81.  Cells that process antigen and present antigens to other immune cells are called  
A.  plasma cells.
B.  antigen-presenting cells.
C.  B receptor cells.
D.  T suppressor cells.
E.  antibodies.

82.  Frequently, several different signals or molecules are needed in order to produce an immune response by a B cell or T cell. The second signal in this process is called  
A.  opsonization.
B.  copresentation.
C.  complement activation.
D.  antigen processing.
E.  costimulation.

83.  Which of the following cytokines is mismatched?  
A.  perforin – makes a hole in target cell membranes
B.  alpha interferon – prevents viral replication
C.  lymphotoxin – costimulator of T cells
D.  interleukin 4 – plays a role in allergic reactions
E.  TNF – activates macrophages and promotes fever

84.  T helper cells possess a glycoprotein called CD4. This molecule binds to  
A.  MHC class I molecules.
B.  MHC class II molecules.
C.  MHC-CD8 antigens.
D.  MHC-CD28 antigens.
E.  Interleukin-1 receptor.

85.  Which of the following might occur after a helper T cell is presented with a processed antigen and costimulated?  
A.  Helper T cells destroy the presenting cell.
B.  Helper T cells produce antibodies.
C.  Helper T cells release interleukins that stimulate B cells to clone.
D.  Helper T cells stop division.
E.  Helper T cells lyse.

86.  Lymphocyte proliferation begins by increasing the number of  
A.  macrophages.
B.  B cells.
C.  T suppressor cells.
D.  helper T cells.
E.  cytotoxic T cells.

87.  Once cytotoxic T cells are produced, which of the following is (are) consistent with their ability to attack intracellular viruses?  
A.  Most nucleated cells process antigens through the MHC class I mechanisms.
B.  Viral antigens are processed by the MHC class I mechanism and are presented to the cell surface.
C.  Cytotoxic T cells bind to MHC class I processed antigens.
D.  Cytotoxic T cells bound to the MHC class I processed antigens release lymphokines.
E.  All of these choices are correct.

88.  Tolerance is a state of  
A.  hypersensitivity.
B.  transplant rejection.
C.  unresponsiveness to antigens.
D.  responding to self-antigens.
E.  non-recognition of antigens.

89.  Tolerance to antigens is induced by  
A.  blocking costimulation.
B.  stimulating interleukin 2 production.
C.  preventing suppressor T cell proliferation.
D.  promoting the release of cytokines.
E.  stimulating helper T cell division.

90. Antibodies are produced by 
A. cytotoxic T cells stimulated by helper T cells.
B. helper T cells stimulated by various cytokines.
C. B cells that differentiate to form plasma cells.
D. natural killer cells as they lyse cancer cells.
E. the red bone marrow.