43. MHC molecules are required for
a. B-cell activation. b. T-cell activation. c. phagocytosis of microbes. d. proteasome degradation of viruses.
44. The figure shown below illustrates a bacterial cell that
Nucleic acids, lipids, polysaccharides, and proteins are released after phagocytosis
a. acts as an antigen. b. is broken down into many antigens.
c. is producing antibodies in response to antigens. d. has a single epitope.
45. An antigen-presenting cell (APC) presents antigen to
a. macrophages to stimulate the synthesis of antibodies.
b. B cells to stimulate the formation of memory B cells.
c. memory T cells to stimulate the synthesis of cytokines.
d. helper T cells to activate the T cells during a cellular response.
46. Which of the following would be expected to elicit the largest production of antibodies?
a. haptens floating freely within plasma b. a complex protein with many different epitopes
c. a polysaccharide with several identical segments d. a small lipid
47. An injection of killed or attenuated Salmonella typhi, the causative agent of typhoid fever, would be expected to protect an individual by
a. causing the individual to have a mild case of typhoid fever, but protecting against future cases of typhoid fever.
b. providing antigens recognizable by the immune system, allowing the formation of memory cells that will prevent typhoid fever in the future.
c. providing cross-protection to prevent several diseases caused by different bacteria.
d. providing the individual with premade antibodies capable of binding to and inactivating Salmonella typhi.
48. When comparing the primary and secondary immune responses, ______ titer levels are ______ during a ______ immune response.
a. IgM; much higher; secondary b. IgG; much higher; secondary
c. IgM; higher than IgG titer levels; primary d. IgM; higher than IgG titer levels; secondary
49. Class switching is the process in which
a. B cells switch from producing IgM of IgD to producing IgE, IgG, or IgA.
b. formed IgM antibody pentamers break apart into IgM monomers.
c. antibody released from the surface of a B cell switches to a different heavy chain.
d. higher-affinity antibodies are produced upon repeated exposure to the same antigen.
50. Why are cytotoxic T (Tc) cells more effective than antibodies at clearing viral infections?
a. Tc cells are able to recognize free viral particles as they circulate through lymph nodes.
b. Antibodies bind weakly to antigen-MHC I complexes on antigen-presenting cells.
c. Antibodies are only able to bind to extracellular antigen, and viruses tend to be intracellular.
d. Tc cells are activated more strongly than B cells by cytokines released by helper T cells.
