41. Immune System

What is the primary difference between the innate and adaptive immune responses?

a. The innate immune response does not distinguish between pathogens, while the adaptive immune response does.

b. Only the innate immune response is activated by antigens.

c. The adaptive immune response generates immunological memory and is more specific than the innate immune response.

d. The innate immune response does not kill cells; the adaptive immune response does.

An epitope associates with which part of an antigen receptor or antibody?

a. The tail

b. The heavy-chain constant regions only

c. Variable regions of a heavy chain and light chain combined

d. The light-chain constant regions only

Which statement best describes the difference between responses of effector B cells (plasma cells) and those of cytotoxic T cells?

a. B cells confer active immunity; cytotoxic T cells confer passive immunity.

b. B cells respond the first time a pathogen is present; cytotoxic T cells respond subsequent times.

c. B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells.

d. B cells carry out the cell-mediated response; cytotoxic T cells carry out the humoral response.

Which of the following statements is true?

a. An antibody has one antigen-binding site

b. A lymphocyte has receptors for a single antigen

c. Every antigen has a single epitope

d. A liver or muscle cell makes two classes of MHC molecule

Which of the following best describes the difference in the way B cells and cytotoxic T cells deal with invaders?

a. B cells confer active immunity; T cells confer passive immunity.

b. B cells send out antibodies to attack; certain T cells can do the attacking themselves.

c. T cells handle the primary immune response; B cells handle the secondary response.

d. B cells are responsible for the cell-mediated immune response; T cells are responsible for the humoral immune response.

What is one of the differences between CD4⁺ and CD8⁺ T cells?

a. CD4⁺ cells are immature, and CD8⁺ cells are mature.

b. CD4⁺ cells are activated, and CD8⁺ cells are not.

c. CD4⁺ cells interact with class II MHC proteins, and CD8⁺ cells interact with class I MHC proteins.

d. CD4⁺ cells activate cell-mediated responses, and CD8⁺ cells activate humoral responses.

Which of the following should be the same in identical twins?

a. The set of antibodies produced

b. The set of MHC molecules produced

c. The set of T cell antigen receptors produced

d. The set of immune cells eliminated as self-reactive

Cytotoxic T cells are able to recognize infected body cells because

a. The infected cells display foreign antigens.

b. The infected cells produce antigens.

c. Infected cells release antibodies into the blood.

d. Helper T cells destroy them first.

Explain how gene recombination leads to the production of vast numbers of different B-cell receptors.