Question 1

An example of a condition that involves type III hypersensitivity is:

Accepted Answer

Type III hypersensitivity involves the formation of immune complexes that deposit in tissues, leading to complement activation and inflammation. Rheumatoid arthritis is an autoimmune condition in which immune complexes deposit in the joints, causing inflammation and tissue damage. Myasthenia gravis (A) is a type II hypersensitivity, allergic rhinitis (B) is a type I hypersensitivity, and contact sensitivity (C) is a type IV hypersensitivity.

Question 2

The precipitation of immune complexes in small blood vessels under the skin that occurs when antigen is injected in an animal with large amounts of circulating antibody describes which of the following?

Accepted Answer

The description matches the definition of Arthus reaction. Serum sickness involves an immune response to an administered foreign serum or protein, anaphylaxis typically involves a sudden and severe allergic reaction, and delayed hypersensitivity occurs when T cells react to antigen and release cytokines causing inflammation.

Question 3

The principal difference between type II and type III hypersensitivity reactions is:

Accepted Answer

The principal difference between type II and type III hypersensitivity reactions is based on the nature of the antigen involved. In type II hypersensitivity reactions, the antigen is usually present on the surface of host cells or tissues, leading to complement-mediated lysis of those cells by antibodies. In contrast, in type III hypersensitivity reactions, the antigen is usually soluble and forms immune complexes with antibodies, which can deposit in host tissues and cause inflammation and tissue damage. The isotype of the antibody involved and the involvement of helper T cells and macrophages are not specific differences between these two types of hypersensitivity reactions.

Question 4

What immune phenomenon is responsible for the muscle weakness associated with myasthenia gravis?

Accepted Answer

Myasthenia gravis is an autoimmune disease in which antibodies bind to acetylcholine receptors on muscle cells, leading to decreased muscle function and weakness. This antibody binding disrupts the normal transmission of nerve impulses to the muscles, resulting in muscle weakness and fatigue.

Question 5

Reaction to poison ivy is which type of hypersensitivity?

Accepted Answer

Poison ivy reaction is a delayed hypersensitivity reaction, also known as type IV hypersensitivity. This type of hypersensitivity involves the activation of T cells, which release cytokines that lead to the recruitment of inflammatory cells causing the rash and itching.

Question 6

A hypersensitivity reaction characterized by the presence of IgG that reacts with soluble antigen best describes:

Accepted Answer

Type III hypersensitivity, also known as immune complex-mediated hypersensitivity, involves the deposition of circulating antigen-antibody complexes in tissues and subsequent activation of complement and inflammatory mediators. This results in tissue damage and inflammation.

Question 7

Anaphylactic reactions are mediated by:

Accepted Answer

Anaphylactic reactions are mediated by mast cells. Mast cells release various mediators, such as histamine, prostaglandins, and leukotrienes, which cause the symptoms of anaphylaxis.

Question 8

A 5-year-old girl was rushed to the emergency department because she was having trouble breathing.She had been playing at the park when she fell down and her face and neck started to swell up.One of her friends thought that the girl might have been stung by a bee because a bee was flying around them,and shortly before the girl fell to the ground,she had screamed.The girl had a large red bump on her cheek.This girl likely has:

Accepted Answer

The girl's symptoms suggest that she is experiencing a type I hypersensitivity reaction, also known as an allergic reaction, which occurs when the body overreacts to a harmless substance known as an allergen. In this case, the bee sting likely caused the girl's immune system to release histamine and other chemicals, leading to the swelling and difficulty breathing. Bruton's hypogammaglobulinemia and type I diabetes would not typically cause symptoms like swelling and difficulty breathing in response to a bee sting. Type IV hypersensitivity reactions typically take longer to develop and involve different immune cells than type I reactions.

Question 9

Preformed mediators that are released during the activation phase of a type I hypersensitivity response include which of the following?

Accepted Answer

Histamine is a preformed mediator stored in mast cells and basophils, which is released during the activation phase of a type I hypersensitivity response, leading to symptoms such as itching, swelling, and vasodilation.

Question 10

Reactions to antigens in natural rubber (latex)can trigger:

Accepted Answer

Reactions to antigens in natural rubber (latex) typically trigger both type I (immediate hypersensitivity) and type IV (delayed hypersensitivity) reactions. Type II and III hypersensitivity reactions are not commonly associated with latex allergy.

Question 11

All of the hypersensitivity responses have which of the following in common?

Accepted Answer

All hypersensitivity responses involve an asymptomatic sensitization phase, where the immune system is first exposed to the allergen without an overt allergic reaction. This phase is crucial for the development of the hypersensitivity response upon subsequent exposures.

