Hypersensitivity Flashcards
What are hypersensitivities?
inappropriately vigorous host immune response to antigen
What are the four types of hypersensitivities?
Type I = anaphylaxis
Type II = Antibody-mediated cytotoxicity
Type III = Immune complex disease
Type IV = Delayed hypersensitivity
What is a type I hypersensitivity? How is it brought about?
Anaphylaxis - brought about by antigen binding to the surface of IgE-coated basophils or mast cells, causing release of histamine
How fast is a type I hypersensitivity?
Very fast
Seasonal allergies are what type of hypersensitivity?
Type I (IgE mediated)
What does it mean for an individual to be atopic?
those that have an increased tendency to develop allergies
IgE is mostly made to fend off against what type of antigen? What is its role in anaphylaxis?
Made for parasites, but released in response to allergens in atopic individuals
What is the default pathway in the absence of inflammation: Th1 or Th2? What is the significance of this in anaphylaxis?
Th2– IgE production is the outcome of the lack of inflammation as seen in anaphylaxis
What is the “hygiene hypothesis”?
decreased exposure to pathogens early in life (which would favor the development of Th1-mediated immune responses), leading to the development of strong Th2-mediated immunity and subsequent IgE production
What are most respiratory allergens?
small molecules that are carried on larger particles such as pollen grains or mite feces
What sort of delivery method to the body do most respiratory allergens go through? What does this elicit?
Transmucosal delivery, causes Th2 IgE responses
Physiologic responses to parasites usually occur where?
Skin, airways, gut
What are basophils?
Granulocytes withgranules present in cytoplasm
Where are basophilis usually found?
Peripheral blood
Are basophils phagocytic?
Negative
How are basophils related to mast cells?
Similar, but arise from different cells
Where are mast cells usually located?
Near small blood vessels and post capillary venules in mucosal tissues
What is on the surface of mast cells that binds to IgE released during anaphylaxis? Binding to this area causes what?
Fc receptors–binding = histamine release and degranulation
How do anaphylatic reactions come about (what leads to hypersensitivity)?
1st exposure stimulates IgE production. Subsequent exposure to the allergen binds to the surface bound IgE and activates the cells to release their granule contents.
What are the two major chemicals in mast cells that mediate anaphylaxis?
Histamine, TNF-alpha
How does the amount of eosinophils in allergic individuals compare to that of non-allergy prone people?
Higher
What are the four major Leukotrienes, and what are their effects?
LTC4, LTD4, and LTE4.
Most potent substances known that cause smooth muscle contraction and increased vascula rpermeability
How long does it take leukotrienes to be synthesized? How do they compare to histamine?
Released more slowly than histamine, but have a longer effect
Where do eosinophils accumulate?
Nasal and bronchial mucosa in respiratory allergies, and in intestinal mucosa during certain worm infections