Hypersensitivity Reactions Flashcards
(31 cards)
hypersensitivity reaction
an immune reaction to foreign or self antigens that are excessive and harmful
What mediates type I hypersensitivities?
IgE
What mediates type II hypersensitivities?
IgG mediated cytotoxic hypersensitivity
What mediates type III hypersensitivities?
immune complex-mediated hypersensitivity
What mediates type IV hypersensitivities?
cell-mediated hypersensitivities
what type of hypersensitivity is asthma?
type I
what type of hypersensitivity are seasonal allergies?
type I
what type of hypersensitivity is a food allergy?
type I
what type of hypersensitivity is severe allergic reaction? What are components?
Type I: uticaria (hives), angioedema, anaphylaxis
what does IL-4 do?
class switching to IgE
what does IL-5 do?
eosinophil activation
what does IL-13 do?
enhanced IgE production
How are mast cells activated in type I hypersensitivities?
mast cells bind IgE to their FCεRI receptor
What mediates the immediate hypersensitivity reaction seen with type 1 hypersensitivities?
vasoactive amines and lipid mediators
* minutes after repeat exposure to allergen
What mediates the late phase hypersensitivity reaction seen with type 1 hypersensitivities?
cytokines
* 2-24 hours after repeat exposure to allergen
what is seen with mast cell activation?
1) degranulation leads to histamine release
2) lipid mediators like leukotrienes B4/C4/D4, prostaglandin D2, and platelet activating factor
3) cytokines and chemokines recruit leukocytes in late phase
what is the physiologic immediate response in type I hypersensitivities?
vasodilation, vascular leakage, smooth muscle spasm
what is the physiologic late phase response in type I hypersensitivities?
leukocyte infiltration, epithelial damage, bronchospasm
eosinophils, basophils, neutrophils
what type of hypersensivity is eosinophilic esophagitis?
type 1
What is eosinophilic esophagitis?
- late phase type I hypersensitivity
- dense infiltrate of inflammatory cells
- food antigen-driven disease of childhood
- recurrent dysphagia
- weight loss (can’t swallow effectively, hurts to swallow)
Treat type I hypersensitivity allergic reaction
block histamine and airway support
Steps in skin prick allergy test
1) IgE from previous exposure bound to mast cells
2) injected allergen binds to IgE molecules
3) IgE cross-liking activates mast cells
4) vasodilation, increased interendothelial spaces: redness and swelling
type II hypersensitivity reaction
reactions where antibodies directly react with antigens present on the cell surface or extracellular matrix (autoantibodies or exogenous antigens that are bound to cell surfaces)
3 mechanisms type II hypersensitivity reactions
1) opsonization and phagocytosis
2) complement and FC receptor-mediated inflammation
3) antibody-mediated cellular dysfunction
