P2 IMHM

• Immunology


  Study of the components and function of the immune system
• Immune System


  Molecules, cells, tissues and organs which provide non-specific and specific protection against microorganisms, microbial toxins, and tumor cells
• Primary lymphoid organ


  Provides protection
• Secondary lymphoid organ


  Capable of producing enzymes (e.g. S. aureus affects the skin, producing boils, pimples, scalded skin syndrome, carbuncles)
• Microorganisms that the immune system protects against

  • Bacteria
  • Parasites
  • Fungi
• Immune response


  Innate (non-specific)<|>Adaptive (specific)<|>Primary<|>Secondary
• Immunity


  State of non-specific and specific protection
• Ways of acquiring immunity

  • Natural
  • Artificial
• Active natural immunity


  Antigens enter body naturally with response of innate and adaptive immune systems, provides long term protection
• Passive natural immunity


  Antibodies pass from mother to fetus across placenta or infant in breast milk, provides immediate short term protection
• Active artificial immunity


  Antigens enter body through vaccination with response of innate and adaptive immune systems, provides long term protection
• Passive artificial immunity


  Antibodies from immune individuals injected into body, referred to as immune serum globulins (ISG), immune globulins (IG), or gamma globulins, provides immediate short term protection
• Principal function of the immune system

  To protect humans from pathogenic microorganisms
• Pathogenic microorganisms (Pathogens)


  Microorganisms capable of causing infection and/or disease
• Infection


  Ability of pathogen to enter host, multiply and stimulate an immune response
• Disease


  Clinical manifestations associated with infection
• Innate mechanisms (Innate immunity)


  First line of defense, non-specific
• Adaptive mechanisms (Adaptive immunity)


  Second line of defense, highly specific with memory
• Antigen


  Molecule which can bind to specific antibody but cannot elicit adaptive immune response
• Immunogen


  Molecule which can stimulate adaptive immune response
• Best immunogens are proteins with molecular weight > 10,000
• Hapten


  Small (low molecular weight) molecule unable to elicit immune response, combines with larger carrier molecule which together function as immunogen
• Properties of antigens that influence immune response

  • Size
  • Complexity
  • Conformation
  • Charge
  • Accessibility
  • Solubility
  • Digestibility
  • Chemical Composition
• Antibodies


  Glycoproteins that exist as monomers, dimers or pentamers of basic structure with 2 identical light chains and 2 identical heavy chains
• Fc fragment


  No antigen binding capacity, crystallizable at 4 degrees C, important for effector functions like opsonization and complement fixation
• Fab fragment


  With antigen binding capacity
• Hinge region


  Flexible region of the heavy chain located between CH1 and CH2, allows the molecule to bend to let each antigen-binding site operate independently
• Antibody


  Secreted form of immunoglobulin made by plasma cells
• Immunoglobulin


  Antigen binding molecules of B cells (B cell antigen receptors)
• Complement system


  Part of the innate immune system, consists of over 30 proteins and contributes 3 g/L to overall serum protein quantities
• Complement system pathways


  • Classical pathway
  • Alternative/alternate/properdin pathway
  • Lectin/MBL pathway
• Classical pathway


  1. C1q – C1r – C1s

  2. C4

  3. C2

  4. C4a

  5. C4b

  6. C2a

  7. C2b

  8. C4b2a

  9. C3

  10. C3a

  11. C3b

  12. C4b2a3b

  13. C5

  14. C5a

  15. C5b

  16. C5b6789
• Alternative pathway


  1. C3

  2. C3a

  3. C3b

  4. Factor B

  5. C3bB

  6. Factor D

  7. C3bBb

  8. C3

  9. C3a

  10. C3b

  11. C3bBb3b

  12. C5

  13. C5a

  14. C5b

  15. C5b6789
• Lectin pathway


  1. C1q – C1r – C1s

  2. C4

  3. C2

  4. C4a

  5. C4b

  6. C2a

  7. C2b

  8. C4b2a

  9. C3

  10. C3a

  11. C3b

  12. C4b2a3b

  13. C5

  14. C5a

  15. C5b

  16. C5b6789
• Common techniques for detection of RBC antigen-antibody reactions

  • Hemagglutination
  • Precipitation
  • Hemolysis
  • Agglutination inhibition
• Other techniques for detection of RBC antigen-antibody reactions

  • Radioimmunoassay (RIA)
  • ELISA
  • Enzyme immunoassay (EIA)
  • Immunofluorescence (IF)
• New & non-traditional laboratory methods for detection of RBC antigen-antibody reactions

  • Flow cytometry
  • Solid-Phase Adherence Test
  • Gel Test
  • RBC affinity column test