Hypersensitivities

Question 1

What is a hypersensitivity?

Answer 1

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

Question 2

Describe the first stage of a hypersensitivity.

Answer 2

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.

Question 3

Describe the second stage of a hypersensitivity.

Answer 3

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

Question 4

Quickly differentiate the four hypersensitivities.

Answer 4

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

Question 5

Define allergy

Answer 5

Hypersensitivity to a foreign, environmental antigen.

Question 6

Define atopy

Answer 6

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

Question 7

Discuss Type 1 hypersensitivity

Answer 7

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)

Question 8

Discuss Mast cell secretions

Answer 8

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

Question 9

Describe the pathology of Allergic rhinitis/ Hay fever.

Answer 9

Increased mucus secretion; inflammation of upper airways and sinuses.

Question 10

Describe the pathology of food allergies.

Answer 10

Increased peristalsis due to contraction of intestinal muscles.

Question 11

Describe the pathology of bronchial asthma

Answer 11

Airway obstruction caused by smooth muscle hyperactivity.

Question 12

Describe the pathology of anaphylaxis

Answer 12

Drop in bp caused by vascular dilation; laryngeal edema.

Question 13

Describe the pathology of allergic uticaria (hives)

Answer 13

Vasodilation and vascular permeability; Prurutis

Question 14

Discuss anaphylatic shock

Answer 14

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

Question 15

Discuss anaphylatoid shock

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Discuss the hygiene hypothesis.

Answer 17

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