Question 1

A patient develops hives and difficulty breathing within minutes after eating peanuts. Which type of hypersensitivity reaction is most likely responsible, and what is the primary immune mediator involved?

Accepted Answer

Type I hypersensitivity; mediated by IgE and mast cells

Question 2

Which of the following best describes the mechanism of tissue damage in Type II (Cytotoxic) hypersensitivity reactions?

Accepted Answer

Antibodies bind to cell surface antigens, leading to cell lysis via complement or phagocytosis

Question 3

A patient receives a mismatched blood transfusion and develops hemolysis within hours. Which hypersensitivity type is this, and what is the main effector cell?

Accepted Answer

Type II; Antibodies and complement

Question 4

Which of the following is a classic example of a Type III hypersensitivity reaction?

Accepted Answer

Serum sickness following administration of antitoxin

Question 5

A patient develops a red, itchy rash 48 hours after exposure to nickel jewelry. Which hypersensitivity type is involved, and what is the main immune cell responsible?

Accepted Answer

Type IV; CTLs

Question 6

Which of the following best explains why corticosteroids are effective in treating Type IV hypersensitivity reactions?

Accepted Answer

They suppress T cell-mediated immune responses

Question 7

Which of the following equations best represents the formation of immune complexes in Type III hypersensitivity?

Accepted Answer

$\mathrm{Antigen} + \mathrm{Antibody} \rightarrow \mathrm{Immune\ Complex}$

Question 8

Which hypersensitivity reaction is most likely to be involved in the development of autoimmune hemolytic anemia, and what is the underlying mechanism?

Accepted Answer

Type II; Antibodies bind to red blood cell antigens, leading to cell destruction

Question 9

A patient with systemic lupus erythematosus (SLE) experiences joint pain and a rash due to immune complex deposition. Which hypersensitivity type is this, and what is the main inflammatory cell involved?

Accepted Answer

Type III; Neutrophils

Question 10

Which of the following best describes the time course and mechanism of a Type IV hypersensitivity reaction?

Accepted Answer

Hours to days; T cell-mediated cytotoxicity

Question 11

A newborn develops hemolytic disease due to Rh incompatibility. Which hypersensitivity type is this, and what is the best preventive treatment?

Accepted Answer

Type II; Administration of anti-Rh immunoglobulin (RhoGAM)

Question 12

Which of the following is NOT a typical effector mechanism in Type II hypersensitivity reactions?

Accepted Answer

Release of histamine from mast cells

Question 13

Which of the following best explains why antihistamines are effective in treating Type I hypersensitivity reactions?

Accepted Answer

They inhibit the action of histamine released from mast cells

Question 14

A patient develops serum sickness after receiving horse antitoxin. Which immune components are primarily responsible for the symptoms?

Accepted Answer

Antigen-antibody complexes and complement

Question 15

Which of the following best describes the role of neutrophils in Type III hypersensitivity reactions?

Accepted Answer

They phagocytose immune complexes and release enzymes causing tissue damage

Question 16

Which of the following is a key difference between Type I and Type IV hypersensitivity reactions?

Accepted Answer

Type I is antibody-mediated, while Type IV is cell-mediated

Question 17

Which of the following best explains the use of immunosuppressive drugs in the treatment of Type II and Type IV hypersensitivity reactions?

Accepted Answer

They inhibit the activation of T cells and/or antibody production

Question 18

Which of the following scenarios best illustrates a Type IV hypersensitivity reaction?

Accepted Answer

A healthcare worker develops a positive tuberculin skin test 48 hours after injection

Question 19

Which of the following best describes the sequence of events in a Type I hypersensitivity reaction?

Accepted Answer

Antigen exposure $\rightarrow$ IgE production $\rightarrow$ IgE binds mast cells $\rightarrow$ Re-exposure $\rightarrow$ Mast cell degranulation

Question 20

Which of the following is the most appropriate initial treatment for a severe Type I hypersensitivity reaction (anaphylaxis)?

Accepted Answer

Epinephrine injection

Summary of Hypersensitivity Reactions

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