Immunology and disease

• Bacteria


  Prokaryotic cells, genetic information stored in circular strand of DNA
• Viruses


  Consist of nucleic acid enclosed in protein coat, genetic material can be DNA or RNA
• Bacteria


  Do not require a host to survive
• Viruses


  Are entirely dependent on their hosts and cannot survive without them
• Bacterial diseases


  • Tuberculosis (TB)
  • Cholera
• Tuberculosis (TB)


  Caused by Mycobacterium tuberculosis, infects phagocytes in lungs, bacteria lie dormant in tubercles
• Weakened immune system


  Bacteria become active again, destroy lung tissue, lead to breathing problems, coughing, weight loss, fever
• Viral infections


  • HIV (causes AIDS)
  • Smallpox
  • Influenza
• HIV


  First symptoms include fevers, tiredness, headaches, then HIV antibodies appear, eventually leads to weakened immune system and AIDS
• Other infections


  • Athlete's foot (fungal)
  • Malaria (transmitted by mosquito vector)
• Antibiotics


  Kill bacteria or inhibit their growth, examples include penicillin
• Bactericidal antibiotics


  Kill bacteria by destroying their cell wall
• Bacteriostatic antibiotics


  Inhibit bacterial growth by stopping protein synthesis and nucleic acid production
• Bacteria become resistant to antibiotics

  Through natural selection, resistant strains survive and reproduce
• There is an ongoing evolutionary race between organisms and pathogens
• Antibiotic resistant bacterial infections occur in hospitals, e.g. MRSA</b>
• Controlling spread of antibiotic resistant infections in hospitals

  1. Screen new patients, isolate and treat infected patients

  2. Use antibiotics only when needed and complete course

  3. Strict hygiene regimes like hand washing
• Physical barriers to infection

  • Skin (tough, keratin)
  • Stomach acid
  • Gut and skin flora (compete with pathogens)
• Non-specific immune responses


  1. Inflammation (increased blood flow, antibodies/cells leak out)

  2. Lysozyme action (enzyme kills bacteria)

  3. Interferon (prevents virus spread)

  4. Phagocytosis (white blood cells engulf pathogens)

  
• Antigen presenting cells


  Phagocytes that display pathogen antigens, stimulating specific immune response

  
• Cells involved in specific immune response

  • B cells (humoral response)
  • T cells (cell-mediated response)

  
• Memory cells


  Replicate when exposed to pathogen, remain in lymph nodes to provide faster immune response
• Cells in specific immune response

  • B effector cells (antibody producing)
  • T helper cells (stimulate B and T killer cells)
  • T killer cells (destroy infected cells)

  
• Active immunity


  Produced by immune system in response to antigen

  
• Passive immunity


  Introduced antibodies from another person or animal

  
• Types of immunity


  • Natural active
  • Natural passive
  • Active artificial (vaccination)
  • Passive artificial (antibody injection)

  
• Antibodies


  Globular molecules produced by lymphocytes, complementary in shape to specific antigens, can neutralise pathogens

  
• Pathogenic organisms


  Organisms which cause damage to its host or disease caused by a microorganism
• Infectious disease


  A disease that may be passed or transmitted from one person to another caused by a microorganism
• Carrier


  An organism or person which shows no symptoms when infected by a disease organism but can still pass the disease on to another person
• Disease Reservoir


  The place where a pathogen is normally found, which may be in humans or animals and may be a source of infection
• Endemic


  A disease which is always present in low levels in an area, often occurring at a predictable rate
• Epidemic


  A significant increase in the usual number of cases of a disease in a short period, often associated with rapid spread
• Pandemic


  An epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting many people
• Vaccine


  Uses non-pathogenic forms, products, or antigens of a micro-organism to stimulate an immune response in a person, providing protection against subsequent infection
• Antibiotics


  Substances produced by micro-organisms (usually a fungus) which kill or slow the growth of other micro-organisms (usually bacteria)
• Drug/Antibiotic Resistance


  When micro-organisms/bacteria are no longer affected by drugs/antibiotics they were previously affected by
• Vector


  A living organism that transfers a pathogen from one individual to another
• Toxin


  A chemical produced by a micro-organism which causes damage to its host
• Antigenic (sero) types of organisms

  Pathogens that cause the same disease but have different antigens on their surface, requiring different vaccines