Question 1

Which of the following best describes the mechanism of a Type I (anaphylactic) hypersensitivity reaction?

Accepted Answer

Antigens combine with IgE antibodies on mast cells and basophils, leading to degranulation and release of mediators such as histamine.

Question 2

A patient receives a blood transfusion and develops acute hemolysis. Which hypersensitivity type is most likely responsible, and what is the underlying mechanism?

Accepted Answer

Type II; IgG or IgM antibodies bind to RBC antigens, activating complement and causing cell lysis

Question 3

Which of the following is a key difference between systemic and localized anaphylaxis?

Accepted Answer

Systemic anaphylaxis can lead to circulatory collapse and death, while localized anaphylaxis typically causes symptoms like hives or asthma.

Question 4

A skin prick test is performed to identify allergens. What immunological principle underlies this test?

Accepted Answer

Injection of antigen beneath the epidermis triggers a rapid IgE-mediated inflammatory reaction (wheal) if the person is sensitized.

Question 5

Desensitization therapy for allergies works primarily by:

Accepted Answer

Increasing the production of IgG antibodies that act as blocking antibodies to neutralize the allergen before it binds to IgE.

Question 6

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

Accepted Answer

Type O; because it lacks A and B antigens on the red blood cells.

Question 7

Hemolytic disease of the newborn (HDNB) occurs when:

Accepted Answer

An Rh– mother produces anti-Rh antibodies that cross the placenta and destroy fetal Rh+ red blood cells during a subsequent pregnancy.

Question 8

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

Accepted Answer

Antibodies bind to soluble antigens, forming immune complexes that deposit in tissues and activate complement, leading to inflammation.

Question 9

A patient develops a red, blistering rash after contact with poison ivy. This is an example of which type of hypersensitivity, and what is the mechanism?

Accepted Answer

Type IV; T cell-mediated delayed hypersensitivity

Question 10

Which of the following autoimmune diseases is primarily mediated by T cells attacking insulin-secreting cells?

Accepted Answer

Insulin-dependent diabetes mellitus (Type 1 diabetes)

Question 11

Which of the following best defines the Human Leukocyte Antigen (HLA) complex?

Accepted Answer

A group of genes encoding histocompatibility antigens in humans, important for tissue transplant compatibility.

Question 12

Which type of graft is most likely to be rejected due to the presence of nonhuman antigens?

Accepted Answer

Xenotransplant

Question 13

Which of the following is a limitation of the immune system in controlling cancer?

Accepted Answer

Tumor cells may lack antigenic epitopes for immune recognition.

Question 14

Which of the following is an example of immunotherapy for cancer?

Accepted Answer

Administration of monoclonal antibodies that target tumor antigens.

Question 15

Which of the following best describes a congenital immunodeficiency?

Accepted Answer

An immune deficiency present at birth due to defective or missing genes.

Question 16

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

Accepted Answer

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

Question 17

Which of the following is a reason why HIV is difficult to eliminate from the body?

Accepted Answer

HIV integrates its DNA into host chromosomes, forming a latent provirus.

Question 18

Which of the following drugs is a protease inhibitor used in the treatment of HIV?

Accepted Answer

Atazanavir

Question 19

A patient with AIDS is most likely to have which of the following laboratory findings?

Accepted Answer

CD4+ T cell count below 200 cells/μl

Question 20

Which of the following is the most dangerous route of HIV transmission?

Accepted Answer

Anal-receptive intercourse

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

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