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

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 statements is not true?

a. An antibody has more than one antigen-binding site.

b. A lymphocyte has receptors for multiple different antigens.

c. An antigen can have different epitopes.

d. A liver or muscle cell makes one class 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.

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.

What steps are required for most B cells to become fully activated and differentiate into plasma cells?