Question 1

Which of the following best defines hypersensitivity in the context of immunology?

Accepted Answer

An antigenic response that results in undesirable effects after sensitization to an antigen.

Question 2

A patient experiences a rapid drop in blood pressure and difficulty breathing after a bee sting. Which type of hypersensitivity reaction is this, and what is the primary mediator?

Accepted Answer

Type I (Anaphylactic); Histamine

Question 3

Which of the following best explains why a skin test for allergies produces a rapid wheal-and-flare reaction?

Accepted Answer

IgE antibodies on mast cells bind the allergen, causing degranulation and release of mediators.

Question 4

A child with Crohn’s disease is treated with whipworm eggs. According to the hygiene hypothesis, what is the proposed mechanism for this therapy?

Accepted Answer

Whipworm eggs suppress T helper cell pathways, reducing inflammation.

Question 5

Which of the following is a correct statement about the ABO blood group system?

Accepted Answer

Type AB blood has neither anti-A nor anti-B antibodies in plasma.

Question 6

A woman who is Rh- gives birth to an Rh+ child. Why is the first pregnancy usually unaffected by hemolytic disease of the newborn (HDNB)?

Accepted Answer

The mother has not yet produced significant anti-Rh antibodies during the first pregnancy.

Question 7

Which of the following best describes the mechanism of a Type III (immune complex) hypersensitivity reaction?

Accepted Answer

Antibodies and soluble antigens form complexes that deposit in tissues, activating complement and causing inflammation.

Question 8

A patient develops a rash 48 hours after contact with poison ivy. Which immune mechanism is primarily responsible for this reaction?

Accepted Answer

Type IV hypersensitivity mediated by T cells

Question 9

Which of the following is a cytotoxic autoimmune disease, and what is the primary target?

Accepted Answer

Multiple sclerosis; myelin sheath of nerves

Question 10

Which of the following best explains why a transplanted cornea is usually not rejected?

Accepted Answer

The cornea lacks blood vessels, so antibodies and immune cells do not reach it easily.

Question 11

Which type of transplant is most subject to hyperacute rejection, and why?

Accepted Answer

Xenotransplantation; due to nonhuman antigens

Question 12

Which cytokine is most commonly targeted by immunosuppressant drugs to prevent transplant rejection?

Accepted Answer

Interleukin-2 (IL-2)

Question 13

Which of the following is a real-world example of immunotherapy for cancer?

Accepted Answer

Administration of Herceptin® (a monoclonal antibody) for breast cancer

Question 14

A patient is diagnosed with DiGeorge syndrome. Which immune cells are primarily deficient, and what is the consequence?

Accepted Answer

T cells; absence of cell-mediated immunity

Question 15

Which of the following best describes the attachment of HIV to a host cell?

Accepted Answer

HIV gp120 binds to the CD4 receptor and a coreceptor (CCR5 or CXCR4) on the host cell.

Question 16

Which of the following is a reason why HIV is difficult for the immune system to eliminate?

Accepted Answer

HIV remains as a latent provirus and undergoes rapid antigenic changes.

Question 17

A patient with HIV has a CD4+ T cell count of 150 cells/μL. According to CDC criteria, what is the diagnosis?

Accepted Answer

AIDS

Question 18

Which laboratory test detects HIV RNA in blood before antibodies are present, and what is the principle behind it?

Accepted Answer

Nucleic acid amplification test (NAAT); detects viral RNA using real-time PCR

Question 19

Which of the following is the most common mode of HIV transmission worldwide?

Accepted Answer

Heterosexual contact

Question 20

Why are reverse transcriptase, integrase, and protease considered good targets for HIV chemotherapy?

Accepted Answer

They are enzymes unique to HIV and essential for its replication cycle.

Disorders Associated with the Immune System: Hypersensitivity, Autoimmunity, Transplantation, Cancer, and Immunodeficiencies

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