Type I Hypersensitivity Reactions Flashcards
What are Hypersensitivity reactions?
Immune reactions that are excessive or harmful
How many types of Hypersensitivity reactions are there?
4 (I-IV)
When will you recognize Type I reactions?
ON SIGHT
What are the most common Type I reactions?
Seasonal and Food Allergies
Asthma
Anaphylaxis, Angioedema, Hives (urticaria)
What are the most common Type I reactions?
Seasonal and Food Allergies
Asthma
Anaphylaxis, Angioedema, Hives (urticaria)
Describe the setup before a Type I reaction will take place
- DCs present Ag to naive T cells
- T cells differentiate into Th2 cells
- Th2 cells cause the B cells to switch to IgE
- Mast cells prepare by binding IgE to their FcER1
For a Type I reaction, what occurs after the DC presents the Antigen to a naive T cell?
T cell turns into a Th2 cell
For a Type I reaction, what occurs after a Th2 cell is created?
B cells class switch to IgE
For a Type I reaction, what occurs after IgE is made?
Mast cells bind IgE to their receptor FcER1
What cytokine helps B cells class switch to IgE?
IL-4
What cytokine helps enhance IgE production?
IL-13
What cytokine activates Eosinophils?
IL-5
What occurs for a Type I reaction to take place?
REPEAT EXPOSURE TO ANTIGEN
What occurs upon repeat exposure to the antigen?
Mast cells degranulate
The immediate reaction for Type I occurs in minutes. What is specifically released from the mast cells in this phase?
Histamine
Leukotrienes (B4, C4, D4)
Prostaglandin D2
Platelet Activating factor
Result of the immediate reaction for Type I?
Vasodilation and Increased vascular permeability
Smooth muscle contraction
The immediate reaction for Type I occurs in minutes. What is specifically released from the mast cells in this phase?
Histamine
Leukotrienes (B4, C4, D4)
Prostaglandin D2
Platelet Activating factor
The late phase for Type I occurs 2-24 hours after initial exposure. What is specifically released from the mast cells in this phase?
Cytokines and chemokines
When cytokines and chemokines are released during the late phase, what do they do?
Recruit leukocytes - eosinophils, basophils, neutrophils
When cytokines and chemokines are released during the late phase, what do they do?
Recruit leukocytes - eosinophils, basophils, neutrophils
Result of the late phase for Type I?
Epithelial damage
Bronchospasm
What causes Eosinophilic Esophagitis?
Food antigens
Symptoms and age group of those affected with Eosinophilic Esophagitis?
Children
= Dysphagia, weight loss, hurts to swallow
Treatment cascade for Type I reactions?
Diagnose that a reaction is occurring
Treat - block histamine or airway support
Identify allergen
Describe the skin-prick test
- Inject allergen
- IgE that is bound to mast cells binds allergen
- IgE cross links to activate mast cells
= Vasodilation and increased permeability
= = Redness and swelling at site of injection
