microorganisms to become more readily identifiable by phagocytes. 2. Some stimulate phagocytes to become more active. 3. Some attract phagocytes to the site of infection. 4. Some complement proteins destroy the membranes of invading micro-organisms. Chapter 8 - Defence Against Disease 25 Compliment Proteins continued … Consequences of complement fixation Membrane attack complex results in lesions/holes in foreign cell. These result in death Amplifies inflammatory response because fixation causes the release of vasodilators and chemotaxis chemicals Foreign cell is made sticky and easier to phagocytise OPSONIZATION Complement: at least 20 different types of plasma proteins Usually in inactive form Bind to sugars or protein on foreign cell “complement fixation” The Second Line of Defence continued … Natural killer cells (NK cells) • are a type of lymphocyte (like macrophages) • police the body in blood and lymph • lyse and kill cancer cells and virus-infected cells • act against any such target (i.e. non-specific) • recognise certain sugars on invader’s surface • are not phagocytic: attack membrane of target cell and cause it, and its nucleus, to disintegrate The Second Line of Defence continued … Interferons. • are a group of antiviral chemicals • are secreted by some cells when they are infected by virus particles. • act on uninfected cells making them more resistant to the virus. • interfer with virus replication • stimulate macrophages to destroy virus infected cells • are produced very early during viral infection. • if a person develops a cold or flu, then the interferons have failed. 28 The Second Line of Defence continued … Fever Chapter 8 - Defence Against Disease 29 The Cause of Fever Biozone– Fever p152 30 The Second Line of Defence continued … Inflammatory response Four signs of Inflammation 1. Redness 1. Increased blood flow to area brings chemical and cellular agents to the site of injury and potential infection 2. Heat 1. Results from increased blood flow 3. Swelling 1. 2. Because blood vessels become more permeable and “leak” more fluid into surrounding tissues This encourages lymphatic return past stationary lymphocytes in lymph nodes 4. Pain • Adaptive because we protect area and prevent further damage Inflammatory response continued … Prevents spread of damaging agents to nearby tissues Disposes of cell debris and pathogens Sets the stage for repair The Second Line of Defence continued … Inflammation Chapter 8 - Defence Against Disease 33 Inflammation Chapter 8 - Defence Against Disease 34 Chapter 8 - Defence Against Disease 35 Key Elements of the 2nd Line of Defence FEATURE PRODUCED/ FOUND FUNCTION KEY FEATURES Leokocyte Monocytes Macrophages Neutrophils Basophils Eosinophils Nk Cells Mast Cells Stem Cells Interferons Compliment Proteins Vasodilation Inflammation Fever Interleukin-1 Prostaglandins Pyrexia - Cytokines Histamines Seratonin Chapter 8 - Defence Against Disease 36 Specific Immunity 3nd Line of defence 37 The Lymphatic System Function: • 1. take up excess tissue fluid and return it to the bloodstream • 2. absorb fats at the intestinal villi and transport to the circulatory system • 3. defend against disease Chapter 8 - Defence Against Disease The Lymphatic System Components include: – Bone Marrow (stem cells differentiate into lymphocytes – Lymphocytes: T and B (plasma & memory) Cells, Macrophages & NK cells – Lymph vessels – Lymph organs: Thymus, spleen, – Lymph nodes: tonsils, adenoids, armpits, groin etc – Lymph: fluid of the vessels containing cells of the lymph and foreign material (antigens) that have drained into it! Chapter 8 - Defence Against Disease Chapter 8 - Defence Against Disease 40 Chapter 8 - Defence Against Disease 41 Lymph Nodes • Biozone– The Lymphatic System p153 Chapter 8 - Defence Against Disease 42 Specific Immunity The Third Line of Defence Once a pathogen or other foreign material has entered the body, it is not only bombarded with your non-specific defences but is subject to attack by cells of immune system, the T and B Lymphocytes. This system is slower to take action but is more specific in its attack. T and B Cells are the bodies special forces 43 Specific Immunity The Third Line of Defence Chapter 8 - Defence Against Disease 44 The Second Line of Defence continued … • This line of defence requires a specific