Download Exam Key 2 2008

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Biology 347
Exam 2 March 27, 2008
NOTE: Turn off all electronics.
Name_______________KEY_________________
Please cover your exam at all time.
I. True/False: (Circle T (true) or F (false) 2 points each, 12 points total)
T F 1. Class II MHC molecules typically bind to longer peptides than do class I molecules.
T F 2. The T cells uses the same set of V, D, and J gene segments as B cells but uses different C gene
segments.
T F 3. T cells expressing CD8 recognize antigen (peptide) presented by MHC class I molecules
T F 4. Clonal anergy occurs in T cells if a costimulatory signal is absent
T F 5. Apoptosis is a critical process in the normal functioning of the immune response system.
T F 6. B cell receptor signaling includes membrane expression of immunoglobulin as well as Ig-alpha
and Ig-beta molecules.
II. Fill in the blanks (2 points each, 12 points total)
1. Fas/Fas ligand belong to the ____tumor necrosis factor______________ family of cytokines
2. EGF/EGFR belong to the _____________growth factor_____________________family of cytokines
3. Class 1 MHC molecules are expressed on _____most nucleated________________cells, expression
of class II MHC molecules are restricted to __dendritic________________________,
___macrophages____________________, and ___B______________ cells.
III. Antigen-antibody reactions. Briefly explain how to conduct each of the immune assays listed below
(4 points each, total of 16 points)
a. Indirect ELISA to detect antibodies to HIV in a serum sample
Trap HIV antigens (usually GAG antigens) in plastic wells of 96 well plate. ( Add milk protein or
albumin to wells to adhere to plate and prevent antibody from adhering to plate--see if the better
students include this, if not, do not count it against them).Wash plate, Incubate plate with serum from
individuals suspected of being exposed to HIV, wash and then add enzyme-linked rabbit or mouse
antibodies to human Ig. Wash, add substrate and observe for color reaction. Color reaction is a positive
test for having antibodies to HIV.
Use your judgment. If they do a competitive ELISA where they lay down a trapping antibody then react
antigen with the serum sample then add to well and examine if antibodies in the serum sample blocked
antigen from binding to trapping antibody--thiswould work--give some credit since it shows that they
know how the ELISA works.
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b. Enhanced ChemoLuminescence (ECL) to detect MHC class I molecules (45 kd) in a cell membrane
preparation
Perform western immunoblot with solubilized membrane preparation. ( Next, transblot proteins to
matrix such as nitrocellulose---see if students get this, if not, don't count it against them). React
transblotted paper with primary antibody to class I proteins. Next, add horse radish peroxidase-linked
secondary antibody + luciferin and oxidizers and expose to x-ray film in the dark. Light emitted will
expose film, indicting where class I molecules are located. Looking for a protein of 45kd in size.
c. ELISPOT to detect T cells secreting IL-4
Plate cells on plastic that has IL-4 trapping antibody. Remove cells (careful attention where cells are
located). Next, add secondary antibody with enzyme. Add insoluble substrate and examine for color
reaction where cells were previously plated.
d. Immunefluorescence to determine the ratio of T helper to cytotoxic T cells in a blood sample
Culture blood cells with fluorescent (green or red) tagged CD4 (red) or CD8 (green). Use fluorescent
activated cell sorter to sort (count) the number of red and green cells. Can also use fluorescent
microscope to manually count cells.
IV. Short Answers/diagram/definitions (total of 50 points. (Be concise and answer in space provided)
1. Define the following terms (3 points each, 15 points total)
a. MHC self restricted
Thymus development of T helper and cytotoxic T cells that are selected on the basis that they
recognize self (at low affinity binding). For both cell types to become activated they must recognize
self and then altered self or self expressing foreign antigen.
b. Antigen processing
Processing of exogenous proteins by antigen presenting cells. For cytotoxic T cells most
nucleated cells process proteins into peptides of approximately 13-18 amino acids and present via class I
proteins. For T helper cells (B cells,dendritic cells,macrophages--count tissue dendritic cells correct if
students list them) digest proteins into peptides of 8-10 amino acids and present to T helper cells via
class II proteins.
