Question 1

Which of the following best describes the process of B cell activation and clonal selection?

Accepted Answer

A B cell binds its specific antigen, processes it, presents it on a Class II MHC molecule, interacts with a Th cell, and then divides to form plasma and memory B cells.

Question 2

Which antibody class is primarily responsible for the secondary immune response and has the highest affinity for antigens?

Accepted Answer

IgG

Question 3

A patient receives an injection of antibodies after a snake bite. Which type of immunity is this, and what is a key characteristic?

Accepted Answer

Passive immunity; it provides immediate but temporary protection without memory cell formation.

Question 4

Which antibody class is most effective at agglutination and precipitation due to its structure, and why?

Accepted Answer

IgM, because it is a pentamer with 10 antigen-binding sites.

Question 5

What is the main function of the variable region of an antibody molecule?

Accepted Answer

To recognize and bind specific antigens.

Question 6

During a primary immune response, which antibody is produced first and what is the typical lag phase before antibody levels rise?

Accepted Answer

IgM; 4-5 days

Question 7

Which of the following best explains why live, attenuated vaccines are generally avoided in immunocompromised patients?

Accepted Answer

The weakened pathogen could still cause disease in individuals with a compromised immune system.

Question 8

A newborn receives antibodies from its mother through breast milk. Which antibody class is most likely involved, and what type of immunity does this represent?

Accepted Answer

IgA; passive immunity

Question 9

Which antibody class is most associated with allergic reactions and the activation of mast cells?

Accepted Answer

IgE

Question 10

A patient is exposed to a pathogen for the second time. Which of the following best describes the expected immune response?

Accepted Answer

A shorter lag phase (1-3 days) and a rapid, high peak of IgG antibodies.

Question 11

Which of the following is a function of antibodies that helps phagocytes recognize and destroy pathogens?

Accepted Answer

Opsonization

Question 12

Which antibody class is the only one capable of crossing the placenta to provide immunity to the fetus?

Accepted Answer

IgG

Question 13

A patient with a genetic defect cannot produce memory B cells. What is the most likely consequence?

Accepted Answer

They will have a diminished or absent secondary immune response to previously encountered antigens.

Question 14

Which of the following best describes the role of IgD antibodies?

Accepted Answer

They act as antigen receptors on B cells and are involved in B cell activation.

Question 15

Which process allows antibodies to prevent toxins or pathogens from interacting with host cells?

Accepted Answer

Neutralization

Question 16

A patient receives a booster shot for tetanus. What is the immunological basis for the effectiveness of this booster?

Accepted Answer

It stimulates memory B cells to rapidly produce high-affinity antibodies.

Question 17

Which of the following equations best represents the relationship between the number of antigen-binding sites ($$n) $$and the number of antibody subunits ($$s) $$for IgM, given that each subunit has 2 binding sites and IgM is a pentamer?

Accepted Answer

$$n = 2s$$,\ where\ s = 5\ for\ IgM$

Question 18

Which of the following best explains why influenza vaccines must be updated annually?

Accepted Answer

Influenza viruses have a high mutation rate, leading to frequent changes in their antigens.

Question 19

Which antibody class is most likely to be found in mucous membranes and secretions, and what is its structural form?

Accepted Answer

IgA; dimer

Question 20

A patient with an autoimmune disorder produces antibodies that bind to self-antigens. What is the most likely explanation for this phenomenon?

Accepted Answer

Self-reactive B cells escaped deletion during maturation and produce autoantibodies.

Adaptive Immunity: Antibody-Mediated (Humoral) Immunity

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