response to a particular infection by the immune system and results in adapted or acquired immunity. • The specific immunity acquired is generally long lasting, often for life. • This third line of defence involves special white blood cells known as lymphocytes. • Lymphocytes attack the particular invader, but also remember the attack (memory cells) so that a latter infection may be stopped more rapidly. Chapter 8 - Defence Against Disease 45 The Second Line of Defence continued … Two main groups of lymphocytes are involved in specific immunity: B Cells T Cells • B Cells mature in the bone marrow to produce • T Cells leave the bone marrow and mature in the thymus gland, where they turn into Tlymphocytes or T-cells. • B and T Cells work together and help each other!! Chapter 8 - Defence Against Disease 46 B Cells & the Humoral (Antibody Mediated) Immunity Ballistics Chapter 8 - Defence Against Disease B Cells & the Humoral (Antibody Mediated) Immunity • B Cells provide - Humoral (Antibody Mediated) Immunity • they can produce large quantities of antibodies in response to a foreign antigen • Must recognise ‘non-self’ antigen by binding to it to its receptor site • Requires a helper T- Cell to activate the B Cell • Once activated by a Helper T Cell, it divides madly producing two types of daughter cells including: • Plasma B cells • Memory B Cells • These cells are clones of the original activated cell and thuis produce the same antibody. This is known as the Clonal Selection Theory (see page 255) 48 B-Cells Chapter 8 - Defence Against Disease 49 B-Cells in Action Chapter 8 - Defence Against Disease 50 Chapter 8 - Defence Against Disease 51 B-memory Cells • When the plasma cells produce new antibodies and B-cells, some produced differentiate into other cells called B-memory cells. • B-memory cells have the same antigenantibody specificity as the original parent B-cell. • Memory cells can survive for many years or even life. • If a second infection ever occurs, the Bmemory cells react faster and more vigorously than the initial infection. • Remain in circulation, producing small quantities of antibody Chapter 8 - Defence Against Disease 52 B-Plasma Cells • Produce and secrete huge quantities of antibody molecules • These antibodies bind with antigens forming an antibody-Antigen complex • Plasma cells are relatively short living & broken down following infection Chapter 8 - Defence Against Disease 53 Antibodies“immunoglobulins” • B-cells have immunoglobulins on their surfaces. • Immunoglobulins are proteins that identify antigens. • Immunoglobulins are also called antibodies. • The immunoglobulins of each B-cell have a specific structure and recognise only one kind of antigen. • There are millions of antigens that the body must be able to respond. In response to this millions of different B-cells are produced with different immunoglobulins on their surfaces. • Self – tolerance is the ability of the immune system to recognise and ignore its own tissues early in development • Auto-immune disorder is the condition occuring when the body attacks own tissues Chapter 8 - its Defence Against Disease 54 The Structure of Antibodies Chapter 8 - Defence Against Disease 55 Action of Antibodies Chapter 8 - Defence Against Disease 56 Action of Antibodies Chapter 8 - Defence Against Disease 57 “immunoglobulins” more facts! • immunoglobulins – ig for short • Whenon the surface of a Lymphocyte – they are receptor sites. Off, they are antibodies! • both t and b cells have immunoglobulins on their surface • secreted immunoglobulins are called antibodies • it is the binding of antigen to receptor which triggers the specific immune response • during maturation, the genes that determine ig structure are continually being rearranged. this leads to new combinations of shape and charge in the antigen binding site • antibodies can combine with two antigens at once. this can cause clumping, or agglutination • the antigen – antibdy complex promotes phagocytosis • activates complement proteins • Chapter 8 - Defence Against neutralizes the binding site of an antigen Disease 58 Clonal selection Theory When an antigen enters the body it probably passes many B cells before it meets one with the immunoglobulan with which it can combine. In effect the antigen ‘selects’ the B cell that will lead to