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IMY521S - IMMUNOLOGY - 2ND OPP - 2ND 2023 |
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nAmlBIA unlVERSITY
OF SCIEnCE Ano TECHnOLOGY
FACULTYOF HEALTH,APPLIEDSCIENCESAND NATURALRESOURCES
DEPARTMENTOF HEALTHSCIENCES
QUALIFICATION:BACHELOROF MEDICALLABORATORYSCIENCES
QUALIFICATIONCODE: 0SBMLS
LEVEL: 5
COURSECODE: IMY521S
COURSENAME: IMMUNOLOGY
SESSION:JANUARY 2023
DURATION: 3 HOURS
PAPER:THEORY
MARKS: 100
SUPPLEMENTARY/ SECONDOPPORTUNITYEXAMINATION PAPER
EXAMINER(S)
DR MAURICENYAMBUYA
MODERATOR:
MS FREDRIKAENGELBRECHT
INSTRUCTIONS
1. Answer ALL the questions.
2. Write clearly and neatly.
3. Number the answers clearly.
PERMISSIBLEMATERIALS
1. Pen
2. Calculator
THIS QUESTION PAPERCONSISTSOF 8 PAGES(including this front page)
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SECTION A [20]
QUESTION 1
[20]
Select the one-lettered answer that fits best in each question. You only need to write
down the letter of the correct answer.
1.1 In the immune response to a hapten-protein conjugate, in order to get
anti-hapten antibodies, it is essential that;
(a) Hapten be recognized by helper T-cells.
(b) The hapten be recognized by natural killer-cells.
(c) The hapten be recognized by suppressor T-cells.
(d) The protein be recognized by B-cells.
(e) The protein be recognized by helper T-cells.
(1)
1.2 Antigen-presenting cells that activate helper T-cells must express which one
of the following on their surface?
(a) CD4
(b) Class I MHC
(c) Class II MHC
(d)
lgM
(e) Thy-1
(1)
1.3 One principal function of complement is to
(a) Bind antibodies attached to cell surfaces and to lyse these cells.
(b) Cross-link allergens.
(c) Inactivate perforin.
(d) Mediate the release of histamine.
(e) Phagocytose antigens.
{1)
1.4 Cytokines always act
(a) Antagonistically with other cytokines.
(b) Act long range.
(c) By binding to specific receptors.
(d) In an autocrine manner.
(e) Synergistically with other cytokines.
(1)
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1.5 Which of the following cytokines is characteristically produced by Th2 lymphocytes
which provide help for antibody production?
(a) GM-CSF
(b) IL-1
(c) IL-4
(d) IFN-y
(e) TNF-a
(1)
1.6 High-affinity B cell clones are usually generated by
(a) Class switching.
(b) Expression of high affinity precursors in the naive B cell population.
(c) Positive selection.
(d) Negative selection.
(e) Somatic hypermutation.
(1)
1.7 Prior to class-switching, B cells express
(a) lgA
(b) lgA and lgG
(c) lgD
(d) lgD and lgM
(e) No surface antibody
(1)
1.8 Which of the following is a primary lymphoid organ?
(a) Lymph nodes
(b) Peyer's Patches
(c) Spleen
(d) Thymus
(e) Tonsil
(1)
1.9 When antigen reaches the lymph node
(a) There is an increase in the number of cells leaving the lymph node.
(b) There is a decrease in the number of cells leaving the lymph node.
(c) There is an immediate increase in the number of activated B cells.
(d) It is transported to the spleen.
(e) It is immediately destroyed by the macrophages.
(1)
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1.10 The specialised cell type involved in the entry of lymphocytes into a lymph
node is called
(a) HEV endothelial cells
(b) M cells
(c) PALScells
(d) Selectins
(e) Synovial cells
(1)
1.11 The following is characteristic of B cells but not T cells:
(a) CD3
(b) CD40 ligand
(c) MHC class I
(d) Polyclonal activation by concanavalin A
(e) Surface immunoglobulin
(1)
1.12 A Fab fragment
(a) Is produced by pepsin treatment.
(b) Is produced by the separation of heavy and light chains.
(c) Binds antigens.
(d) Lacks light chains.
(e) Has no interchain disulphide bonds.
(1)
1.13 Pattern recognition receptors include
(a) PAMPs
(b) LPS
(c) Lipotechoic acid
(d) Lectin-like molecules
(e) Bacterial peptidoglycan
(1)
1.14 The complement component C3 is cleaved by
(a) Factor D
(b) C4b2a3b
(c) C3bBb
(d) C3b
(e) Cls
(1)
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1.15 C3b
(a) Opsonises bacteria.
(b) Is an anaphylatoxin.
(c) Is chemotactic.
(d) Is the inactive form of C3.
(e) Directly injures bacteria.
(1)
1.16 Positive selection in the thymus is mediated by:
(a) B cells.
(b) Cortical epithelial cells.
(c) Follicular dendritic cells.
(d) lnterdigitating medullary cells.
(e) Macrophages.
