Question 1

Which of the following best describes the mechanism behind Type I hypersensitivity reactions?

Accepted Answer

IgE antibodies bind to mast cells and basophils, triggering the release of inflammatory mediators upon allergen exposure.

Question 2

A patient develops a severe, life-threatening allergic reaction after being stung by a bee. Which physiological process is most responsible for the drop in blood pressure observed in this patient?

Accepted Answer

Extensive dilation of blood vessels due to the release of mediators from basophils and mast cells.

Question 3

Which treatment is most effective for preventing systemic anaphylaxis in individuals with known severe allergies?

Accepted Answer

Injection of epinephrine at the onset of symptoms.

Question 4

A child with selective IgA deficiency is most likely to experience which of the following?

Accepted Answer

Frequent respiratory and gastrointestinal infections due to lack of mucosal immunity.

Question 5

Which of the following best explains why a second exposure to an allergen can cause a more severe reaction in a sensitized individual?

Accepted Answer

IgE antibodies already bound to mast cells rapidly trigger degranulation upon allergen binding.

Question 6

A patient receives a blood transfusion with mismatched ABO blood type. Which immune mechanism is primarily responsible for the resulting transfusion reaction?

Accepted Answer

IgM antibodies binding to erythrocyte antigens, activating complement and causing cell lysis.

Question 7

Which of the following is a key difference between Type II and Type III hypersensitivity reactions?

Accepted Answer

Type II targets cell-bound antigens, while Type III involves immune complexes with soluble antigens.

Question 8

A woman who is Rh-negative gives birth to her first Rh-positive child without complications. Why is her second Rh-positive child at risk for hemolytic disease of the newborn?

Accepted Answer

Maternal IgG antibodies, produced after sensitization during the first pregnancy, cross the placenta and attack fetal red blood cells.

Question 9

Which of the following best describes the Arthus reaction?

Accepted Answer

A localized Type III hypersensitivity reaction following injection of antigen into a previously immunized individual.

Question 10

A patient with systemic lupus erythematosus (SLE) is likely to have which of the following immune abnormalities?

Accepted Answer

Antibodies against molecules found in cell nuclei, leading to systemic symptoms.

Question 11

Which of the following is a primary immunodeficiency characterized by the failure of hematopoietic stem cells to produce both T and B lymphocytes?

Accepted Answer

Severe combined immunodeficiency (SCID)

Question 12

A patient develops a rash and joint pain after receiving horse serum for passive immunization. Which hypersensitivity type is most likely responsible?

Accepted Answer

Type III (Immune complex-mediated)

Question 13

Which of the following best explains why immunosuppressive drugs increase the risk of infection in transplant recipients?

Accepted Answer

They inhibit the activation and function of immune cells, reducing the body's ability to fight infections.

Question 14

Which of the following is a common cause of secondary (acquired) immunodeficiency?

Accepted Answer

HIV infection leading to depletion of helper T cells

Question 15

A patient with myasthenia gravis is most likely to have which of the following immune responses?

Accepted Answer

Antibodies bind to acetylcholine receptors, blocking nerve impulses at neuromuscular junctions.

Question 16

Which of the following best describes the mechanism of action of omalizumab in allergy treatment?

Accepted Answer

It binds to the Fc portion of IgE, preventing attachment to mast cells and basophils.

Question 17

Which of the following is a characteristic feature of contact dermatitis?

Accepted Answer

It is a delayed-type hypersensitivity reaction mediated by T cells.

Question 18

Which of the following best explains why RhoGAM is effective in preventing hemolytic disease of the newborn?

Accepted Answer

It contains anti-Rh antibodies that bind fetal Rh-positive erythrocytes, preventing maternal sensitization.

Question 19

A patient with chronic granulomatous disease is most likely to have which of the following defects?

Accepted Answer

Failure to produce hydrogen peroxide and other reactive oxygen species in phagocytes.

Hypersensitivity, Autoimmunity, and Immunodeficiency: Immune System Disorders

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