Question 1

Which of the following best describes the mechanism underlying Type I hypersensitivity reactions such as hay fever and anaphylaxis?

Accepted Answer

IgE antibodies bind to mast cells and basophils, causing release of inflammatory mediators.

Question 2

A patient receives a blood transfusion and develops fever, hemolysis, and jaundice. Which type of hypersensitivity reaction is most likely responsible?

Accepted Answer

Type II hypersensitivity

Question 3

Which chemical mediator released by mast cells is primarily responsible for the vasodilation and increased vascular permeability seen in allergic reactions?

Accepted Answer

Histamine

Question 4

A child develops a butterfly-shaped rash across the nose and cheeks, kidney failure, and blood abnormalities. Which autoimmune disease is most likely?

Accepted Answer

Systemic lupus erythematosus (SLE)

Question 5

Which blood type is considered the universal donor, and why?

Accepted Answer

Type O, because it lacks A and B antigens on RBCs.

Question 6

A positive tuberculin skin test is an example of which type of hypersensitivity?

Accepted Answer

Type IV (cell-mediated, delayed)

Question 7

Which of the following is a plausible consequence of molecular mimicry in autoimmunity?

Accepted Answer

Antibodies produced against microbial antigens cross-react with host tissues.

Question 8

A patient with DiGeorge syndrome is most likely to have which immunological defect?

Accepted Answer

Defective cell-mediated immunity due to lack of T cells

Question 9

Which of the following best explains why children delivered by cesarean section and with a maternal history of allergy have increased risk of food allergies?

Accepted Answer

They lack early exposure to vaginal and stool bacteria, affecting immune system training.

Question 10

Which equation correctly represents the genotype-phenotype relationship for blood type A?

Accepted Answer

$$A A or$$ $$A O$$ genotype: type A

Question 11

A patient with recurrent bacterial infections is found to have normal T cell function but low levels of immunoglobulins. What is the most likely diagnosis?

Accepted Answer

Agammaglobulinemia

Question 12

Which of the following is a characteristic of Type III hypersensitivity reactions?

Accepted Answer

Antigen-antibody complexes deposit in tissues, causing inflammation.

Question 13

Which autoimmune disease is characterized by antibodies against acetylcholine receptors at the neuromuscular junction?

Accepted Answer

Myasthenia gravis

Question 14

A patient with HIV is most likely to have which type of immunodeficiency?

Accepted Answer

Secondary immunodeficiency

Question 15

Which of the following best describes the process of graft rejection?

Accepted Answer

Recipient T cells recognize donor MHC molecules as foreign and mount an immune response.

Question 16

Which of the following is a plausible outcome of transfusing the wrong blood type?

Accepted Answer

Massive hemolysis, systemic shock, and kidney failure

Question 17

Which type of hypersensitivity is most likely involved in contact dermatitis from poison ivy exposure?

Accepted Answer

Type IV hypersensitivity

Question 18

Which of the following is true regarding the hygiene hypothesis and allergy development?

Accepted Answer

A highly hygienic environment may reduce immune system training, increasing allergy risk.

Question 19

Which of the following equations represents the genotype for a person with type O blood?

Accepted Answer

$$O O$$ genotype: type O

Question 20

Which of the following is a common feature of severe combined immunodeficiencies (SCID)?

Accepted Answer

Absence or dysfunction of both B and T lymphocytes

Disorders in Immunity: Hypersensitivity, Autoimmunity, and Immunodeficiency

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