6.7 (responce to infection)

• what is an antigen?

  • macromolecule
  • stimulates immune responce
  • e.g proteins and polysaccharides
• what are leucocytes?

  white blood cells
• what are the two types of white blood cells? differences?

  • granulocytes (cytoplasm granules + lobed nuclei)
  • agranulocytes (no granules + smooth nuclei)
• examples of granulocytes?

  • neutrophil
  • eosinophil
  • basophil
• examples of agranulocytes?

  • monocyte
  • macrophage
  • lymphocyte
• What does the non specific immune system?


  • phagocytosis
  • inflammation
  • immediate results
• what is the specific immune system?

  • cell mediated + humoral responce
  • b lymphocytes
  • t lymphocytes
  • complimentary to the pathogen
  • have a time lag
• phagocytosis

  • bacteria enters phagocyte via endocytosis
  • bacteria held in phagosome
  • phagosome fuses with lysosome. forms pahgolysosome
  • lysosome digests pathogen
  • antigen from bacteria held in a MHC + displayed on cell surface
• white blood cells in phagocytosis?

  • neutrophil
  • macrophage
• structure + function of neutrophil?

  • ingests bacteria
  • kills and digests it
• structure + function of macrophage?

  • in body tissue
  • present antigen on surface
  • releases cytokines
  • stimulates immune responce.
• inflammation process

  • damaged vessel releases histamines
  • vasodilation occurs
  • blood flow increases
  • white blood cell + plasma into infected tissue.
• what are antigen presenting cells?

  • macrophage
  • displays antigen from pathogen on cell surface
  • enhanced by recognition t cells
• what are the two types of lymphocytes?

  • b lymphocytes
  • t lymphocytes
• b lymphocytes


  • differentiate in bone marrow
  • provide humoral immune response
• t lymphocytes

  • migrate from bone marrow to thymus gland
  • provide cell mediated response
• cell mediated response

  • antigen presentation by MHC on surface of macrophage.
  • T cell binds to MHC via complimentary surface receptor
  • produces activated t helper cell + memory cells via clonal selection
  • t cells produce t helper cells which release cytokines.
  • stimulates t killer cells to divide by mitosis
  • forming active t killer cells and memory cells
  • active t killer cells release perforin which kills cell.
• humoral response

  • b cell binds to antigen presenting cell via complimentary surface receptor
  • b cell engulfs antigen and presents it on its cell surface
  • t helper cell binds to b cell
  • secretes cytokines
  • stimulating clonal selection of activated b cell
  • becoming plasma cells which produce antibodies and memory cells
• structure of antibody?

  • 4 polypeptides joined by disulphide bonds
  • 2 heavy chains, 2 light chains
  • constant region
  • variable region which has specific antigen-binding site determined by tertiary structure.
• how do antibodies destroy pathogens?

  • inflammation
  • neutralisation
  • agglutination
  • precipitation
  • opsonisation
• what is opsonisation?

  • binding antibodies to surface
  • marking pathogen for phagocytosis
• what is precipitation?

  • antigens become insoluble
• what is agglutination?


  • antigens joined together
  • causing clumping
• what is neutralisation?

  • masks exotoxins within the pathogen
• active immunity?


  • produces antibodies from exposure to antigen
  • natural active = exposure to antigen in environment
  • artificial active = after vaccination
• passive immunity?


  • produced via antibodies that are transferred from other organisms
  • natural passive = transfer of maternal antibodies
  • e.g from placenta or breast milk
  • artificial passive = injection of antibodies
• role of memory cells?

  produce faster secondary immune response by...

  • remaining in the blood stream
  • bind to specific antigen when second infection occurs
  • undergo rapid clonal selection via mitosis
• secondary immune response vs primary?

  • shorter lag time
  • higher concentration of antibodies
  • pathogen destroyed before showing symptoms
• vaccinations


  • dead or weakened pathogen injected
  • stimulates primary immune response
  • memory cells remain in blood so secondary immune response is faster
• what is herd immunity?


  • majority of population is vaccinated
  • so those susceptible are also protected
• factors affecting development of herd immunity?


  • communities who object to vaccinations
  • communities receiving info that vaccinations are harmful