Question 1

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Protein constituent of granules that contributes to tissue damage in immediate hypersensitivity reactions

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Tryptase is a neutral serine protease stored in mast cell granules
When released into the extracellular matrix, this enzyme cleaves fibrinogen and activates collagenases, contributing to tissue damage.

Question 2

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Lipoxygenase-pathway product of arachidonic acid metabolism that causes prolonged bronchoconstriction, mucus secretion, and increased vascular permeability

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Leukotriene C₄ (LTC₄) is rapidly synthesized by the lipoxygenase pathway of arachidonic acid metabolism in activated mast cells
It is one component of a so-called slow-reacting substance of anaphylaxis, which also includes LTD₄ and LTE₄
These leukotrienes are major mediators of bronchoconstriction in allergic asthma.

Question 3

Which of the following is the most common disorder of immunity that affects 20% of all individuals in the United States?&#10;A) Atopy&#10;B) Diabetes mellitus&#10;C) Leukemia&#10;D) IgA deficiency&#10;E) Latent tuberculosis infection

Accepted Answer

Atopy, or allergy, is the most common disorder of immunity and affects 20% of all individuals in the United States
Within this category, allergic rhinitis is perhaps the most common allergic disease and is a consequence of immediate hypersensitivity reactions to common allergens, such as plant pollen or house dust mites, localized to the upper respiratory tract by inhalation
Selective IgA deficiency is the most common known primary immunodeficiency.

Question 4

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Biogenic amine that transiently increases vascular permeability and smooth muscle contraction

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Histamine, one of several biogenic amines in mast cell granules, is partly responsible for the rapid increases in vascular permeability causing wheals (or hives) and for the smooth muscle contraction in bronchi and intestines, causing some of the pulmonary and gastrointestinal symptoms of immediate hypersensitivity reactions.

Question 5

All of the following are key mediators of immediate hypersensitivity reactions EXCEPT:&#10;A) Mast cells&#10;B) Basophils&#10;C) IgE&#10;D) Macrophages&#10;E) TH2 cells

Accepted Answer

The main cellular mediators of immediate hypersensitivity reactions are mast cells, basophils, and eosinophils
IgE antibody plays a major role in sensitizing these cellular mediators for subsequent activation
Activation of TH2 cells is required for appropriate release of cytokines, such as interleukin (IL)-4 and IL-13, which stimulate IgE class switching in B cells
In contrast, macrophages are effector cells in delayed-type hypersensitivity reactions.

Question 6

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Cyclooxygenase-pathway product of arachidonic acid metabolism that causes vascular dilatation, smooth muscle contraction, and neutrophil chemotaxis

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Prostaglandin D₂ (PGD₂) is the major arachidonic acid product of the cyclooxygenase pathway in mast cells
PGD₂ causes vasodilation and bronchoconstriction, which contribute to the early signs and symptoms of immediate hypersensitivity reactions
It also is a chemoattractant for neutrophils, which accumulate in tissues as part of the late-phase inflammatory response to allergens.

Question 7

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Soluble factor that promotes eosinophil maturation and activation

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Interleukin-5 is a cytokine synthesized by activated mast cells (as well as TH2 cells) and promotes eosinophilia and eosinophilic inflammation, which are characteristic of chronic immediate hypersensitivity conditions.

Question 8

Immediate hypersensitivity differs from delayed-type hypersensitivity in which one of the following ways? A) Immediate hypersensitivity is a CD4⁺ T cell-mediated disease. B) Immediate hypersensitivity does not require previous exposure to an antigen. C) Immediate hypersensitivity does not involve inflammation. D) Immediate hypersensitivity is driven by cytokines such as interleukin (IL)-4, IL-5, and IL-13. E) Immediate hypersensitivity typically leads to granuloma formation.

Accepted Answer

In contrast to delayed-type hypersensitivity (DTH), which is a TH1-mediated disorder, immediate hypersensitivity is driven by cytokines, such as interleukin (IL)-4, IL-5, and IL-13, and is therefore a TH2-mediated disorder
Note that both types of hypersensitivity reactions involve CD4⁺ T cells (TH1 vs
TH2), although DTH also involves CD8⁺ T cells
Importantly, both types of hypersensitivity reactions occur only after prior exposure to an antigen, and they are both characterized by inflammation
Granuloma formation, as a chronic response to persistent microbes, is a pathologic feature more typical of DTH than immediate hypersensitivity.

Question 9

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Soluble factor that promotes inflammation and late-phase reaction and activates endothelial expression of adhesion molecules critical for sequential neutrophilic infiltrate

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

When tumor necrosis factor-a is released during IgE-mediated mast cell activation, it activates endothelial expression of the adhesion molecules, accounting for subsequent infiltration of neutrophils
As such, it is critical for inflammation and the late-phase allergic reaction.

Question 10

Matching
Match the definitions in questions with the mast cell mediator (A-G) that most closely matches it.
Membrane phospholipid derivative that causes bronchoconstriction, retraction of endothelial cells, and relaxation of vascular smooth muscle

A)Histamine
B)Tryptase
C)Prostaglandin D₂
D)Leukotriene C₄
E)Platelet-activating factor
F)Interleukin-5
G)Tumor necrosis factor-a

Accepted Answer

Platelet-activating factor (PAF) is synthesized after mast cell activation by acylation of a membrane phospholipid derivative; it acts on bronchial smooth muscle cells and endothelial cells
Genetic deficiency of an enzyme that inactivates PAF is associated with asthma.

Deck 14: Immediate Hypersensitivity