Question 12

Which of the following diseases is an example of a type II hypersensitivity?

Accepted Answer

Myasthenia gravis is an autoimmune disease where autoantibodies bind to and inactivate acetylcholine receptors at neuromuscular junctions, leading to muscle weakness. This is an example of a type II hypersensitivity reaction, where antibodies target self-antigens on the body's own cells. Anaphylaxis (A) is a type I hypersensitivity reaction involving IgE antibodies and immediate allergic reactions. Post-streptococcal glomerulonephritis (C) is a type III hypersensitivity reaction where immune complexes form and deposit in the kidneys, leading to inflammation and damage. Bruton's agammaglobulinemia (D) is a primary immunodeficiency where individuals have insufficient levels of antibodies and are unable to mount an effective immune response against infections.

Question 13

Hypersensitivities to poison ivy and nickel are:

Accepted Answer

Hypersensitivities to poison ivy and nickel are examples of Type IV hypersensitivity reactions, which are mediated by T cells and macrophages rather than antibodies. This type of reaction involves a response to a hapten, which is a small molecule that can elicit an immune response only when attached to a large carrier such as a protein; the process does not involve IgG, IgM, or IgE antibodies directly.

Question 14

Type I hypersensitivity can be treated by injecting a specific recombinant humanized IgG called omalizumab.This antibody:

Accepted Answer

Omalizumab works by binding to the Cε3 domain on the heavy chain of IgE. This prevents IgE from binding to its high-affinity receptor (FcεRI) on the surface of mast cells and basophils, thus inhibiting the allergic response.

Question 15

The normal activity of a type I hypersensitivity response is protection primarily against which of the following?

Accepted Answer

Type I hypersensitivity response is also known as an immediate hypersensitivity response, which is primarily involved in the protection against parasites. The response is mediated by immunoglobulin E (IgE) antibodies, mast cells, and eosinophils, which play a pivotal role in parasite expulsion. Conversely, Type II, III, and IV hypersensitivity responses are primarily involved in protection against viruses, bacteria, and fungi, respectively.

Question 16

Which isotype of immunoglobulin is involved in a type I hypersensitivity?

Accepted Answer

Type I hypersensitivity reactions involve the IgE isotype of immunoglobulin, which binds to mast cells and basophils and triggers the release of histamine and other inflammatory mediators. IgA, IgG, and IgM may be involved in other types of hypersensitivity reactions.

Question 17

Type I hypersensitivity involves:

Accepted Answer

Type I hypersensitivity involves IgE binding to mast cells and basophils, leading to the release of histamine and other inflammatory mediators. Phagocytic cell degranulation and proteolytic enzyme activity are not part of type I hypersensitivity. A kidney membrane antigen and specific antibody are involved in type II hypersensitivity. Natural killer cell activation is not typically involved in hypersensitivity reactions.

Question 18

Immune injury resulting from the localization of immune complexes in blood vessels and tissues describes which hypersensitivity reaction?

Accepted Answer

This describes type III hypersensitivity reactions. Type I involves immediate allergic reactions, type II involves cytotoxic reactions, and type IV involves delayed-type cell-mediated reactions.

Question 19

Which of the following occurs in hemolytic disease of the newborn?

Accepted Answer

Hemolytic disease of the newborn occurs when an Rh- mother is exposed to Rh+ fetal cells during pregnancy or delivery, causing an immune response and the production of antibodies against the Rh factor. These antibodies can cross the placenta and attack the Rh+ baby's red blood cells, leading to anemia, jaundice, and other complications. IgE is not typically involved in hemolytic disease of the newborn, and the baby's Rh status is not a factor.

Question 20

A 10-year-old girl has been experiencing symptoms of nasal congestion,watery eyes,and sneezing for the past 2 years.Percutaneous testing revealed that she was allergic to a number of antigens,including ragweed,grasses,dust mites,and cat dander.Treatment with over-the-counter drugs did not do much to alleviate her symptoms,which seemed to worsen with time.Her doctor prescribed allergy immunotherapy,and her symptoms began to improve over the next year.This therapy is thought to work through the administration of:

Accepted Answer

Allergy immunotherapy involves gradually increasing doses of the allergen over time to induce production of blocking IgG4 antibodies. These antibodies can block the binding of allergens to IgE on mast cells and prevent the release of allergy mediators that cause symptoms. This therapy is also sometimes called desensitization or "allergy shots". Options A and B refer to anti-IgE monoclonal antibody therapy, which is a different type of treatment for allergies. Option D is incorrect as IgM antibodies are not typically involved in allergic responses.

Quiz 14: Hypersensitivity