disease, vaccines and defences

• autoimmune disease


  disease resulting from an abnormal immune response in which the immune system treats 'self' antigens as foreign antigens and launches an immune response against them

  • targets healthy tissue
• autoimmune disease - lupus

  • immune system attacking cells in connective tissue
  • damages tissue and causes painful inflammation
  • skin, joint, heart, lungs
• autoimmune disease - rheutmatoid arthritis

  • caused by immune system attacking cell joints
  • damages tissue and causes painful inflammation
  • result in painful deformity and immobility
• epidemic


  rapid spread of disease through a high proportion of the population. A worldwide epidemic is called a pandemic
• active immunity


  immune system is activated and manufactures its own antibodies
• passive immunity


  antibodies are supplied from another source
• natural immunity

  immunity produced through normal life processes
• artificial immunity


  immunity produced after medical intervention
• opsonin


  type of antibody that attach to antigens on surface of a pathogen
• cytokines


  chemical messengers that bind to cell surface receptors and are involved in the immune response
• 1. monokines: released by macrophages and stimulate B cells to differentiate
  2. interleukins: stimulate B cell clonal expansion
  3. interferon: stimulated T killer cells
• skin cells made of kerotinocytes
• explusive reflexes


  when sensitive areas targetted - triggers coughing, sneezing and vomitting. - sudden explusion of air or fluid can carry microorganisms out with it
• inflammation


  swelling and redness of tissue caused by infection
• mast cells


  specialised cells that detect pathogens and then release histamine to initiate inflammation
• secondary defences


  activated after the pathogen has gained entry into the body. There are both specific and non-specific secondary defences
• clonal selection


  process by which T cells and B cells become activated when their cell surface receptors/ antibodies bind to a matching pathogen
• clonal expansion


  happens after clonal selection. activated T and B cells increase in number through cell division (mitosis) and begin to differentiate into specialised cells
• 1. mast cells in tissue detect pathogen and release cell signalling chemical called histamine
  2. histamine causes vasodilation which widens blood vessels and makes wall of capillaries in tissue more permeable
  3. WBC (phagocytes) circulating in bloodstream can leave bloodstream through wall of capillaries and reach the site of infection in tissue
  4. WBC attack pathogens at the site of infection in the tissue.
• 5. plasma also leaves bloodstream which results in an increase in tissue fluid - causes swelling (oedema)

  6. excess tissue fluid is drained into lymphatic system

  7. other immune cells (lymphocytes) are stored in lymphatic system come into contact with pathogens in drained tissue fluid and activate a specific immune response
• indirect transmission: vectors

  direct transmission: direct contact, sexual, blood, droplet infection, faeco-oral transmission, spores
• protists

  • eukaryotic organisms
  • mostly unicellular
  • can cause disease by entering host cells and feeding on contents as they grow
• viruses

  • not living
  • small particles which contain genetic material
  • invade and take over cells so they produce more copies of the virus
  • cell then dies and releases new virus particles which then infect healthy cells
• herd immunity


  when a significant proportion of population has been vaccinated, protects individuals who have not developed immunity
• ring vaccination


  when a disease case is reported, everyone in vicinity is vaccinated to prevent spread
• vaccination


  deliberate exposure to antigenic material that has been rendered harmless - activates specific immune system and causes immunity
• types of vaccines

  • live vaccines (similar pathogen)
  • toxoid vaccine (targets toxin)
  • attenuated (weakened version of pathogen)
  • antigen (loose antigen)
  • inactivated (dead pathogens)
• T killer cells


  attack and kill host body cells that are infected with pathogen. They recognise foreign antigens
• T helper cells


  release cell signalling molecules called cytokines that stimulate cells to develop and stimulate phagocytosis by phagocytes
• B memory


  immunilogical memory (antibodies) and remain in the body for a number of years
• T regulator cells


  specialised t cells which shut down immune system response after pathogens have been removed
• plasma cells (B cells)


  specialised B cells which circulate in blood, manufacturing and secreting antibodies which are specific to antigen
• T memory cells


  remain in bloodstream in low levels in case reinfection occurs and provides long term immunity. immunilogical memory
• physical defences


  prevent spread of pathogens
• chemical defences

  damage pathogens directly
• passive defences

  defences that are present before the infection
• active defence


  changes to defences in response to a pathogen infection
• callose

  • large polysaccharide
  • deposited at end of sieve plates
  • blocks spread of pathogens through phloem
  • blocks plasmodesmata
• tylose

  • balloon like swelling or projection that fills the xylem vessel and eventually blocks it
  • contain high concentration of anti-microbial chemicals
• T cell activation

  1. clonal selection: wait for antigen that is complementary to a t cell - antigens from pathogen or antigen presenting cells (macrophages)
  2. clonal expansion: t memory, helper, killer, regulator