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Flashcards in Hypersensitivities Deck (17):

What is a hypersensitivity?

Immune response against an antingen that we shouldn't react to; Unwanted/Uncontrolled response.


Describe the first stage of a hypersensitivity.

Occurs following the first exposure to the antigen; NO tissue injury. Antibodies are produced and circulate in the blood/lymph and bind to Fc receptors on mast cells and eosinophils. Can make memory T cells.


Describe the second stage of a hypersensitivity.

Occurs during the second or prolonged exposure to the antigen; Tissue injury.


Quickly differentiate the four hypersensitivities.

Type 1: Mast cells/Eosinophils degranulate
Type 2: Antibodies attach to cells or structures and fix complement.
Type 3: Immune complexes deposit and fix complement.
Type 4: Effector and memory T cell responses


Define allergy

Hypersensitivity to a foreign, environmental antigen.


Define atopy

A heritable predispostion to produce IgE and allergen specific T cells following exposure to allergens.


Discuss Type 1 hypersensitivity

Sensitization phase: Th2 causes Isotype switching to IgE, IL-4 and 5 secretion.
Elicitation phase: Cross linking with antigen, Mast cell degranulation (Histamine, Serotonin, PGs, Leukotrienes), then cytokine release (TNF-a, IL-1)


Discuss Mast cell secretions

1. Histamine (Granule): Blood vessel dilation
2. Proteases (Granule): Tissue damage
3. Prostaglandins (CM): Vasodilation
4. Leukotrienes (CM): Prolonged smooth muscle contraction
5. Cytokines (Transcription): Inflammation, chemotaxis


Describe the pathology of Allergic rhinitis/ Hay fever.

Increased mucus secretion; inflammation of upper airways and sinuses.


Describe the pathology of food allergies.

Increased peristalsis due to contraction of intestinal muscles.


Describe the pathology of bronchial asthma

Airway obstruction caused by smooth muscle hyperactivity.


Describe the pathology of anaphylaxis

Drop in bp caused by vascular dilation; laryngeal edema.


Describe the pathology of allergic uticaria (hives)

Vasodilation and vascular permeability; Prurutis


Discuss anaphylatic shock

Caused by allergens binding o IgE on mast cells/eosinophils, leading to systemic mast cell/eosinophil activation.


Discuss anaphylatoid shock

Systemic mast cell activation via ligands binding to receptors other than FceR. Can happen on first exposure.


What are the 3 goals of treatment for type 1 hypersensitivity?

1. Inhibit mast cell degranulation
2. Oppose effects of lipid mediators
3. Decrease inflammation


Discuss the hygiene hypothesis.

Increased exposure to pathogens early in life decreases the likelihood of developing allergies.