Question 1

What is the difference between anaphylactic and anaphylactoid reactions?

Accepted Answer

Anaphylactic reactions are mediated by IgE, while anaphylactoid reactions are mediated by complement or direct reaction with basophils and mast cells. Both may have life-threatening symptoms, and may be prevented if patients avoid known agents that cause these reactions, especially if they have had a previous serious reaction. However, neither is completely avoidable due to the potential for accidental exposure to agents that cause either reaction.

Question 2

What role does histamine play in allergic reactions?

Accepted Answer

Histamine is a granule component of mast cells and basophils. Histamine increases vascular permeability, which allows fluid to leak out of blood vessels and into tissue, causing the characteristic swelling associated with allergies.

Question 3

Which of the following is/are responsible for class switching to IgE production in allergic reactions? 
I. IL-5
II. IL-4
III. IL-13

Accepted Answer

IL-4 and IL-13 are the main cytokines that are responsible for antibody class switching to IgE production. The other main cytokine affecting allergic reactions is IL-5, which stimulates growth and activation of eosinophils.

Question 4

During an allergic reaction, IgE binds to Fc receptors on what cell types?

Accepted Answer

While many immune cells have Fc receptors, mast cells and basophils have Fc receptors that are specific for IgE. Binding of IgE causes release of granules that contain mediators of the allergic response, including histamine and heparin.

Question 5

The late phase of asthma mainly involves:

Accepted Answer

The early phase mainly involves bronchoconstriction caused by allergy-activated hyperresponsiveness of the airways, as well as the release of granules from mast cells and basophils. The late phase involves products that are synthesized and released from mast cells and basophils, including leukotrienes and prostaglandins that cause edema of the affected area.

Question 6

The radioallergosorbent (RAST) assay is used to test which individuals for allergies?

Accepted Answer

Individuals get a RAST, which is a laboratory test and not a skin test, when they are at risk for having an anaphylactic reaction during a skin test.

Question 7

Oral allergy syndrome is caused by:

Accepted Answer

Oral allergy syndrome occurs in individuals who are sensitive to pollen, and then eat fruits or vegetables that have shared antigens with pollen. This exposure leads to burning or pruritus of the lips, tongue, and edema of the buccal mucosa.

Question 8

Hyposensitization therapy results in the production of:

Accepted Answer

Administration of small amounts of allergen to an allergic individual results in the production of IgG specific for that allergen. IgG coats the allergen and blocks IgE from binding to the allergen, thus preventing the allergic reaction from proceeding.

Question 9

Which of the following could be a potential outcome of an allergy-induced increase in vascular permeability? 
I. Edema
II. Hypovolemic shock
III. Smooth muscle contraction

Accepted Answer

The increase in vascular permeability leads to fluid leaking out of the vessels and into the tissue, causing edema. In cases of anaphylaxis, the fluid leaves the vessels so rapidly that it can cause hypovolemic shock and death. While smooth muscle contraction may occur in allergic reactions, such as asthma, it does not always occur, and is not related to an increase in vascular permeability.

Question 10

Which of the following is a true allergic reaction? 
I. Latex allergy
II. Cockroach allergy
III. Radiocontrast media allergy

Accepted Answer

Reactions to latex products and cockroaches are True allergic reactions, while reactions to radiocontrast media are anaphylactoid reactions.

Quiz 15: Immediate Allergic Reactions