Hypersensitivity Flashcards
What is hypersensitivity?
Exaggerated or inappropriate immune response
What 3 things can hypersensitivity lead to?
- Tissue damage
- Serious disease
- Death
Give an example of hypersensitivity reactions
Anaphylaxis
What is angioedema in anaphylaxis?
A person is unable to breathe so oxygen has to be provided by a tube
Name 4 types of hypersensitivity reactions?
- Type I - IgE mediated
- Type II - Cytolytic or cytotoxic
- Type III - Immune complex
- Type IV - Cell mediated immunity
What are 2 main differences between type 1, type 2 and type 3 hypersensitivity reactions and type 4 hypersensitivity reactions?
- Type 1, type 2 and type 3 hypersensitivity reactions are mediated by antibodies and type 4 hypersensitivity reactions are mediated by T-cells
- Type 1, type 2 and type 3 hypersensitivity reactions are immediate and type 4 hypersensitivity reactions are delayed
What are the 3 phases of Type I Hypersensitivity?
- Sensitisation
- Activation
- Effector
What occurs during the sensitisation phase of Type I Hypersensitivity?
- Exposure to allergen activated Th2 cells which stimulate B cells to form IgE producing plasma cells
- IgE produced binds to Fc receptors on mast cells and basophils
What occurs during the activation phase of Type I Hypersensitivity?
Re-exposure to antigen triggers mast cells and basophils to response by release of granules
What occurs during the effector phase of Type I Hypersensitivity?
Complex response occurs as a result of histamine and other active agents released by mast cells and basophils
What are 5 effects of the effector phase on the body during Type I Hypersensitivity?
- Contraction of bronchial smooth muscles
- Increase mucus secretion
- Increased permeability of venules due to contraction of endothelial cells
- Vasodilation
- Stimulation of nerve endings
Name 3 physical expressions of effectors during Type I Hypersensitivity
- Airways obstructed
- Drop in blood pressure
- Cough
How quickly does Type I Hypersensitivity occur from exposure?
Immediate
Name 4 examples of localised Type I Hypersensitivity
- Hay fever (allergic rhinitis)
- Food allergy
- Atopic dermatitis
- Asthma
What is systemic anaphylaxis?
Shock-like and often fatal state initiated by an allergen introduced into the blood or absorbed by the gut or skin
Name 4 things which can cause systemic anaphylaxis
- Nuts
- Insulin
- Seafood
- Venom from bees, wasps or ants