Immunity to parasites Flashcards
What are the 3 classes of parasites?
Protozoa (unicellular)
Helminths
Arthropods
How do parasites damage the host?
Compete for nutrients
Destroy cells
Cause mechanical blockage
How can parasites survive the immune system?
Avoiding or subverting immune system: Resistance to complement Survive inside phagocytes Manipulate dendritic cells (antigen presenting cells) Poor PAMP expression
Acquired immunity to protozoa can be cell mediated or humoral. Often effective immunity requires both pathways. Where do CMI and humoral immunity act? What cells drive them?
Antibodies - control parasites in blood and tissues, TH2
CMI - control intracellular parasites, TH1
How do protozoa evade immunity?
Avoid attachment and phagocytosis
Immunosuppression
Block antigen presentation
Alter surface antigens
How do helminths evade immunity? What cell drives their immune response?
Extracellular and too large for phagocytosis
Thick coat not penetrated by complement
TH2
What is the main immune response to helminths? What 3 things does this cause?
Strong TH2 response (driven by IL-4)
Causes eosinophils and mast cells at infection site
Raise IgE in circulation and eosinophilia
Release inflammatory mediators
Mast cells are the main effector cells in helminth immunity. What is their surface covered with? What do they do? What cell has a similar role?
IgE - antigen binding causes degranulation
Causes release of histamine
Eosinophils
What antibody do mast cells and eosinophils react too?
Ag-complexed IgE
How do antibodies control parasitic infections? (give 2 ways)
Direct damage or complement mediated lysis
Enhance phagocytosis
The immune response also changes gut physiology in response to worms. Does this kill the worms?
No - makes GI tract inhospitable for them
What does the immune response do to make the GI tract inhospitable for parasites?
Increase goblet cells = increased mucin, increased intestinal mobility and increased water into lumen
