Whats an Allergic Reaction / Hypersensitivity?
a response to Ags not associated with infectious agents
what is the first exposure to an allergen? What happens?
sensitization (IgE production)
What is the second exposure to an allergen? What happens?
effector reaction (activation of IgE binding cells)
What is Atropy?
predisposition to become IgE-sensitized.
What type of hypersensitivity reaction is immediate?
type 1
What type of hypersensitivity reaction is cytotoxic?
type 2
What type of hypersensitivity reaction is with an immune complex?
type 3
What type of hypersensitivity reaction is delayed?
type 4
What type of hypersensitivity reaction(s) is antibody mediated?
type 1, type 2, and type 3
What type of hypersensitivity reaction(s) is T cell mediated?
type 4
What type of hypersensitivity reaction(s) is IgE mediated?
type 1
What type of hypersensitivity reaction(s) is IgG mediated?
type 2 and type 3
What type of hypersensitivity reaction is IgG and IgE mediated?
type 2
____ are the most common sensitizing agents.
proteases
What are types of Type 1 reactions? (2)
- wheal and flare (swelling and redness)
- anaphylaxis (antigen travels through blood for systematic response)
being in a clean environment causes ____ risk of sensitization
increases
what is atopic march?
the progression of atopic conditions overtime
Type 1 hypersensitivities are treated with…
prednizone, benadryl, claritin, etc.
What are types of Type 2 reactions (3)
- phagocytosis
- compliment activation
- antibody-mediated cytotoxicity
How does a type 2 reaction occur?
when IgG recognizes surafce molecules and binds to destroy them.
how does a type 3 reaction occur?
IgG antibodies form a immune complex with the antigen, which activates compliment system. C5a binds to its receptor on mast cells to elicit an immune response.
what does a type 4 reaction occur?
T cell recognizes antigen, and releases cytokines for phagocytic recruitment.
what are the main two cytokines in type 4 reactions?
IFN-γ, TNF-α, and LT
describe the effector mechanism of sensitization.
FIRST EXPOSURE:
- allergen (ex. der p 1) is uptaken by dendritic cell, and presented to a T cell.
- t cell releases cytokines when result in a switch in plasma cells from IgG to IgE production.
- IgE binds to FcεRI on mast cells.
SECOND EXPOSURE:
- IgE produced binds to IgE-FcεRI (cross-linking)
- mast cell response (degranulation) begins.
