Q21

What is the pathogenesis of serum sickness?

  • Type 3 hypersensivity
  • Phase 1: Formation of immune complexes
    • protein antigen, 1 week -> antibody -> blood -> Ag-Ab complexes
  • Phase 2: Deposition of immune complexes
    • Medium size, antigen excess most pathogenic
    • high pressure filtration, glomeruli, joints
  • Phase 3: Tissue injury caused by immune complexes
    • Acute inflammatory reaction ~day 10

Pass Criteria:

  • Bold
  • 3 Phases

How is the tissue damage caused?

  • IgG & IgM (C’ fixing Ab) bind to leukocyte Fc receptors.
  • Leukocyte recruitment and activation – release proteases/lysosomal enzymes -> damage
  • Deposition, activation and consumption of C’ and decreased C3 levels -> inflammatory reaction and tissue damage

What are some clinical features?

  • Fever
  • Urticaria
  • Arthralgia
  • Lymph node enlargement
  • Proteinuria

Pass Criteria:

  • 3 of 5 to pass

What are some other examples of Type III hypersensitivity?

  • Acute
    • Post streptococcal glomerulonephritis
    • Reactive arthritis
    • Arthus reaction
  • Chronic
    • Systemic lupus erythematosus
    • Polyarteritis nodosa
    • Other vasculitides
    • Possibly membraneous glomerulonephritis

Pass Criteria:

  • 3 examples

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