Immunity

    Cards (46)

    • What defensive mechanisms does our body have against pathogens?
      • Preventing the entry of pathogens by a variety of physical and chemical defences, such as the skin, mucous membranes, tears (containing the enzyme lysozyme, which destroys bacteria) and saliva
      • Inflammation (swelling and heating) of the region invaded by the pathogen, a process known as a non-specific inflammatory response
      • Recognising ‘foreign’ cells and targeting any pathogenic cells, a process known as a specific immune response
    • How do our cells recognise foreign cells
      • specific molecules found on the surface of cells (and viral particles) that enable them to be identified by the body
      • These molecules are usually proteins
      • They are often proteins that are part of the phospholipid bilayer, such as glycoproteins
    • What are the surface proteins found on to allow the body to recognise its own cells?
      • pathogenic cells
      • abnormal body cells - cancerous
      • toxins
      • cells from other individuals of the same species
    • What are antigens?
      protein that are used by the body to identify cells
    • What is an example of the importance of antigens in defending against pathogens?
      • white blood cells, phagocytes have surface proteins that act as receptors and bind to the protein, antigens
      • Enables pathogens to be engulfed and digested
      • the antigens are then presented on the cell surface of the phagocyte - antigen presenting cell
      • this then recruits other cells of the immune system leading to a specific immune response
    • What are the different antigens?
      • self antigens - do not stimulate an immune response
      • non-self antigens - stimulate an immune response
    • What is antigen variability?
      the antigens present on their surface change frequently due to genetic mutations
    • Why does antigen variability pose a problem for the immune system?
      • lymphocytes and memory cells produce a specific immune response
      • the surface receptors on lymphocytes and memory cells are complementary in shape to only one antigen
      • when the antigen changes the lymphocytes and memory cells can no longer bind
      • there is no secondary immune response, so get infected and suffer from disease again
    • What are phagocytes?
      white blood cells
    • What are the two types of phagocytes?
      • neutrophils
      • macrophages
    • What is the role of phagocytes?
      • recognise and engulf pathogens - phagocytosis
      • non-specific immune response
    • What is the process of phagocytosis?
      • pathogens release chemicals that attract pathogens
      • phagocytes move towards pathogen they can be identified due to present of pathogenic antigens
      • phagocytes attaches to the pathogen by binding to its antigens
      • phagocyte engulfs the pathogen within a phagocytic vacuole - endocytosis
      • forms a phagosome when neutrophil engulfs it
      • phagosome fuses with lysosome to form phagolysosome
      • lysosome release digestive enzyme lysozymes to digest the pathogen
    • What are the two types of lymphocytes?
      • T-lymphocytes
      • B-lymphocytes
    • What do mature cells have?
      specific cell surface receptors called T cell receptors - these have a similar structure to antibodies and are specific to one pathogen
    • What happens when t-lymphocytes are activated?
      • activated when they encounter their specific antigen
      • these activated t-lymphocytes divide by mitosis into either helper t cells or cytotoxic t cells
    • What is the role of t helper cells?
      1. assist other white blood cells in the immune response
      2. they release cytokines which stimulate: maturation of b-lymphocytes into antibody-secreting plasma cells, production of memory B cells, activation of cytotoxic t cels
    • What is the role of cytotoxic t cells?
      • patrol the body in search of antigen-presenting body cells
      • attach to the foreign antigens on the cell surface membranes of infected cells and secrete toxic substances that kill infected body cells
      • secrete perforins which create pores in the cell surface membrane of infected cells allowing toxins to enter
    • What happens when B-cells have the correct cell surface receptors?
      • bind to the antigens - clonal selection
      • the b-cells divide repeatedly by mitosis - clonal expansion differentiate into plasma cells and memory cells
    • What is the primary immune response?
      • small numbers of b-lymphocytes with receptors complementary to that antigen are stimulated to divide by mitosis
      • as they divide by mitosis, clonal expansion. large numbers of identical b-cells produced
      • some become plasma cells that secrete lots of antibody molecules - short lived
      • other b-cells become memory cells that are long lasting and remain in the blood
    • Explain the structure of antibodies?
      • quarternary structure
      • two 'heavy' polypeptide chains bonded by dilsulfide bonds to two 'light' chains
      • each polypeptide has a constant and variable region
      • at the end of the variable region is a site called the antigen-binding site
      • 'hinge region' where the disulfide bonds join the 'heavy' chains gives flexibility
    • What happens when an antigen and antibody are complementary?
      • the molecular structures fit into each other
      • it binds to one of the antigens
      • forming an antigen-antibody complex
    • What is agglutination?
      • pathogens become clumped together
      • each antibody has two binding sites
      • meaning they can bind to more than one bacteria at the same time
    • What is the secondary immune response?
      • same antigen is found in body
      • memory cells recognise the antigen and divide very quickly and differentiate into plasma cells
      • response is very quick - infection can be destroyed and removed
    • What is a vaccine?
      A vaccine is a suspension of antigens that are intentionally put into the body to induce artificial active immunity
    • How are vaccines administered and what do they produce
      • either by injection or orally
      • produce long-term immunity as they cause memory cells to be created
    • What are positives of vaccinations?
      • highly effective as they give lifetime protection
      • generally harmless as they do not cause the disease
    • What are negatives of vaccines?
      • poor response - cannot produce the antibodies
      • antigenic variation - variation causes the vaccine not to trigger the immune response
    • What is herd immunity?
      when a sufficiently large proportion of the population has been vaccinated making it hard for a pathogen to spread in a population
    • What is active immunity?
      antigen enters the body triggering a specific immune response - naturally acquired through exposure to microbes
    • What is passive immunity?
      acquired without an immune response - antibodies are not produced
    • What is artificial passive immunity?
      occurs when people are given an injection or transfusion of the antibodies
    • What is natural passive immunity?
      foetus receive antibodies across the placenta from their mothers
    • How is HIV transmitted?
      • sexual intercourse
      • blood donation
      • sharing of needles
      • from mother to child across placenta
    • What is the structure of HIV?
      • two RNA strands
      • proteins - include enzyme reverse transcriptase
      • protein coat - capsid
      • viral envelope - lipid bilayer and glycoproteins
      • attachment proteins
    • How does HIV replicate?
      • viral RNA enters the cell
      • reverse transcriptase enzymes produce a DNA copy of viral RNA
      • DNA copy is inserted into chromosome of the cell
      • each time the cell divides it copies the viral DNA
    • How is AIDS caused?
      • virus reduces the number of T helper cells
      • B cells are no longer activated
      • no antibodies are produced
      • decreases bodys ability to fight off infections leading to AIDS
    • Why can't antibiotics kill viruses?
      viruses are acellular, non-living. Under go no metabollic reactions
    • What can monoclonal antibodies be used for?
      • pregnancy tests
      • diagnosing HIV
      • detecting the presence of pathogens
      • detecting cancer cells
    • How can monoclonal antibodies be used to detect HIV?
      • HIV antigen is attached to a test plate
      • the blood sample being tested is passed over the test plate, if HIV antibodies are present they bind to antigen, the plate is then washed
      • a monoclonal antibody is then passed over the plate, it's antigen is the HIV antibody and will bind to it if it is present. Monoclonal antibody is attached to an enzyme
      • The enzyme catalyses a colour change, the more intense the colour the more HIV antibody present
    • What are ethical issues of monoclonal antibodies - animals?
      • all vaccines are tested on animals - animal testing is unethical in some cultures
      • animal-based substances are sometimes used in production of vaccines
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