Question 1

Which of the following best describes the main difference between the third line of defense (adaptive immunity) and the first two lines of defense in the immune system?

Accepted Answer

The third line of defense is only activated after exposure to a specific antigen and generates immunological memory.

Question 2

Which of the following statements correctly distinguishes between an antigen, an immunogen, and an epitope?

Accepted Answer

An antigen is any molecule that can be seen and identified by the immune system; if it provokes a response, it is called an immunogen; an epitope is the specific part of the antigen recognized by immune cells.

Question 3

Which of the following is NOT a characteristic of a 'good' immunogen?

Accepted Answer

Highly repetitive structure with no variability

Question 4

A patient receives a blood transfusion and experiences a severe immune reaction due to differences in cell surface markers. Which type of antigen is most likely responsible for this reaction?

Accepted Answer

Alloantigen

Question 5

Which of the following best explains why B cells can respond to a nearly infinite variety of antigens?

Accepted Answer

B cells rearrange gene segments that code for antigen receptors, generating immense diversity before antigen exposure.

Question 6

Which of the following cell types is NOT considered a professional antigen-presenting cell (APC)?

Accepted Answer

T helper cell

Question 7

A small molecule such as penicillin can trigger an allergic reaction only after binding to a larger carrier protein in the body. What is the immunological term for penicillin in this context?

Accepted Answer

Hapten

Question 8

Which of the following best describes the role of MHC class II molecules in the immune response?

Accepted Answer

They are found on macrophages, dendritic cells, and B cells, and present processed antigens to helper T cells.

Question 9

Which of the following is a correct sequence of events in the adaptive immune response?

Accepted Answer

Lymphocyte development and clonal deletion → Antigen presentation and clonal selection → Challenge of B and T cells by antigens → T and B cell responses

Question 10

Which of the following best describes the function of cytotoxic T cells (CD8+)?

Accepted Answer

They destroy infected host cells, cancer cells, and foreign graft cells by recognizing antigens presented with MHC class I molecules.

Question 11

Which of the following statements about antibody structure is correct?

Accepted Answer

Each antibody molecule has two identical antigen-binding sites formed by variable (V) regions.

Question 12

A patient receives an injection of gamma globulin after exposure to hepatitis A. Which type of immunity is this an example of?

Accepted Answer

Artificial passive immunity

Question 13

Which of the following best explains why booster shots are sometimes necessary for vaccines?

Accepted Answer

Booster shots help maintain long-term immunity by re-exposing the immune system to the antigen, increasing memory cell numbers and antibody titers.

Question 14

Which of the following is a property of T-cell-independent antigens?

Accepted Answer

They can directly activate B cells without T cell help, often being polysaccharides with repeating units.

Question 15

Which immunoglobulin class is most prevalent in serum and is responsible for long-term immunity and memory?

Accepted Answer

IgG

Question 16

Which of the following best describes the principle of herd immunity?

Accepted Answer

Herd immunity is achieved when a certain percentage of the population is vaccinated, reducing the likelihood of disease spread and protecting unvaccinated individuals.

Question 17

Which of the following vaccine types uses a live, weakened form of the pathogen to stimulate immunity?

Accepted Answer

Live, attenuated vaccine

Question 18

Which of the following is a function of the Fc region of an antibody?

Accepted Answer

Binding to receptors on phagocytes, mast cells, and basophils to mediate immune responses such as opsonization and allergic reactions

Question 19

A child receives antibodies against diphtheria toxin from an injection, but does not develop memory cells. Which equation best represents the antibody titer ($$T) $$over time ($$t) in $$this scenario, assuming a rapid decline after administration?

Accepted Answer

$$T(t) = T_0$ e$$^{-kt}$$, where T_0$ is the initial titer and k$ is a positive constant$

Question 20

Which of the following best describes the process of clonal deletion?

Accepted Answer

The destruction of self-reactive lymphocyte clones during development to prevent autoimmunity

Adaptive Immunity and Immunization: Host Defenses II (Chapter 13 Study Notes)

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