Lecture 14 - Immunoparasitology Flashcards
What is the only parasite with a vaccine
malaria
What are common parasites to alberta
- cryptosporidium
- giardia
- toxoplasma
- amoebiasis
- enterobius
- tapeworms
- roundworms
Ectoparasite
- lives on the outer surface of the host
Endoparasite
- lives inside the body of the host
Obligate parasite
- completely dependent on the host during part or all of its life cycle
Facultative parasite
exhibits both parasitic and free living stages
Accidental parasite
infects an unnatural host and survives
Erratic parasite
migrates improperly and ends up in host tissue where it is not usually found
What are the direct impacts of parasites on the host
- mechanical injury
- production of toxic substances
- nutrient depravation
-anemia
What are the indirect impacts of parasites on the host
- inflammation
- encapsulation
- reduced cognitive capability
What occurs during initial exposure to a parasite
- parasite must arrive safely before infection can begin
- complement is important at this stage
- many parasites have molecules on their surface that can activate the alternative pathway
- previous exposure may have resulted in circulating antibodies
- if moving through tissues or blood the parasite will encounter some immune cells
What occurs during the establishment stage of a parasite infection
- parasite implements immunomodulatory programs and continues to avoid detection
- depending on location in the host the parasite may encounter various immune effectors
– tissues: cellular defense and inflammation
– blood: cellular defense, antibody, circulating defense molecules, complement
– gastrointestinal: IgA, antimicrobial peptides, physical environment
What occurs during the chronic infection of a parasite
- usually immune evasion is working now
- immune response unlikely to kill it
- immune response becomes tolerant
What do neutrophils do during parasitic infections
- reactive oxygen/nitrogen production
- granules released have cytotoxic proteins
– primary granules: myeloperoxidase, bacteriacidal, defensins, elastase
– secondary granules: alkaline phosphatase, lysozyme, collagneases
– tertiary granules
What do eosinophils due during parasitic infections
- characteristically associated with worm infections
- degranulate when surface Fc receptors recognize IgE
- often act in concert with MAST cells because of IgE detection
How does phagocytosis occur
- tissue macrophages, monocytes and granulocytes have basal defense capacity that can be engaged before any cytokine production or antibody response is generated
- phagocytic cells remove protozoans and encapsulate small multicellular parasites (can engulf targets many times their size due to recruitment of membrane from the ER and cytoplasmic vesicles)
- phagocytosis can result in inflammation and production of cytokines that regulate the subsequent immune response
How does inflammation occur
production and release of reactive oxygen and nitrogen species as well as cytokines initiate a signalling cascade leading to the activation of immune cells and production of further general anti-pathogen effectors
How do things transition from innate to adaptive immunity during parasitic infection
phagocytosis facilitates the breakdown of pathogen material so it can be present through MHCII to t-cell receptors on CD4+ cells of the adaptive response
What is IgE
- the least common serum antibody
- high affinity to the Fc receptors of: mast cells, basophils, eosinophils
- does not bind complement
What is the main function of IgE
- immunity to helminth parasites
- plays a role in immunity to protozoan parasites such as Plasmodium spp
- associated with allergy and hypersensitivity
What cell is critical for proper defense against helminths
MAST cells
What do MAST cells do when triggered
degranulate producing:
- serine proteases
- histamine
- serotonin
- anticoagulants
- platelet activating factor
- cytokines
- eosinophil chemotactic factor
What do MAST cell triggering cause
extensive swelling, vasodilation, inflammation and pain or itching
What is antibody dependent cell-mediated cytotoxicity
- innate effector cells recognize antigen-bound antibodies on the surface of a parasite
- usually mediated through recognition of the Fc portion of an antibody by a cell-surface Fc receptor to IgG or IgE
- results in cytokine release that promotes apoptosis in the target cell
- particularly important for defense against larger helminth parasites that are too large for phagocytosis
