Question 1

During a humoral immune response to a newly encountered bacterial infection, B cells are first stimulated to proliferate and then secrete antibodies specific for the bacterium. The antibodies may then bind to the bacteria and facilitate ingestion of the microbes by phagocytic cells. In what phase of the humoral immune response does the binding of secreted antibodies to bacteria occur?

Accepted Answer

A) Recognition phase 
B) Activation phase 
C) Effector phase 
D) Homeostatic phase 
E) Memory phase C

Question 2

The estimated number of distinct structures that can be recognized by the mammalian adaptive immune system is

Accepted Answer

A) 1-10 
B) 10²-10³ 
C) 10³-10⁵ 
D) 10⁷-10⁹ 
E) ∞ D

Question 3

Which of the following best describes clonal expansion in adaptive immune responses?

Accepted Answer

A) Increased number of different lymphocyte clones, each clone specific for a different antigen during the course of an infection 
B) Increased number of different lymphocyte clones, each clone specific for a different antigen during development of the immune system, before exposure to antigen 
C) Increased number of lymphocytes with identical specificities, all derived from a single lymphocyte due to nonspecific stimuli from the innate immune system 
D) Increased number of lymphocytes with identical specificities, all derived from a single lymphocyte stimulated by a single antigen 
E) Increased size of the lymphocytes of a single clone due to antigen-induced activation of the cells D

Question 4

Which of the following infectious diseases was prevented by the first successful vaccination?

Accepted Answer

A) Polio 
B) Tuberculosis 
C) Smallpox 
D) Tetanus 
E) Rubella

Question 5

A vaccine administered in the autumn of one year may protect against the prevalent strain of influenza virus that originated in Hong Kong that same year, but it will not protect against another strain of influenza virus that originated in Russia. This phenomenon illustrates which property of the adaptive immune system?

Accepted Answer

A) Specificity 
B) Amnesia 
C) Specialization 
D) Cultural diversity 
E) Self-tolerance

Question 6

Which of the following cell types is required for all humoral immune responses?

Accepted Answer

A) Natural killer cells 
B) Dendritic cells 
C) Cytolytic T lymphocytes 
D) B lymphocytes 
E) Helper T lymphocytes

Question 7

Which of the following statements is consistent with the process of clonal selection?

Accepted Answer

A) The specificity of a lymphocyte antigen receptor changes to accommodate the structure of an antigen that binds to it. 
B) Many different antigen receptors with different specificities are expressed on each lymphocyte. 
C) Lymphocytes do not express antigen receptors on their cell surfaces until after exposure to antigen. 
D) The diversity of the lymphocyte repertoire for antigens is very small before exposure to antigen but increases significantly after antigen exposure. 
E) The diversity of the lymphocyte repertoire for antigens is very large before exposure to antigen, with millions of different clones of lymphocytes, each having a different specificity.

Question 8

The principal function of the immune system is:

Accepted Answer

A) Defense against cancer 
B) Repair of injured tissues 
C) Defense against microbial infections 
D) Prevention of inflammatory diseases 
E) Protection against environmental toxins

Question 9

A previously healthy 8-year-old boy is infected with an upper respiratory tract virus for the first time. During the first few hours of infection, which one of the following events occurs?

Accepted Answer

A) The adaptive immune system responds rapidly to the virus and keeps the viral infection under control. 
B) The innate immune system responds rapidly to the viral infection and keeps the viral infection under control. 
C) Passive immunity mediated by maternal antibodies limits the spread of infection. 
D) B and T lymphocytes recognize the virus and stimulate the innate immune response. 
E) The virus causes malignant transformation of respiratory mucosal epithelial cells, and the malignant cells are recognized by the adaptive immune system.

Question 10

Antibodies and T lymphocytes are the respective mediators of which two types of immunity?

Accepted Answer

A) Innate and adaptive 
B) Passive and active 
C) Specific and nonspecific 
D) Humoral and cell-mediated 
E) Adult and neonatal

Question 11

Which of the following is a unique property of the adaptive immune system?

Accepted Answer

A) Highly diverse repertoire of specificities for antigens 
B) Self-nonself discrimination 
C) Recognition of microbial structures by both cell-associated and soluble receptors 
D) Protection against viral infections 
E) Responses that have the same kinetics and magnitude on repeated exposure to the same microbe

Question 12

Which of the following statements best describes the "two-signal requirement" for naive lymphocyte activation?

Accepted Answer

A) Lymphocytes must recognize two different antigens to become activated. 
B) Lymphocytes must recognize the same antigen at two sequential times to become activated. 
C) Lymphocytes must recognize antigen and respond to another signal generated by microbial infection to become activated. 
D) Both naive B and naive T lymphocytes must simultaneously recognize antigen for either to be activated. 
E) When lymphocytes recognize antigen, the antigen receptors must activate two-signal transduction pathways to become activated.

Question 13

In addition to T cells, which cell type is required for initiation of all T cell-mediated immune responses?

Accepted Answer

A) Effector cells 
B) Memory cells 
C) Natural killer cells 
D) Antigen-presenting cells 
E) B lymphocytes

Question 14

A standard treatment of animal bite victims, when there is a possibility that the animal was infected with the rabies virus, is administration of human immunoglobulin preparations containing anti-rabies virus antibodies. Which type of immunity would be established by this treatment?

Accepted Answer

A) Active humoral immunity 
B) Passive humoral immunity 
C) Active cell-mediated immunity 
D) Passive cell-mediated immunity 
E) Innate immunity

Question 15

At 15 months of age, a child received a measles-mumps-rubella vaccine (MMR). At age 22, she is living with a family in Mexico that has not been vaccinated and she is exposed to measles. Despite the exposure, she does not become infected. Which of the following properties of the adaptive immune system is best illustrated by this scenario?

Accepted Answer

A) Specificity 
B) Diversity 
C) Specialization 
D) Memory 
E) Nonreactivity to self

Question 16

The two major functional classes of effector T lymphocytes are:

Accepted Answer

A) Helper T lymphocytes and cytotoxic T lymphocytes 
B) Natural killer cells and cytotoxic T lymphocytes 
C) Memory T cells and effector T cells 
D) Helper cells and antigen-presenting cells 
E) Cytotoxic T lymphocytes and target cells

Exam 1: Introduction to the Immune System