Immediate hypersensitivity Flashcards
1
Q
why do some individuals preferentially make IgE antibodies>
A
- reason is unclear
- genetic component
- mode of administration of antigen (skin or mucous mem favor IgE)
- APC preferentially actiave TH2 cells resulting in the production of IL4 and IL3
- failure of control of TH2 cells
2
Q
activation of TH2 cells in IgE production
A
- APC presents and B7 binds to CD28
- IL2 is produced and interacts with IL2 receptor
- TH2 proliferates making more TH2
- TH2 cells release IL3 and 4 which interact with B cells causing release of IgE
3
Q
what does an IgE do
A
- binds to mast cells via the Fc receptor
- when antigen binds, it causes the mast cell to degranulate
- acute release of granules cause allergic rhinitis (hay fever)
4
Q
early phase mediators released by mast cells and basophils
A
- histamine
- protease
- leukotriennes
- prostaglandins
- platelet activating factor
- chemotactic factors for neutrophils and eosinophils
5
Q
late phase mediators released in the laste phase of the acute allergic response
A
- these are cytokines released from mast cells, TH2, macrophages, and eosinophils
- this phase can be controlled by corticosteroids that inhibit cytokine production
6
Q
examples of IgE mediated allergic reaction
A
- hay fever, allergic rhinitis
- bronchial asthma - bronchial constriction
- acute drug reactions
- food allergy
- insect stings
- acute urticaria (hives)
7
Q
diagnosis of acute allergic diseases
A
- skin prick tests (intradermal), positive will flare in 5-10 mins
- measure specific IgE antibodies to an antigen, this is often the RAST test
8
Q
treatment of type 1 allergic reactions
A
- epi used to treat acute anaphylactic reactions
- remove the antigen
- treat symptomatically with antihistamines, anti-leukotrienes, corticosteroids
- omalizumab (monoclonal antibody that inhibits IgE binding to mast cells)
- hyposensitization therapy (shots)
9
Q
hyposensitization (desensitization)
- what do you do
- what happens
- why does it happen
A
- consists of multiple exposures to increasing concentrations of the antigen.
- results in an increase of IgG antibodies
- if untreated, the body eracts with low IgG and high IgE
- after a while the IgG will pass the IgE and the IgE will go down
- could activate the Th1 cells or activate TREG cells to inhibit Th2 cells
10
Q
what other mechanisms can degranulate mast cells other than IgE?
A
- C5a and C3a (anaphylatoxins)
- heat
- cold
- pressure
- exercise
- CNA effects via the vagus nerve
- direct effect of drugs on mast cells
