Immune response ppt

• Pathogens


  Microorganisms that cause infectious diseases
• We transmit pathogens between people, but we don't transmit the "disease"
• Organisms that can be pathogenic

  • Bacteria
  • Viruses
  • Fungi (less commonly)
  • Protist
• Vaccines


  Make us immune to disease (contain dead/inactive pathogens or their antigens) but they don't stop us from being infected by pathogens
• Physical barriers to infection

  • Skin
  • Stomach acid
  • Mucous linings
• Non-specific immune response


  Against ALL pathogens
• Specific immune response


  Against a specific pathogen
• Types of "foreign" cells

  • Pathogens
  • Abnormal cells (e.g. cancer cells)
  • Transplanted cells
  • Toxins secreted by some pathogens
• Antigens


  Molecules (often proteins/glycoproteins) that trigger an immune response, usually found on the cell membrane
• Phagocytosis


  -Certain types of white blood cells are phagocytic

  -Capable of engulfing and digesting pathogens

  -Patrol all body tissues to seek out non-self antigens

  -Destroy the cells that have them (also destroy dead/damaged body cells)
• Phagocytes seek out pathogens, engulf them, and lysosomes containing lysozymes digest the pathogen. Waste products are then removed by exocytosis.
• After phagocytosis a few phagocytes become antigen-presenting cells

  Phagocytes that do not digest the antigens, but instead present them to T helper cells
• Lymphocytes (T & B cells)


  Their specific shaped receptor proteins/glycoproteins on the cell surface membrane bind to specific antigens, activating the immune cell
• Cellular immune response


  1. Specific helper T cell (Th) activated by antigen-presenting cell (APC) (receptor proteins on Th cell complimentary binds to antigen)

  2. Th cell divides (by mitosis) to form clone of more Th cells

  3. Th cell releases chemicals (cytokines) to activate specific cytotoxic T cells (Tc)

  4. Tc cells kill infected body cells by releasing perforin/enzymes causing cell lysis

  5. Th cell also activates specific B cells and phagocytes

  6. Specific memory T cells are produced
• Humoral immune response(happens at same time as cellular response)

  1. Specific B cell activated by chemicals from Th cell

  2. Divides by mitosis to form clones of plasma cells and specific B memory cells

  3. Plasma cells make and secrete specific antibodies (& memory cells)

  4. Antibodies (monoclonal) travel in blood, bind to antigens on pathogens, causing agglutination, then phagocytosis occurs to remove the pathogen

  (memory cells= next time infected there'll be many memory cells, having more of a chance to reach pathogens)
• Antibodies


  Quaternary level proteins produced by specific plasma cells in response to a specific antigen, with a binding site complementary to the antigen
• Antibodies are produced by organelles in plasma cells including nucleus (containing DNA), RER/ribosomes (make protein), Golgi (modify and package protein), vesicles (transport protein), and mitochondria (provide energy)
• Primary immune response


  First time the immune system responds to a specific antigen, illness occurs but memory cells are developed
• Secondary immune response


  When the same antigen enters the body again, memory cells are activated, leading to a faster and larger antibody response, destroying the pathogen before illness occurs
• Antigenic variation

  Some pathogens can change the shape of their antigens regularly leading to antigenic variation, which is a problem as previous memory cells do not have the complementary receptor proteins so it will not be activated by the new and differently shaped antigens= different strain of the virus
• Genetic mutation leads to different shaped antigens, resulting in different strains of a virus
• Vaccination


  Vaccines contain dead, weakened/attenuated pathogen or just the antigen of a pathogen itself, triggering an immune response and memory cells without (the dead/weakened pathogen) causing the full disease
• How vaccines work


  Vaccines contain antigens that trigger a primary immune response, leading to memory cells that can mount a faster secondary response if exposed to the real pathogen
• Antibodies may also be produced from vaccination, but they are not always needed for immunity
• Genetic mutation leads to

  Different shaped antigens
• Vaccinations


  • Vaccines contain a dead pathogen
  • Vaccines contain a weakened/attenuated pathogen (attenuated - not capable of reproducing)
  • Vaccines contain the antigen alone
• How vaccines give immunity to a disease

  1. Vaccine given containing the antigen

  2. Specific B cells activated (for the first time by helper T-cells etc)

  3. First clone of memory B cells produced

  4. Secondary exposure to antigen activates specific memory B cells

  5. Divide to form more plasma cells which produce more antibodies and faster

  6. More memory cells also made

  7. (Immunity has been acquired)
• Herd immunity- How do vaccines protect a population


  • A high % of the population is vaccinated
  • Reduces the chances of a person infected with the pathogen coming into contact with an unvaccinated healthy person
  • So, the pathogen cannot spread through the population causing disease
• Suggest why herd immunity doesn't always work

  -media representation/fake news
• Active immunity


  • Long-term immunity developed after being exposed to the antigen
  • Specific memory T and B cells are produced
  • Specific plasma B cells make and secrete specific antibodies
  • Natural - developed after having the disease
  • Artificial - vaccination containing (harmless) antigen
• Passive immunity


  • Short-term immunity after being given antibodies from another person
  • NO memory T or B cells are produced
  • Natural - Mother to baby (through milk or placenta)
  • Artificial - injected with antibodies
• Monoclonal antibodies


  Antibodies that have identical tertiary structures, produced by clones of one specific type of plasma cell, They all bind with the same specific antigen
• Uses of monoclonal antibodies (specific response) include

  • the treatment of cancer and other diseases
  • drug screening
  • home pregnancy kits
  • diagnosing disease
• Attach drugs to the antibody (use of monoclonal antibodies)


  mAb binds to specific antigens on cancer cell, drug is activated to kill cancer cell/prevent it from dividing by mitosis
• Medical diagnosis - the ELISA test (use of monoclonal antibodies)


  1. Enzyme Linked Immuno Sorbent Assay

  2. Use mAb's to detect presence of a specific antigen or detect presence of a specific antibody in a sample

  3. Samples include Blood/ urine/ saliva / other fluids

  4. Presence of antigen/antibody detected by colour change
• ELISA test plate - a number of samples from different people tested together, positive quickly identified by a colour change, each sample goes into a well
• Using monoclonal antibodies to detect presence of a specific antigen e.g. to differentiate between Chlamydia & gonorrhoea

  1. Specific to antigen on pathogen (monoclonal antibody coated well)

  2. In sample from infected person (antigen binds to antibody)

  3. Antibody also specific to antigen (enzyme linked mAb binds to immobilised antigen)

  4. Washing between stages is important to remove unbound antigens/antibodies 5. Substrate added & converted by enzyme into colour product
• Ethical issues associated with the use of vaccines and monoclonal antibodies

  -Vaccines are tested on animals

  -Human trials include health risks

  -Possibility of side effects

  -Animals are used to produce mAbs
• How the immune system recognises foreign cells

  • Specific shaped proteins/glycoproteins on the surface called (non self) antigens usually on the membrane
• Non specific responses examples

  (against all pathogens)

  • phagocytosis
  • inflammation