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  • Chapter 8 - Defence Against Disease*Defence Against DiseaseChapter 8

    Pages 245-284RBCLeukocyte (WBC)Leukocyte (WBC)

    Chapter 8 - Defence Against Disease

  • *ImmunityInfection:Defn: entry of a pathogen into the body of a organism (host) that might cause disease.

    ImmunityDefn: reactions that occur in a person in response to an infection

    The immune systemThe 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.

    Non- Specific Immunity: involves a natural immunity that is non-specific.

    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)

    Chapter 8 - Defence Against Disease

  • Self and Non-selfAll 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

    Chapter 8 - Defence Against Disease

  • AntigensThe 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 responseHow Does The Body Know What Cells To Attack

    Chapter 8 - Defence Against Disease

  • IMMUNE SYSTEMConsists of Three Lines of Defence

    Chapter 8 - Defence Against Disease*

    Pathogen invades Tissue/ CellNon Specific DefenceSpecific Defenceacquired resistanceBarriers

    1Physiological

    MechanismsChemicalMechanismsPhagocytes and NK CellsInflammationBasophilsMast Cells and plateletsHistamines & phagocytosisB Cells

    T Cells

    Memory Cells

    Antibodies

    Humoral Immunity

    Cell Mediated Immunity

    3

    2

    Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease*Non-Specific Immunityreading: 246 250 Quick Check:1-7 Biozone: 147-148

    Chapter 8 - Defence Against Disease

  • Non-specific mechanismsPart of bodys natural immunityProvide protectionAre present at birthEither prevent entry of pathogens or destroy themLimit the onset and development of infectionDirected against a wide range of pathogens

    Chapter 8 - Defence Against Disease

  • *Non-specific mechanisms: Barriers: 1st line of defence

    Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease*The First Line of Defence

    The WallThe 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

  • Skin

    An intact skin acts as a barrier against entry by micro-organisms. A cut or abrasion will allow entry of bacteria or viruses.

    Hardening of outer layersProvides a physical barrierAnti-bacterial and anti-fungal secretionsProduced by sweat glands, sebaceous (oil) glands, bacterial flora of the skinLack of moistureLimits growth of microorganisms

    Chapter 8 - Defence Against Disease

  • *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

    Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease*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.

    PeristalsisDiarrhoea eliminates pathogens by movement towards the anus for elimination

    Vomiting also results in removal of pathogens from body

    The First Line of Defence continued.

    Chapter 8 - Defence Against Disease

  • *EnzymesLysozyme 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.The First Line of Defence continued.

    Chapter 8 - Defence Against Disease

  • Gastro-intestinal secretions

    HCl in stomach, alkaline fluids e.g. bile in duodenumAre of a pH which is outside the range of tolerance for many microorganisms

    Hairs and cilia

    Filter inhaled airRemove micro-organisms and other antigenic material (e.g. pollen)

    Chapter 8 - Defence Against Disease*The First Line of Defence continued.

    Chapter 8 - Defence Against Disease

  • *Non-specific mechanisms: 2nd Line of defence

    Chapter 8 - Defence Against Disease

  • *The Second Line of Defence

    The Dumb Soldiers

    Chapter 8 - Defence Against Disease

  • PHAGOCYTESPhagocytes (group of cells)(particular) white blood cellsformed in the bone marrowvery motile and can move between cellsengulf and destroy micro-organisms and foreign materials through phagocytosisinclude the following groups:

    Neutrophils

    Monocytes/ Macrophages

    Eosinophils

    Chapter 8 - Defence Against Disease*The Second Line of Defence continued

    Chapter 8 - Defence Against Disease

  • (a) SEM (4300x) : macrophage pulling rod-shaped E.coli towards it with long cytoplasmic extensions. Several bacteria on the macrophages surface are being engulfed(b) Events of phagocytosis

    Chapter 8 - Defence Against Disease

  • Monocytes Largest of the white blood cellsbecome 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

    NeutrophilsThe most numerous of the phagocytotic cellsGranulated nucleusAttacks bacteriaDie after engulfing bacterial pathogenTheir dead cells become the bulk of pus at woundsThe Second Line of Defence continued Macrophage destroying bacterial cells

    Chapter 8 - Defence Against Disease

  • Eosinophils can be phagocytotic.secrete enzymes to kill parasitic worms among other pathogins

    The Second Line of Defence continued

    Chapter 8 - Defence Against Disease

  • Non-phagocytic leucocytes -Basophil - contain granules of toxic chemicals that can digest foreign microorganisms. These are cells involved in an allergic response

    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 ...Basophils are a type of white blood cell (leukocyte). These cells help you fight infections by releasing histamine and other chemicals like heparin (antocoagulant)

    Chapter 8 - Defence Against Disease

  • LEUKOCYTES*

    LEUKOCYTES

    All produced in the Bone Marrow from Stem CellsGranular Leukocytes

    Have large, lobbed nuclei and distinctive granules in their cytoplasm Agranular Leukocytes

    Cytoplasm usually lacks granules and the nucleus is more roundedNeutrophils

    Most numerous WBCMain phagocytotic cellIngest bacteria and phagocytize dead cellsEosinophils

    Produce enzymes which detoxify foreign proteins and fight parasatistic infectionBasophils

    Produce and release heparin and histamine in response to injury or infectionLymphocytes

    (T and B)

    Some produce antibodies (B Cells) and others attack invading cells directly (T Cells)Monocytes/ Macrophages

    Largest WBC monocytes grow into macrophagesPhagocytotic cells that dont usually die after consuming pathogen

    Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease*The Second Line of Defence continued

    Chapter 8 - Defence Against Disease

  • Chapter 8 - Defence Against Disease*Complement Proteins

    Phagocytes are able to recognise foreign bodies with the aid of complement proteins.

    Complement proteins help phagocytes by:

    Sticking to invading microorganisms to become more readily identifiable by phagocytes.

    Some stimulate phagocytes to become more active.

    Some attract phagocytes to the site of infection.

    Some complement proteins destroy the membranes of invading micro-organism

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