Cells and the Immune System

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  • Cells and the immune system
    • Antigens
      • molecules that generate an immune response
      • found on the surface of cells
      • allows the immune system to recognise non-self/foreign materials
        • pathogens
          • organisms that cause disease
          • bacteria
          • virus
          • fungi
        • abnormal body cells
          • cancerous
          • pathogen infected
        • toxins
          • poisons
          • produced by bacteria
        • cells from individuals of the same species
          • organ transplant
          • blood transfusion
    • The Immune Response
      • Phagocytosis
        • macrophage recognises foreign antigen
          • macrophage is  type of phagocte
            • type of white blood cell
        • cytoplasm moves round the pathogen to engulf it
        • contained in a phagocytic vacuole
        • lysosome fuses with vacuole and releases lysozymes
          • hydrolytic enzymes
          • pathogen broken down
        • becomes an antigen presenting cell by presenting antigens on it surface
          • activates T-cells
            • white blood cell
            • receptor proteins on surface to bind to complementary antigens presented by phagocytes
            • helper T-Cells
              • releases chemical signals that activate cytotoxic T-Cells
              • activate B-Cells
                • white blood cell
                • produced in the Thymus
                • mature in the bone marrow
                • bind to antigens to form antigen-antibody complex
                • specific antibodies
                • clonal expansion
                  • division
                  • plasma cells
                    • secrete monoclonal antibodies
                  • memory cells
                • humoral response
            • produced in the Thymus
            • cellular response
      • Primary response
        • slow as their aren't many B-cells that make complementary antibodies to bind to it
        • shows symptoms
      • Secondary response
        • memory cells
          • T-cells
            • remember specific antigen and recognise it after on secondary infection
            • activated and divide to the correct type of T-Cell
          • B-Cells
            • remember specific antibodies
              • can be made much quicker
              • 2,000 antibodies per second
        • quicker clonal selection
      • immunity
        • Active immunity
          • Natural
            • memory cells
            • immune after catching a disease
          • Artificial
            • vaccination
              • creates herd immunity
              • ethical issues
                • tested on animals
                • risky
          • requires exposure to antigen
          • takes longer
          • produces memory cells
            • long term protection
        • Passive Immunity
          • Natural
            • baby recieves antibodies from mother
              • breast milk
              • placenta
          • Artificial
            • injected with antibodies
          • doesn't require exposure to antigen
          • immediate protection
          • doesn't produce memory cells
            • short-term protection
      • Antigentic Variation
        • surface antigen chnages
          • secondary response no longer works
          • vaccines cannot be made for some pathogens
            • HIV
            • Influenza
    • antibodies
      • produce B-cells
      • two binding sites
        • allows agglutination
          • clumping pathogens together to allow easier engulfment
      • heavy chain
      • light chain
      • variable region
        • specific due to tertiary structure
      • constant region
        • the same for all antibodies
      • monoclonal antibodies in medicine
        • pregnancy tests
          • antibodies complementary to hCG
          • coloured beads
        • anti-cancer drugs
          • anti-cancer drugs can be attached to antibodies which are specific to the antigens on cancer cells
          • drug only accumulates where the cancer cells are
            • does not effect healthy cells
        • ELISA test
          • direct elisa
            • uses a single antibody complementary to the antigen being tested for
            • antigens fro patient sample bound to the inside of a well plate
            • detection antibody with attached enzyme is added
            • antibody will be immobilised
            • wash well out
            • substrate solution added
            • colour chanage if positive result
          • indirect elisa
            • antigens bound to bottom of well plate
            • patients sample added, specific antibodies will bind to antigen if present
            • wash well out
            • secondary antibodies added with specific enzyme attached
              • no primary antibodies, secondary antibodies will not bind
            • wash again
            • solution added
            • colour change if positive result
          • enzyme linked immunosorbent assay
          • used for medical diagnosis
            • HIV
            • allergies
          • uses enzymes
    • HIV
      • human immunodefienc virus
      • affects immune system
        • people become vulnerable to other infections
      • kills helper t-cells
        • host cell for HIV
        • can no longer stimulate phagocytes, cytotoxic T-cells nor B-cells
      • initial infection rapid replication occurs
        • flu-like symptoms
      • latency period
        • no symptoms will be experienced
      • HIV becomes AIDs
      • structure
        • attachment proteins
        • capsid
        • RNA
        • envelope
        • reverse transcriptase
      • replication
        • attachment protein s attach to receptor molecules of helper T-cell
        • capsid is released into cell
        • uncoats
        • releases RNA
        • reverse transcriptase makes complementary DNA strand from viral RNA temlate
        • double stranded DNA is inserted into human DNA
        • host cell enzymes make viral proteins from viral DNA in the human DNA
        • viral proteins assemble new viruses which bud off to infect other cells
      • no cure or vaccine
        • antiviral drugs can slow progression
      • STD
    • antibiotics
      • kill bacteria by interfering with metabolic reactions
      • target bacterial enzymes and ribosomes
      • cannot target viruses as they don't have their own enzymes or ribosomes, they use host cells
      • antiviral drugs target the very few virus-specific enzymes that exist

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