Entamoeba histolytica III : Virulence, Immunology, and Host Immune Response

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Entamoeba histolytica III Virulence,
Immunology, and Host Immune Response
Bio 54 2002

• Andrew G. Campbell, Ph.D.

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The Life Cycle of E. histolytica
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Pathology
INTESTINAL
EXTRAINTESTINAL

Flask-shaped ulcer in colon
Large liver abscess
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Tissue Invasion
mucus
ameba
sloughed epithelial cells
neutrophils
epithelium
basement membrane
dead epithelial cells
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E. histolytica and the Immune Response

• Asymptomatic infections confined to the gut
• antibodies to E. histolytica are produced, but
  there is little cellular response
• Early Invasive disease
• Pathogenic amoebae strongly attract neutrophils
  to the site of tissue invasion
• Neutrophils fail to damage the parasite and
  instead are lysed, possibly contributing to
  tissue destruction
• Advanced invasive disease
• Ameba appear to induce specific immunosuppression
• Macrophages derived from the abscesses are
  functionally deficient
• T cell activity is also suppressed

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Immunomodulation by E. histolytica

• Mediated by various soluble factors
• Effects on Macrophages
• Inhibition of locomotion
• Reduced accessory cell function (reduced MHC II
  Ia)
• Modulation of cytokine production (TNF-a)
• Reduced responsiveness to IFN-g
• Reduced effector function (NO, O2-, H2O2 )
• Effects on T cells
• Reduced proliferative capacity
• Enhanced IL-4/IL-10 and reduced IFN-g
• Reduced CD4 T cell count
• Possible reduction in expression of cytokine
  receptors

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Protective Responses Versus Immunomodulation
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