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Biol 430
Question Bank
MHC and Antigen Presentation
1. Describe the structures of MHC-I and MHC-II proteins.
A. Draw a schematic diagram of an MHC-I type
protein and label its peptide subunits.
-------------------------------- membrane
B. The diagram to the right shows a cross-section
of the MHC-I binding cleft. Add to the
diagram a 15 amino acid peptide of around
showing how it would be positioned. Label
the position of the anchor amino acids.
C. Draw a simplified diagram of an MHC-II
type protein and label its peptide subunits.
-------------------------------- membrane
D. The diagram to the right shows a cross-section
of the MHC-I binding cleft. Add to the
diagram a 15 amino acid peptide of around
showing how it would be positioned. Label
the position of the anchor amino acids.
2. Complete this table to show the arrangement of MHC-I, MHC-II and MHC-III regions and genes
on the chromosome.
MHC class:
Locus:
N/A
A. Although there are the same number of MHC-I and MHC-II loci, a greater number of MHC-II
peptides can be created. Why?
B. MHC-II loci include pseudogenes; what are these and do they contribute to the range of
peptides presented by MHC proteins?
Biol 430
Question Bank
MHC & AG-Presentation
Page 1
3. Identify the meaning of each of the following designations:
A. DRα and DRβ :
B. DRA and DRB :
C. DRB1, DRB2, DRB3, etc :
D. DRB1*01, DRB1*02, DRB1*03, etc :
E. DRB1*0101, DRB1*0102, DRB1*0103, etc :
F. DR1, DR2, DR3, etc
4. Match each of the following terms with its best explanation.
Term
1. ___ Codominance
a. MHC proteins contain more than one peptide subunit.
2. ___ Polygenicity
b. A MHC protein can bind to a many different peptides.
3. ___ Promiscuous binding c. There are several genes for MHC-I and MHC-II proteins
4. ___ Quartenary structure d. Within the population there are many alleles for the MHC genes.
5. ___ Polymorphism
e. HLA genes on both homologous chromosomes are expressed.
5. Answer the following questions about haplotypes referring to this table.
A
B
C
DR
A1 B7 Cw3 DR2
A2 B8 Cw2 DR3
A3 B44 Cw4 DR4
A11 B35 Cw1 DR7
A3 B44 Cw4 DR7
DQ
DQ1
DQ2
DQ2
DQ3
DQ3
DP
DP1
DP2
DP3
DP4
DP5
F
G
H
E
R
A. A, B, C, DR, DQ, and DP represent different ___________________.
B. A1, B8, Cw3, DR2, etc., represent different ___________________
C. F, G, H, E, and R designate different _____________________.
D. If a HLAG/H man marries a HLAH/E woman, what are the potential haplotypes among their
children. (Hint: predicting haplotypes among offpring can be treated like a monohybrid
cross.)
E. In theory, would a person who is HLAF/F or a person who is HLAF/G be better able to raise an
immune response against the greatest number of pathogens? Explain.
Biol 430
Question Bank
MHC & AG-Presentation
Page 2
6. Consider a hypothetical allelic combination HLA-B4 and HLA-C6 that presents a relative risk of
150 for a particular autoimmune disease.
A. Will all people that have the disease carry these two alleles?
B. Will everyone with these two alleles get the disease?
C. What other factors might influence incidence of the disease?
7. You cross a homogenous C57Bl/6 (H-2b) mouse and homogenous CBA (H-2k) mouse, and
examine the H-2 protein expression among the offspring. This diagram shows the arrangement of
MHC genes in the mouse MHC complex.
MHC class:
Locus:
I
K
II
A
III
E
I
D
L
A. What H-2 haplotype(s) will be carried by the F1 offspring? Will the offspring be syngeneic?
B. Which types of MHC will be expressed on the liver cells of the offspring? Which will be
expressed on dendritic cells?
8. In an investigation of induction of B-cell tolerance to self-antigens, Nemazee and Burki created
two transgenic mice strains. One received the gene for an antibody against the Kb protein, the other
received this gene as well as the Kb gene. In the single transgenic mice, B-cells expressing the antiKb antibody were found in the bone marrow and lymph nodes, but these B-cells were found only in
the bone marrow of double transgenic mice.
A. What does the expression ‘Kb’ mean?
B. Was the haplotype of the mice receiving the genes H-2b or a different haplotype? Explain.
C. If the mice did have a haplotype of H-2b, how would the results have been different?
Biol 430
Question Bank
MHC & AG-Presentation
Page 3
8. As a student in an immunology laboratory class, you have been given spleen cells from a mouse
immunized with the LCM virus. You determine the antigen-specific functional activity of these cells
with two different assays: in assay 1, the spleen cells are incubated with macrophages that have
been briefly exposed to the LCM virus; the production of interleukin 2 (IL-2) is a positive response;
in assay 2, the spleen cells are incubated with LCM -infected target cells; lysis of the target cells
represents a positive response in this assay. The results of the assays using macrophages and target
cells of different haplotypes are presented in the table below.
