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Discussion Starter · #1 ·
A patient's signs and symptoms are mediated by antigen specific IgE antibody attached to high affinity receptors on surface of mast cells. by which of the following mechanisms does mast cell degranulate?

A- antibody receptor dissociation
B- antibody receptor covalent binding
C- receptor internalization
D- receptor aggregation
E- receptor detachment from cell surface

write not only the correct choice and its explanation, also give example's for rest of options.
 

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the answer is D

Aggregation of antigens and binding of IgE to the FcεRI on mast cells causes degranulation and the release of mediators from the cells, while basophils cross-linked with IgE release type 2 cytokines like interleukin-4 (IL-4) and interleukin-13 (IL-13) and other inflammatory mediators.
 

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answer is D (IgEFc receptor aggregation)

A patient's signs and symptoms are mediated by antigen specific IgE antibody attached to high affinity receptors on surface of mast cells. by which of the following mechanisms does mast cell degranulate?

A- antibody receptor dissociation
B- antibody receptor covalent binding
C- receptor internalization
D- receptor aggregation
E- receptor detachment from cell surface

write not only the correct choice and its explanation, also give example's for rest of options.
answer is D (IgEFc receptor aggregation)
 

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Discussion Starter · #12 ·
Can someone please explain what does "antigen cross-linking with antibody" means? Is it the aggregation of antibodies with antigens?
on first exosure IgE is produced as a response to allergen,it is released in serum and it binds to mast cell Fc receptor.
now remember many IgE antibodies are bound to mast cell and while in serum they have short half life but once bound to mast cell it can survive for years.

so next time when exposure occurs ALLERGEN will cross link several IgE molecules on mast cell-this is the step that will lead to mast cell degranulation.
 
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