1. The initial complement component activated by complement-fixing antibodies is:
A C1q
B C1s
C C3b
D C5a
E C9
A
The constant region of IgM and of most IgG antibodies binds C1q after the antibody has complexed with antigen. This eventually leads to the generation of a C4b2a convertase which splits C3. C1s binds only after C1q and C1r have bound. C3b can be generated by the classical, lectin, or alternative pathway. C3 convertases and acts as an opsonin. C5a is generated by C5 convertase and acts as a powerful chemotaxin for neutrophils and an anaphylatoxin causing degranulation of mast cells. C9 is the final component in the complement cascade and, under the influence of C5–8, polymerizes to form part of the membrane attack complex (MAC).
2. Several of the complement components are:
A Glycolipids
B Cell surface molecules of lymphocytes
C Precursors of enzymes
D Hormones
E Antibodies
C
Upon splitting, individual components form enzymatically active complexes that act in a sequential proteolytic cascade. The complement components are all proteins or glycoproteins. Although they may become deposited on the cell surface following activation, they are normally present in soluble form in blood and tissue fluids. Note, however, that several receptors for complement components are present as cell surface molecules on lymphocytes and other cell types. The complement components are produced by several different cell types and do not function as hormones. Antibodies are the specific recognition molecules that bind antigen.
3. The classical and alternative pathways meet at complement component:
A C4
B C4b
C Factor D
D C5
E C3
E
Each pathway of complement activation produces a C3 convertase, either C4b2b (classical and lectin pathways) or C3bBb (alternative pathway), which cleaves C3 into C3a and C3b. C4 is only found in the classical and lectin pathways. Note that the complement components are numbered in the order they were first identified rather than the order in which they act. C4b is produced by cleavage of C4 by C1qrs or MBL/MASP1/2 and forms part of the classical and the lectin pathways of complement activation. Factor D is found in the alternative pathway and cleaves factor B in the C3bB complex to produce C3bBb, the alternative pathway C3 convertase. C5 is one of the later complement components which upon being split by C5 convertase forms the anaphylatoxin C5a and may go on to form the membrane attack complex containing complement components C5b, C6, C7, C8, and C9.
4. Clonal selection occurs when antigen is encountered by:
A Neutrophils
B Mast cells
C T-cells
D Basophils
E Eosinophils
5. Which of the following statements is TRUE of plasma cells?
A Plasma cells have a thin layer of cytoplasm
B Plasma cells are derived from T-cells
C Plasma cells develop into B-cells
D Plasma cells secrete large amounts of IFNγ
E Plasma cells have a high RNA content
6. Specific antibodies are readily detectable in serum following primary contact with antigen after:
A 10 min
B 1 h
C 5–7 days
D 3–5 weeks
E Only following a second contact with antigen
7. A single plasma cell secretes:
A Antibody of a single specificity related to that on the surface of the parent B-cell
B Antibody of two antigen specificities
C The antigen it recognizes
D Many different types of antibody
E Lysozyme
8. Immunological memory can be transferred experimentally by:
A Antibody
B Complement
C Phagocytes
D Lymphocytes
E Serum
D
9. What is the main reason an experimental animal treated with X-rays can act as a living test tube for lymphocyte transfer experiments?
A It is microbiologically sterile
B Complement components will be inactivated
C The host lymphocytes are destroyed or unable to divide
D Only non-dividing cells are affected
E The requirement for T-cell help is overcome
10. What is immunological unresponsiveness to self-antigens called?
A Tolerance
B Tolerogen
C Memory
D Acquired immunity
E Antibody-dependent cellular cytotoxicity (ADCC)
11. Edward Jenner vaccinated against smallpox using:
A Killed smallpox virus
B A recombinant protein derived from smallpox
C An unrelated virus
D Toxoid
E Cowpox
12. Protective antibodies against infectious agents are often:
A Autoantibodies
B Neutralizing
C Toxoids
D Natural killer (NK)
E Non-specific
B
13. Intracellular parasites within macrophages are killed more readily in the presence of:
B Kinins
C Properdin
D IFNγ
E Anaphylatoxin
14. T-cell surface receptors for antigen partly recognize:
A Cytokines
B Major histocompatibility complex (MHC)
C ADCC
D Antibody
E IL-2
15. An immune response against grass pollen often involves:
A Pathogen-associated molecular patterns (PAMPs)
B Breakdown of self-tolerance
C A hypersensitivity reaction
D Reaction against MHC
E Persistent infection by the pollen
16. Why are secondary antibody responses better?
A They provide defense against unrelated antigens
B The antibody can be made by both T- and B-cells
C Complement-fixing antibodies are made
D They do not require T-cell help
E They are stronger and faster
17. Which cell type produces antibodies?
A Macrophages
B T-lymphocytes
C NK
D Plasma cells
18. What is the single best defining description of the classical pathway of complement activation?
A It acts as a cascade
B It produces a C5 convertase
C In generates the membrane attack complex (MAC)
D It results in the splitting of C3 into C3a and C3b
E It utilizes complement component C1r
19. What is the single best defining feature of a lymphocyte?
A A type of leukocyte
B A cell that is specialized to produce cytokines
C Present in the circulation
D Antigen-specific
E Able to undergo cell proliferation
20. What is the characteristic that best defines the acquired immune response?
A It exhibits immunological memory
B It involves leukocytes
C It involves cell proliferation
D The cells involved recognize pathogens
E It is not present at birth
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