MHC Haplotype of macrophages
and virus-infected target cells
Mouse strain used as
source of macrophages
& target cells
C3H
MHC-I
K
k
MHC-II
A
E
k
k
BALB/c
BALB/c x B10.A
A.Tl
B10.A (3R)
B10.B (3R)
d
d/k
s
b
k
d
d/k
k
b
k
MHC-I
D
k
d
d/k
k
b
--
Response of spleen cells
IL-2 production by
Lysis of LCMT-cells (assay 1) infected cells (assay
2)
+
-
d
d/d
d
d
b
+
+
+
+
+
+
+
-
A. The activity of which T-cell population is detected by each assay?
B. The functional activity of which MHC molecule is detected in each assay?
C. MHC molecules of which haplotypes are required for the response to LCM in each of the two
assays?
9. For each of the following cell types, indicate if it will express MHC I, II, both (B), or neither (N).
___ B-cells
___ Dendritic cell
___ Liver cell
___ Red blood cell
___ T-cell
___ Macrophage
___ Skin cell
10. In order to function as effective APCs, DCs muct undergo a series of activation steps. What
change to a DC occurs during each one of these steps:
A. What are several ways in which DCs receive a danger signal and capture an antigen? What
are some of the changes that occur to a DC cell upon sensing a danger signal?
B. What changes occur to a DC cell after engaging a T-cell?
Biol 430
Question Bank
MHC & AG-Presentation
Page 4
11. Figure (a) shows the mouse parental MHC haplotypes
and that of their offspring. The lower diagram shows an
experimental design where skin is grafted from the donor
mice (center column) to either inbred mice (left-hand
column) or to heterzygous mice (right-hand column).
Same-colored mice are syngeneic.
A. What do the designations b/b or k/k or b/k signify
about each mouse?
B. In which of the recipients will the skin graft be
perceived as ‘self’?
C. Which of the mice will reject the skin grafts?
Explain why.
12. Referring to the Figure A:
A. Identify the structures labeled A - D and the
cellular compartments labeled as D and F.
A
B. What type of MHC is being loaded with
peptide?
C. In which cell types does this process occur?
D. Explain the process that is occurring in the
compartment labeled as C
Biol 430
Question Bank
MHC & AG-Presentation
Page 5
13. Referring to the figure to Figure B:
A. Identify the structures labeled A - D and the
cellular compartments labeled as D and F.
B
B. What type of MHC is being loaded with
peptide?
C. In which cell types does this process occur?
D. Explain the process that is occurring in the
compartment labeled as F
16. Morrison and Braciale performed experiments that demonstrated the presence of two antigen
processing pathways. They used two Tc cell clones that
Activation of Tc cells
DC
that recognize antigens on:
recognized influenza hemagglutin (HA, one of the
treatment
MHC-I
MHC-II
immunogenic surface proteins of the flu virus)
presented either on MHC-I or MHC-II. DCs were
Infectious virus
+
+
incubated with either infectious or inactivated forms of
the virus. The inactivated form retained its antigenic
Inactivated virus
+
properties but was unable to infect host cells.
Furthermore, the treatments included chloroquine (the
Infectious virus
+
most common treatment for malaria) which blocks
+ emetine
Infectious virus
endocytosis, or emetine, which inhibits viral
+
+ chloroquine
replication. After each treatment, the DCs were tested
for their ability to activate the Tc cells and the results are shown in the table.
A. Why are both cell types activated by DCs treated with infectious virus.
B. Which antigen processing pathway would you expect to not function in cells:
a. exposed to inactivated virus? _________________________
b. treated with emetine? ________________________
c. treated with chloroquine? _______________________
C. Do the results concur with these predictions? Explain.
D. Explain how these results demonstrate the operation of two separate pathways of antigen
processing.
E. Does cross-presentation appear to be occurring in these DC cells? Explain.
Biol 430
Question Bank
MHC & AG-Presentation
Page 6
14. Ziegler and Unanue performed some of the key experiments that demonstrated antigen
processing in DC cells. As part of the experiments, the DCs were treated with paraformaldehyde to
cause ‘fixation’, such as in a
histology procedure, which blocks
all enzymatic activity and ‘locks’ the
cells’ proteins in place. The ability
of the DC’s to activate TH cells that
recognize egg-white albumin
(ovalbumin, ‘OVA’) was tested by
measuring release of IL-2 after
several alternative treatments:
(a) DCs were fixed and then
exposed to the OVA.
(b) DCs were incubated with
OVA for an hour and then fixed.
(c) DCs were fixed and then
incubated with OVA peptide
fragments.
In the diagram, OVA peptides in
MHC are colored red, other peptides
are colored blue. The results are
shown in the right-hand column. (Figure is adapted from Goldsby, et al. 2003. Immunology. 5 th ed. Figure 8.3)
A. Why are peptides present in the MHC proteins even before exposure to OVA?
B. Does fixation appear to alter the ability of MHC proteins to interact with T-cell receptors?
Explain.
C. Why do the DCs fail to activate the TH cells in experiment (a)?
D. What does experiment C show about the ability of mature MHC proteins to exchange
peptides? Do you think this process is likely to occur in vivo?
E. Explain how this experiment demonstrates the need for antigen processing.
Biol 430
Question Bank
MHC & AG-Presentation
Page 7
Biol 430
Question Bank
MHC & AG-Presentation
Page 8