Immunopathology Definition Type III reaction

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Immunopathology Definition - Type III reaction

• Type III reactions involve immune complexes( B/W
  IgM or IgG antibodies and a soluble antigen.
  These complexes are deposited in tissue, which
  activate complement. The kidney and skin are most
  often affected.
• Complexes likely induce disease by attaching to
  the Fc or C3b receptors on polymorphs, and
  trigger release of cytokines, attracting more
  PMNs, and initiating more complement fixation.

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Type III Hypersensitivity

• Glomerulonephritis
• Serum sickness
• Vasculitis

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Immunopathology Type III reaction -
Glomerulonephritis
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ImmunopathologyDefinition Type IV reaction

• The Type IV (delayed-type) reaction does not
  require antibody. Macrophages (epithelioid
  histiocytes) present antigen to T-cells. The
  activated T-cells then release cytokines (IL-12),
  which cause cell proliferation and recruit
  additional inflammatory cells to the site.
• A variant of type IV hypersensitivity is via
  cytotoxic T lymphocytes (CTLs). These CD8 cells
  kill target cells (tumor cells or virus infected
  cells) by recognizing foreign antigens on the
  cell surface complexed with MHC Class I kill
  via perforins, very similar to the way complement
  kills cells with the MAC

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Type IV Hypersensitivity (Delayed)

• CD4 T lymphocytes mediated
• - Granulomatous diseases
• - Tuberculin skin reactions
• - Transplant rejection
• - Contact dermatitis
• Cytotoxic T lymphocyte (CTL) mediated
• - Neoplastic cell lysis
• - Transplant rejection
• - Virus-infected cell lysis

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ImmunopathologyType IV Reaction
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ImmunopathologyType IV Reaction Contact
Dermatitis
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"A man's doubts and fears are his worst enemies."
William Wrigley Jr.