(1)
1.17 Specific antibodies are readily detectable in serum following primary contact
with antigen after
(a) 10 minutes.
(b) 1 hour.
(c) 5-7days.
(d) 3-5 weeks.
(e) Only following a second encounter with the antigen.
(1)
1.18 The antigen portion on an antigen -presenting cell that is recognised by the
a~-TCR is
(a) The native protein antigen together with the Major Histocompatibility
Complex molecule.
(b) Processed peptide antigen together with the Major Histocompatibility
Complex molecule.
(c) Processed peptide antigen.
(d) Native antigen.
(e) The Major Histocompatibility Complex molecule alone.
(1)
1.19 Antigen processing for presentation by an MHC class II molecule involves
(a) Calnexin
(b) HLA-DM
(c) LMP2
(d) Proteasome
(e) TAP 1 and TAP 2
(1)
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1.20 Suppression of Th2 lymphocytes by Th1 lymphocytes may be mediated by
(a) IL-4
(b) GM-CSF
(c) IL-1
(d) TNF-13
(e) INF-y
(1)
SECTION B [80]
QUESTION 2
[55]
Thando had been a healthy until she developed pneumonia caused by Pneumocystis
jirovecii, an opportunistic pathogen, at the age of 7 months. The paediatrician suspected
that she may have a severe combined immunodeficiency disease and ordered an
investigation of her lymphocyte functions. The T cells were found to have normal
proliferative activity but further diagnostic tests revealed that her T cells could not
respond to specific antigen stimuli. Her serum antibody levels were determined (see
results in the table below). Analysis of her B cells revealed that there were no HLA-DQ or
HLA-DRmolecules. All tests pointed to the fact that she did not have Severe Combined
Immunodeficiency Disease but that she had inherited an autosomal recessive trait of her
HLA-DQ& HLA-DRwhich explains the absence of HLA-DQ and HLA-DRmolecules. She
received a bone marrow transplant from her brother and her immune function was
restored. Her co4+ cells were also very low in number. Normally, her co4+ count would be
expected to be twice her cos+ T-lymphocyte count.
TEST
RESULT
COMMENT
Leukocytes
Lymphocytes
Neutrophils
Monocytes
Eosinophils
B lymphocytes
T lymphocytes
Helper T cells *
Cytotoxic T cells *
lgM
lgG
lgA
20 000 cells /µf,
10%
82%
6%
2%
27%
47%
10%
34%
30 mg/de
96 mg/dt
6 mg/de
4000-7000 cells/µ£
normal:
normal:
normal:
40-345 mg/de
600-1400 mg/dt
60-380 mg/df,
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2.1 Comment on the levels of leucocytes in her body. Include what the expected levels
would be.
(6)
2.2 What function is affected by the absence of HLA-DQ and HLA-DRmolecules?
(1)
2.3 Why is it important that B lymphocytes have HLA-DQ and HLA-DRmolecules?
(1)
2.4 In the event that Thando has a S.aureus infection and a healthy immune system,
describe the events leading to the activation and differentiation of B cells. S. aureus
are extracellular pathogens. Mention the cytokines that are involved.
(8)
2.5 Sketch and label a HLA-DQ molecule named (½ mark per label).
(6)
2.6 Describe how S.aureus would be processed and presented if HLA-DQ and HLA-DR
molecules were present and functional.
(12)
2.7 The activation of Band T lymphocytes would take place in the lymph node. Describe
the organisation of the lymphoid cells in this structure.
(9)
2.8 T lymphocytes tend to spend more time outside the lymph node and spleen than B
cells. Explain how a na'ive T lymphocyte which found itself in blood could gain entry
into the lymph node to see whether it could recognise any antigen that had been
sequestered in the lymph node and then leave the lymph node if it didn't become
activated.
(12)
QUESTION 3
[25]
Shawn is diagnosed with nasopharyngeal diphtheria, a disease in which the bacterial
specie, Corynebacterium diphtheriae produces a neurotoxin. The toxin is then able to
enter the epithelial cells of the upper respiratory tract and cause necrosis (the death)
of epithelial cells as well as polymorphonuclear cells in the underlying tissue.
3.1 Our bodies are constantly under threat by infectious organisms trying to get
access to our bodies. Fortunately, commensals are able to protect us and
prevent the entry of the bacteria. Explain how commensals can prevent entry
of pathogens into our body.
(1)
3.2 Once the Corynebacteria gain access to Jonathan's tissues, the Corynebacteria
are confronted with phagocytes in the underlying tissue and inflammation sets
in. How are the phagocytes able to recognize and attack the Corynebacteria?
(2)
3.3 Which phagocyte would the Corynebacteria first encounter at the site of
infection? Give a reason for your answer.
(2)
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3.4 Discuss the features of the adaptive immune response that makes it more
effective in protecting Jonathan's body in the long run against Corynebacteria. (15)
3.5 Fortunately, the cases of diphtheria are few thanks to vaccination. Name the
person who performed the first vaccination as we know it today and describe
the events leading up to and including this significant event.
(5)
End of Examination
Total Marks: [100]
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