Chapter 17- Immunity to parasites Flashcards
Estimated that _____% of the worlds population have parasitic infections.
30
Parasites are generally host specific and most of them cause chronic infections, a consequence of——————————————-?
Weak innate immunity and the ability of parasites to evade or resist elimination by adaptive immune responses
Do parasites typically infect acutely or chronically?
chronic
What is a benefit of their large size?
Lots of proteins, easy immune response
Explain the concept of stage specific antigens?
antigens that are specific to the life stages of the parasite differ as the parasite matures and changes.
What is a consequence of stage specific antigens?
by the time the immune system has responded to the infection the parsite expresses new antigens and is no longer a target for immune elimination.
What type of hypersensitivity can result fro parasitic infections?
Type III and indirectly type IV
Some parasites and their products induce _________ responses with concomitant fibrosis.
Granulomatous
Humoral responses are most effective against ____________?
extracellular stages of the parasite.
Who is responsible for Host defenses during intracellular growth?
Cell- mediated.
Protozoa are usually found?
in the gut, in macrophages, in blood, RBCs, and muscle
Can protozoa multiply in macrophages?
Yes some are reisistant to phagocytosis
What role does IgG and C3b play in immunity to paraistes?
IgG and C3b deposit on parasite membrane and enhance phagocytosis (similar to opsinization)
What is ablastin?
antibodies that inhibit protozoal replication by inhibiting said enzymes
What happens to infected RBC that carry protozoa antigens on their surfaces?
they are opsonized and removed by splenic macrophages and or destroyed by ADCC response/
What cells constitute the CMI response to parasites?
Cytotoxic T cells recognize the parasite antigens with MHC 1 and lyse the infected cells and Activated macrophages destroy intracellular parasites.
Phagocytic cells such as neutrophils and macrophages kill helminth parasites with what?
toxic proteins and reactive oxygen intermediates. some have thick cuticles and are resistant to cytocidal products of neutrophils and macrophages.
Do helminthes multiply in the host? are they intracellular or extracellular?
No they don’t, they are extracellular
Major mechanism of defense against helminth parasites involve?
TH2 cells, IgE antibodies, eosinophils.
Eosiniphil serum levels and IgE increase and remain high until?
the parasite is gone.
Eosinophils are normally present in peripheral tissues especially?
mucosal linings of the respiratory, GI and Urinary tracts. They are the most abundant at sites of parasitic, allergic or inflammatory diseases.
What level of immunity do helminth induce?
a low limited level.
Growth and differentiation of eosinophils is dependent on?
IL-3, IL-5, GM-CSF
why is IL-5 a significant cytokine?
because it also stimulates the release of eosinophils from bone marrow.
Eosinophil membrane receptors include Fc receptors for?
IgG, IgA, IgE, and also complement receptors.
the half life of eosinophils is?
12 days
What are some of the granular contents of polymorphonuclear eosinophils?
Major basic protein Eosinophil cationic protein Arysulfatase B Histaminase Phospholipase D Peroxidase Colligenase elastase platelet activating factor
What does the Major basic protein Do?
Parasite killing, neutralizes heparin
What does Eosinophil caitionic protein do?
Parasite killing
What is seen in serum as a result of parasite infection?
High levels of IgE and eosinophils
How do eosinophils suppress inflammation?
by destroying mast cell factors.
Activated eosiniphils produce and release?
lipid meadiators such as leukotrienes (LTC4,LTD4,LTE4)
Explain how TH2 cells, mast cell, IgE and Eosinophils interact to kill parasites via ADCC
Stiulation of TH2 cytokines from the helminth. IL-3 and IL-4 produced stimulate mucosal mast cell growth and IL-5 stimulates the development and activation of eosinophils. Fce receptors on eosinophils mediate eosinophil binding to the IgE bound parasite.
What proteins are found in the granules of eosinophils? what is their function?
Major basic protein- interacts with the negatively charged helminth membrane and is toxic to that helminth, eosinophil cationic protein= forms pores in helminth membrane.
List at lest 3 ways in which parasites avoid immune mechanisms. Pay specific attention to stage specific immunity.
Shedding of glycocalyx coat, camouflaging, antigenic variation (stage specific antigens, Continuous antigenic variation) etc.
Where are most antigens found in arthropods?
saliva
