MODULE 2 - HYPERSENSITIVITY | GUARANTEED
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Define hypersensitivity Answer: a normal but exaggerated or uncontrolled immune
response to an antigen that can produce inflammation, cell destruction or tissue injury.
Define Allergy Answer: any altered reaction to external substances
Define atopy Answer: refers to immediate hypersensitivity mediated by IgE antibodies
Define immunization/sensitization Answer: describes an immunological raction
dependent on the host's response to a subsequent exposure to antigen.
-small quantities of antigen may favor sensitization by restricting the antibody formed
What are the three categories of antigens? Answer: Type 1: Allergen
(ie. pollen, nuts, penicillin): Ags that can stimulate an IgE response
Type 2: Caused by IgG and IgM reaction with altered self antigens in the host
-involve antigens on the surface of cells or tissues (ABO blood typing)
Type 3: Soluble Ag and Ab immune complexes
What are hypersensitivity reactions ?
what are they dependent on?
what are they classified by? Answer: Immune reactions that are injurious to the host-
overactive immune system leading to tissue damage.
Reaction dependent on host's response, not the nature of Ag
Classified by the Gell and Coombs system
Hypersensitivity reactions:
Mediated by:
reaction:
type 1.
type 2.
type 3.
type 4. Answer: type 1:
IgE mediated
anaphylactic rxn
type 2:
IgG and IgM mediated
Cytotoxic rxn
type 3:
IgG and IgM mediated
immune complex rxn
type 4:
T- cell mediated
delayed hypersensitivity rxn
Gell and Coombs Classification of Hypersensitivity rxns:
Type 1:
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, - features?
- sample condition? Answer: Type 1:
features:
- IgE mediated
- mast cell degranulation
sample condition :
- asthma
-hay fever
Gell and Coombs Classification of Hypersensitivity rxns:
Type 2:
- features?
- sample condition? Answer: Type 2:
features:
- antibody mediated cell surface reactions that cause cytotoxicity, complement activation
sample condition:
- hemolytic anemia
- HDFN
Gell and Coombs Classification of Hypersensitivity rxns:
Type 3:
- features?
- sample condition? Answer: Type 3:
features:
- immune complex mediated, complement activation
sample condition:
- arthus reaction
Gell and Coombs Classification of Hypersensitivity rxns:
Type 4:
- features?
- sample condition? Answer: Type 4:
features:
- cell mediated, sensitized T cells, activate macrophages
sample condition:
- contact dermatitis
Time course of Type 1-4 hypersensitivity
type of reaction? Answer: Type 1: mediated by IgE
2-30 mins
- Intermediate type reaction-within 60 minutes after exposure
Type 2: antibody mediated cytotoxicity
5-8 hrs
Type 3: immune complex mediated
2-8 hrs
Type 4: cell mediated
24-72 hrs
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
SUCCESS STARTS HERE! LEARN, PRACTICE &
EXCEL!
Define hypersensitivity Answer: a normal but exaggerated or uncontrolled immune
response to an antigen that can produce inflammation, cell destruction or tissue injury.
Define Allergy Answer: any altered reaction to external substances
Define atopy Answer: refers to immediate hypersensitivity mediated by IgE antibodies
Define immunization/sensitization Answer: describes an immunological raction
dependent on the host's response to a subsequent exposure to antigen.
-small quantities of antigen may favor sensitization by restricting the antibody formed
What are the three categories of antigens? Answer: Type 1: Allergen
(ie. pollen, nuts, penicillin): Ags that can stimulate an IgE response
Type 2: Caused by IgG and IgM reaction with altered self antigens in the host
-involve antigens on the surface of cells or tissues (ABO blood typing)
Type 3: Soluble Ag and Ab immune complexes
What are hypersensitivity reactions ?
what are they dependent on?
what are they classified by? Answer: Immune reactions that are injurious to the host-
overactive immune system leading to tissue damage.
Reaction dependent on host's response, not the nature of Ag
Classified by the Gell and Coombs system
Hypersensitivity reactions:
Mediated by:
reaction:
type 1.
type 2.
type 3.
type 4. Answer: type 1:
IgE mediated
anaphylactic rxn
type 2:
IgG and IgM mediated
Cytotoxic rxn
type 3:
IgG and IgM mediated
immune complex rxn
type 4:
T- cell mediated
delayed hypersensitivity rxn
Gell and Coombs Classification of Hypersensitivity rxns:
Type 1:
APPHIA – Crafted with Care and Precision for Academic Excellence.
1
, - features?
- sample condition? Answer: Type 1:
features:
- IgE mediated
- mast cell degranulation
sample condition :
- asthma
-hay fever
Gell and Coombs Classification of Hypersensitivity rxns:
Type 2:
- features?
- sample condition? Answer: Type 2:
features:
- antibody mediated cell surface reactions that cause cytotoxicity, complement activation
sample condition:
- hemolytic anemia
- HDFN
Gell and Coombs Classification of Hypersensitivity rxns:
Type 3:
- features?
- sample condition? Answer: Type 3:
features:
- immune complex mediated, complement activation
sample condition:
- arthus reaction
Gell and Coombs Classification of Hypersensitivity rxns:
Type 4:
- features?
- sample condition? Answer: Type 4:
features:
- cell mediated, sensitized T cells, activate macrophages
sample condition:
- contact dermatitis
Time course of Type 1-4 hypersensitivity
type of reaction? Answer: Type 1: mediated by IgE
2-30 mins
- Intermediate type reaction-within 60 minutes after exposure
Type 2: antibody mediated cytotoxicity
5-8 hrs
Type 3: immune complex mediated
2-8 hrs
Type 4: cell mediated
24-72 hrs
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
