Question 1

Which of the following best describes the difference between humoral and cellular immunity in the adaptive immune response?

Accepted Answer

Humoral immunity eliminates extracellular pathogens via antibodies, while cellular immunity eliminates intracellular pathogens via T cells.

Question 2

Which antibody class is the first to be produced during a primary immune response and is also the only antibody class that can be formed by the fetus?

Accepted Answer

IgM

Question 3

A patient receives a vaccine and, upon re-exposure to the same pathogen years later, mounts a rapid and effective immune response. Which cell type is primarily responsible for this secondary response?

Accepted Answer

Memory B cells

Question 4

Which region of the antibody molecule is responsible for binding to antigens?

Accepted Answer

Fab region

Question 5

Which of the following is a protective outcome of antibody-antigen binding that enhances phagocytosis by coating bacteria?

Accepted Answer

Opsonization

Question 6

Which class of antibody is most abundant in serum and is the only one that can cross the placenta to provide passive immunity to the fetus?

Accepted Answer

IgG

Question 7

A B cell is activated and begins to produce IgG instead of IgM. This process is known as:

Accepted Answer

Class switching

Question 8

Which of the following best describes the role of cytotoxic T cells (Tc, CD8+) in the immune response?

Accepted Answer

They induce apoptosis in infected or cancerous 'self' cells presenting antigen with MHC class I.

Question 9

Which of the following is true regarding antigen-presenting cells (APCs)?

Accepted Answer

They present antigen fragments with MHC class II to helper T cells.

Question 10

Which of the following is a characteristic of T-independent antigens?

Accepted Answer

They can activate B cells without helper T cells, often being polysaccharides or lipopolysaccharides.

Question 11

Which of the following best explains why IgA is important in mucosal immunity?

Accepted Answer

It is found as a dimer in secretions such as breast milk, mucus, tears, and saliva.

Question 12

Which process describes the selection and multiplication of lymphocytes that bind a specific antigen, resulting in a population of identical cells?

Accepted Answer

Clonal selection and expansion

Question 13

Which of the following is true about the role of helper T cells (TH, CD4+) in the immune response?

Accepted Answer

They orchestrate the immune response by activating B cells and macrophages via cytokine secretion.

Question 14

Which of the following best describes the function of natural killer (NK) cells?

Accepted Answer

They recognize and kill host cells lacking MHC class I molecules, often during viral infection.

Question 15

A patient with a genetic defect in MHC class II molecules would most likely have impaired:

Accepted Answer

Activation of helper T cells

Question 16

Which of the following best describes affinity maturation?

Accepted Answer

The process by which B cell receptors become more specific to an antigen through natural selection.

Question 17

Which of the following is a correct statement about the lymphoid system?

Accepted Answer

Secondary lymphoid organs are sites where lymphocytes gather to encounter antigens, such as lymph nodes and spleen.

Question 18

Which of the following best explains why vaccines are effective in preventing infectious diseases?

Accepted Answer

They exploit immunologic memory by generating memory cells that respond rapidly upon re-exposure to the pathogen.

Question 19

Which of the following is a unique feature of IgE antibodies?

Accepted Answer

They are active in allergic reactions and barely detectable in circulation.

Question 20

Which of the following best describes the process of complement activation by antibodies?

Accepted Answer

Antibody binding to antigen triggers the classical pathway, leading to inflammation, lysis of foreign cells, and opsonization.

Adaptive Immunity: Mechanisms and Responses

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