c. Haplotype
The set of alleles of linked genes present on one parental chromosome; commonly used in
reference to MHC (class I and II MHC genes).
d. Thymus dependent antibody response
Amplified immune response involving affinity maturation, isotype switching, and generaton of
memory cells. (some students may draw primary and secondary antibody response showing IgM and
IgG levels)
e. Superantigens
Protein from virus, bacteria, parasite that has the ability to bind to APC and T cell with high affinity,
thereby activating T cell in the absence of peptide--i.e, no specificity
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2. Briefly describe the developmental events that occur at each stage of B cell
differentiation/maturation. Indicate which events occur in the bone marrow or in the periphery-germinal centers (3 points each, 15 points total)
a. Pro-B cell (occurs in bone marrow)
Expression of Ig-alpha/Ig-beta receptor on membrane (expressed through out B cell
development)
D-J joining of mu (IgM) heavy chain
b. Pre-B cell (occurs in bone marrow)
V, D, J, C (mu) giving rise to mu heavy chain expressed on membrane. Heavy chain binds to
surrogate "light chain like" protein and under goes cell proliferation, a single cell generating
approximately 250 pre-B cells
c. Immature B cell (occurs in bone marrow)
VJC joining to generate kappa or lambda light chain. Establish B cell tolerance by eliminating
(apoptosis) cells where IgM binds to self antigens. A small percentage of cells escape apoptosis by
editing light chains which involves activation of RAG1 and 2 and replacing VJ regions of light chains
such that the IgM does not interact with self antigens
d. Naive B cell (lymph nodes)
Migrate to lymph nodes--germinal centers, follicles, naive in that they have not been exposed to
antigens of pathogens
e. Mature B cell (lymph node--germinal center--follicles)
exposed to antigens of invading pathogens. Ig undergoes affinity maturation via mutation by
somatic mutations in V region hypervariable regions, undergo class switching and generation of
memory B cells.
3. Diagram and label the various molecules involved in the interaction of a B cell with a T helper cell,
resulting in the activation of the T helper cell and proliferation of the B cell (8 points total)
page 239 of text
4. Explain or diagram positive and negative selection of T cells in the thymus (6 points total)
page 250 of text
V. Multiple Choice (2 point each, 10 points total)
1. A thymus independent antigen will not elicit an immune response involving
A. isotype switching
B. affinity maturation
C. generation of memory B cells
D. A and C are correct
E. A, B, and C are correct
2. Explain the biological consequence of treating fibroblasts and epithelial cells with the cytokine
transforming growth factor beta (TGF-beta)
A. growth inhibition of fibroblasts as well as epithelial cells
B. growth activation of fibroblasts as well as epithelial cells
C. growth activation of fibroblasts and growth inhibition of epithelial cells
D. growth inhibition of fibroblasts and growth activation of epithelial cells
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E. none of the above
3. Treat immature B cells with an antibody that specifically reacts with membrane expressed IgM will
cause the immature B cells to:
A. undergo Ig isotype switching
B. differentiate into mature B cells
C. proliferate
D. undergo apoptosis
E. none of the above
4. Lipopolysachride (LPS) is can be referred to as a
A. polyclonal activator of B cells
B. B cell mitogen
C. T cell independent antigen
D. B and C are correct
E. A, B, and C are correct
5. A mechanism for generating antibody affinity maturation is:
A. light chain editing
B. heavy chain editing
C. substitution of V, D, or J regions
D. somatic mutations in hypervariable regions
E. isotype switching
6. Cytokines can exhibit
A. pleiotrophic effects
B. redundancy
C. synergistic effects
D. antagonistic effects
E. A, B, C, and D are correct
7. Transcription factor that is a key player in immune cell proliferation
A. SP1
B. SP3
C. NFkB
D. FADD
E. BID
8. The interleukin-2 (IL-2) receptor can function as:
A. monimer
B. dimer
C. trimer
D. A and B are correct
E. A, B, and C are correct