its death • Antigen ‘selects’ B Cell and its immunoglobulan • B cell rapidly reproduces (mitosis) to produce identical daughter cells • Each of these reproduces rapidly to produce a large clone of cells • Cell cloned in this way will have exactly the same DNA and antibodies • Most will differentiate into in plasma B cells, others into memory cells Chapter 8 - Defence Against Disease 59 T-Cells • When T-cells mature in the thymus, many different types of T-cells are produced which recognise many different antigens. Types of T - Cells Helper T - Cells Cytotoxic (Killer) T Cells Memory T Cells Helper T-cells (Th) • Release chemicals which attract phagocytes • Stimulate cell division in B-Cells • Produce chemicals that stimulate other T Cells Chapter 8 - Defence Against Disease 60 Chapter 8 - Defence Against Disease 61 T-Cells Cytotoxic T-Cells (Tc) • Another type of T-cell, cytotoxic T-cells (Tc), kills body cells that have been infected with a virus. • Tc cells kill the infected cell by secreting proteins that punch holes in the membrane of the cell and the contents ooze out. • Tc cells can only kill a virus when it is inside a cell. • Some Tc cells also destroy cancer cells. Suppressor T Cells (Tsc) • regulates immune response by turning it off when the infection passes Chapter 8 - Defence Against Disease 62 T-Cells Cytotoxic T-Cells (Tc) • Another type of T-cell, cytotoxic T-cells (Tc), kills body cells that have been infected with a virus. • Tc cells kill the infected cell by secreting proteins that punch holes in the membrane of the cell and the contents ooze out. • Tc cells can only kill a virus when it is inside a cell. • Some Tc cells also destroy cancer cells. Memory T Cells (Tm) • Remain in circulation (spleen) for many years after infection Chapter 8 - Defence Against Disease 63 Allergies and Hypersensitivity Chapter 8 - Defence Against Disease 64 Allergies and Hypersensitivity Chapter 8 - Defence Against Disease 65 Allergies and Hypersensitivity IgE binds with mast cells which are now sensitised to the allergenproducing histamines – inflammator y response – increase blood volume; permeability of vessels, Chapter 8 - Defence Against Disease 66 Blood Groups – Blood Antigens Chapter 8 - Defence Against Disease 67 Chapter 8 - Defence Against Disease 68 Rhesus Incompatibility • A red blood cell antigen, the rhesus factor is present on the red blood cells of a majority of people. Such people are rhesus positive (RH+). If the antigen is absent a person is rhesus negative (Rh-). If a person who is Rhand comes into contact with RH+ blood will respond by producing antibodies against the antigen. This can become critical in pregnancy Chapter 8 - Defence Against Disease 69 Rhesus Incompatibility Chapter 8 - Defence Against Disease 70 Acquiring Specific Immunity • Acquired Immunity is the term used to describe when antibodies are required to form immunity from a specific antigen. • Passive Immunity is when antibodies are received by an outside source (vaccination). • Passive naturally occuring Passive induced • Active Immunity is when antibodies are produced within a person (B-cells and T-cells). Chapter 8 - Defence Against Disease • Active naturally occuring Active induced 71 Acquiring Specific Immunity Chapter 8 - Defence Against Disease 72 Acquiring Specific Immunity Chapter 8 - Defence Against Disease 73 Acquiring Specific Immunity Chapter 8 - Defence Against Disease 74 Classification of Bacteria Gram Stains pages 214-215 • 1984, bacteriologist, Joachim Gram developed the gram stain • Gram stain distinguishes between two main groups of bacteria • Important stain to help identify which drugs are useful • Gram Positive bacteria take up the violet colour of the stain – Gram + have a cell wall layer of teichoic acid – Are particularly susceptible to penicillin and sulphonamide drugs • Gram Negative bacteria fail to take up the stain and by default stain pink – Gram – have no teichoic acid in their walls and smaller amounts of disaccharides and amino acids – Outer layer of lipid compounds enables these bacteria to resist penicillin and other drugs – Also makes phagocytosis of the bacteria very difficult – Effective drugs include streptomycin, tetracycline – S. empidermis: gram negative (susceptible to penicillin) 75 – S. ecoli: gram negative (resistant to penicillin)