4.1.1 Disease

• Herd immunity


  If a significant number of the population are immune, even those without immunity are protected
• SKIN


  • skin flora that competes with pathogens
  • a lower pH
• BLOOD CLOTTING

  • mesh of protein fibres plug up wounds
• WOUND REPAIR


  • tissue below the wound contracts
  • repaired with COLLAGEN fibres
• INFLAMMATION

  • tissue damage
  • mast cells release HISTAMINES AND CYTOKINES
  • redness, swelling, heat and pain
• CYTOKINES

  • attract phagocytes for phagocytosis
• HISTAMINE

  • VASODILATION - more blood in area so increased temp to kill pathogens
  • INCREASED PERMEABILITY OF BLOOD VESSELS - more tissue fluid pushed out to trap pathogens
• NEUTROPHIL

  • LOBED nucleus
  • NO major histocompatibility complex
  • under 10 mins for phagocytosis
• MACROPHAGE


  • ROUND nucleus
  • MAJOR HISTOCOMPATIBILITY COMPLEX
  • takes much longer for phagocytosis
• PHAGOCYTOSIS - macrophages

  • non-self pathogen antigen's discovered
  • phagosome formed in macrophage
  • fuses with lysosome
  • phagolysosome formed
  • hydrolytic enzymes (lysozymes) digest the pathogen
  • MAJOR HISTOCOMPATABILITY COMPLEX binds to antigens and presents the antigens on its plasma membrane
  • ANTIGEN PRESENTING CELL formed
• cell mediated response - T-cells


  • antigen on APC binds to T-cell CD-4 receptor which is complementary
  • clonal selection
  • T-helper cell is activated and produces interleukins that stimulate mitosis - clonal expansion
  • T-killer cells, T-memory cells and T-helper cells
• T-killer cells

  • release PERFORINS
  • make holes in plasma membranes
  • apoptosis
• T-helper cells


  • release interleukins that stimulate phagocytosis and division of B cells
• T-memory cells


  • remain in circulation to allow a rapid response to reinfection
• humeral response - B cells

  • B cell with antibody complimentary to antigen binds to antigen
  • OR is activated with interleukins from T-helper cells
  • clonal selection occurs and are activated
  • B cells divide by mitosis and clonal expansion occurs to form B plasma cells and B memory cells
• B plasma cells


  Clones of B lymphocytes that produce and recreate specific antibodies
• B memory cells


  remain in circulation to rapidly divide into plasma cells upon reinfection
• antigen-antibody complexes allow for


  • AGGLUTINATION
  • NEUTRALISATION OF TOXINS
  • OPSINONS
  • PREVENT PATHOGEN BINDING
• opsinons


  increase likelyhood of phagocytosis
• ANTIBODIES

  • variable region - antigen binding sites
  • hinge region - flexibility
  • constant region - binding to immune cells
  • disulphide bridges - hold polypeptide chains together
• Primary response​


  • Slow clonal selection + expansion​
  • Person feels symptoms​
• Secondary response


  • faster clonal selection and expansion
  • B and T memory cells are present
  • B memory cells divide and a large number of antibodies are produced in a short period of time
  • no symptoms experienced
• rheumatoid arthritis​


  • Immune system attacks cells in the joints​
  • Causing pain and inflammation​
  • Treatment: No cure​
  • Pain relief​
  • Immunosuppressants​​
• Autoimmune disease


  • immune system stops recognising self-antigens
  • attacks own cells
  • an abnormal immune response against normal tissues in the body
• Lupus​

  • Skin and joints​
  • Causes fatigue​
  • Can attack any organ in body​
  • No cure​
  • Anti-inflammatory drugs​
  • Immunosuppressants​
• Type 1 Diabetes​

  • Insulin-secreting cells in pancreas​
  • Insulin injections​
  • Immunosuppressants​
  • Pancreas transplant​
• Epidemic – Communicable disease spreads rapidly at local/national level​

  ​

  Pandemic – Communicable disease spreads rapidly across multiple countries​
• Preventing epidemics with vaccines​


  • Mass vaccination at start of epidemic prevents spread of pathogen to wider population​​
  • If significant number of population are immune, even those without immunity are protected​
  • This is herd immunity​
• Diseases without vaccines

  Malaria​

  • Plasmodium proctocista spends time in RBCs​
  • So is protected by self-antigens​

  HIV​

  • Enters T-cells and macrophages​
  • Disables immune system itself​
• Some vaccines need changing each year​


  • Eg influenza:​
  • There are different strains of the virus each year​ - immunologically different
  • So antibody produced needs to match the new antigen​
• Personalised medicine


  Medicine tailored to an individual’s genome​
• Synthetic Biology


  • Synthesis of new organisms​
  • Genetically modified organisms to produce a drug​
• Medicine and Biodiversity

  • Biodiversity is being reduced ​
  • Eg deforestation​
  • But only a fraction of life on earth has been investigated by scientists​
  • And we need to make sure we aren’t destroying organisms that could provide us with a life-saving drug​
• Aspirin​

  Based on compounds from willow bark​

  Pain killer​
• Digoxin​

  Based on digitoxin from foxgloves​

  Heart drug – to treat atrial fibrillation + heart failure​
• Risks of antibiotics:​

  ​

  • Side effects​
  • Severe allergic reactions​
  • Antibiotic resistance​
• • Penicillin was the first antibiotic discovered (Alexander Fleming 1928)​
  • Widely used by mid 20th century to treat bacterial infections​
• • MRSA – causes serious wound infections​

                 - resistant to methicillin​

  ​

  • C. Difficile – causes diarrhoea, fever, cramps​
• Tuberculosis (TB)​

  Bacteria​

  Animals + humans​
• Ring rot​

  Bacteria​

  Potatoes, tomatoes​