Chapter 4: 4-1 through 4-17

Question 1

What cell produces antibodies once it is activated?

Answer 1

Plasma cells “effector B cells”

Question 2

How is a B cell activated?

Answer 2

binds an antigen, presents to T-cell, Helper T cells stimulates plasma cell to make antibodies that will then tag the antigen for pickup by macrophages or other types of phagocytes.

Question 3

Which of the immunoglobulin isotypes would be most important for neutralizing polio virus before it could infect intestinal cells?
A.  secretory IgA
B.  serum IgA
C.  serum IgD
D.  secretory IgG
E.  Membrane IgM

Answer 3

secretory IgA

Question 4

What are the regions of the antibody contributes MOST to the affinity of the antibody for antigen?
A.  CDR
B.  Fab
C.  Fc
D.  hinge region
E.  loops in the Fc region

Answer 4

CDR

Question 5

What factor or structural element of a antibody determines its isotype form?
A. antigen specificity
B. Heavy chain constant region
C. Light chain constant region
D. number of antigen binding sites
E. number of Variable and constant domains

Answer 5

Heavy chain constant region

Question 6

The _______ contribute to antigen specificity of immunoglobulins, and _______ make up the more conservative flanking regions:
A. hypervariable loops; framework regions
B. constant domains; variable domains
C. heavy chains; light chains
D. variable gene segments; joining gene segments

Answer 6

hypervariable loops; framework regions

Question 7

The derivation of antibodies from a single clone of B lymphocytes that have identical antigen specificity.

Answer 7

Monoclonal antibody production

Question 8

Change of immunoglobulin class but preservation of antigen specificity

Answer 8

isotype switching

Question 9

Nucleotide changes in variable regions of immunoglobulin genes affecting affinity for antigen.

Answer 9

somatic hypermutation

Question 10

Enhancement of receptor-mediated phagocytosis of immunoglobulin-coated antigen.

Answer 10

opsonization

Question 11

The rearrangement of V, D, and J segments to form an immunoglobulin.

Answer 11

somatic recombination

Question 12

Which immunoglobulin’s main function is to mediate 
A.  IgA
B.  IgD
C.  IgE
D.  IgG
E.  IgM

Answer 12

IgE

Question 13

The antigen-binding site of an immunoglobulin is formed from…
A. the V regions of light chains only
B. the C regions of heavy chains only
C. paired V regions of a single heavy chain and a single light chain
D. paired V regions of two light chains
E. paired C regions of two heavy chains

Answer 13

C. paired V regions of a single heavy chain and a single light chain

Question 14

When IgG is cleaved with a protease that targets a hinge region, which of the following is generated?
A. two Fab fragments and one Fc fragment
B. two Fc fragments and two Fab fragments
C. Fc fragments that bind antigen
D. Fab fragments that facilitate antibody effector function
E. a membrane-bound form of antibody

Answer 14

A. two Fab fragments and one Fc fragment

Question 15

The part of the antibody that binds antigen

Answer 15

V domain

Question 16

Contributes around 50 kDa to the overall molecular weight of IgG

Answer 16

heavy chain

Question 17

Comprises the beta strands and loops not involved in antigen binding

Answer 17

framework region

Question 18

The most conserved region of the molecule with limited variation between antibodies

Answer 18

constant region

Question 19

Pairs with the amino-terminal part of a heavy chain to form one of the two arms of an antibody

Answer 19

light chain

Question 20

A protein epitope formed as a result of three-dimensional folding of the protein, and which is destroyed if the protein denatures, is called a \_\_\_\_\_\_\_ epitope.
A.  linear
B.  multivalent
C.  conformational
D.  complementarity
E.  framework

Answer 20

C. conformational

Question 21

The numbered events listed below participated in the generation of junctional diversity. Put them in chronological order.
A. DNA strands pair, and unpaired nucleotides are removed by exonuclease activity.
B. P-nucleotides are generated after nicking of one DNA strand
C. DNA polymerase fills in gaps, and DNA ligation forms a coding joint
D. The RAG complex cleaves heptamer RSSs, and DNA hairpins are formed.
E. Terminal deoxynucleotidyl transferase adds N-nucleotides to the 3 prime end of the stretch of P-nucleotides.

Answer 21

D, B, E, A, C

Question 22

Which of the following statements regarding the process of differential splicing of primary RNA transcripts encoding immunoglobulins is incorrect?
A. It does not require rearrangement of genomic DNA sequences.
B. It underlies the production of both membrane-bound IgM and IgD in naïve B cells.
C. It is the mechanism involved in isotype switching.
D. It occurs during B-cell differentiation into plasma cells when antibodies are produced in their secreted form.
E. It permits the production of different types of protein originating from the same RNA transcript.

Answer 22

C. It is the mechanism involved in isotype switching.

Question 23

located within a V domain and varies greatly between different antibodies

Answer 23

hypervariable region

Question 24

4-7 Which of the following recombinations is not permitted during somatic recombination in the heavy-chain and light-chain immunoglobulin loci? (select all that apply)
A.  Dh:Jh
B.  Vlambda: Jlambda
C.  Dk:Vh
D.  Vh; Jh
E. Vh: Dh

Answer 24

C. Dk:Vh

D. Vh; Jh

Question 25

4-8 Which of the following does not contribute to generating the diversity of antigen-binding specificites amoung immunoglobulins? A. somatic hypermutation B. random combination of heavy and light chains C. somatic recombination D. activation-induced cytidine deaminase (AID) E. alternative splicing of heavy-chain RNRA transcripts.

Answer 25

E. alternative splicing of heavy-chain RNRA transcripts.

Question 26

4-9 The phenomenon of allelic exclusion ensures that B cells... A. use only one V, D, and J segment during somatic recombination. B. express only one type of heavy chain and one type of light chain. C. do not undergo alternative splicing until cell proliferation commences D. do not secrete antibody until antigen is encountered E. carry out affinity maturation directed at heavy chains and not light chains F. derived from B-cell lymphomas are heterogeneous

Answer 26

B. express only one type of heavy chain and one type of light chain.

Question 27

4-10 Which of the IgG subclasses is most efficient at activating complement? Explain why. Which is least efficient and why?

Answer 27

IgG3 is most efficient at complement activation. The hinge region of IgG3 is the longest of all the IgG subclasses. Its length and flexibility mak ethe IgG3 Fc region more accessible for binding C1 compared with the other IgG subclasses. IgG4 fails to activate complement because its Fc regions binds C1 poorly.

Question 28

Which antibody is an opsonin?

Answer 28

IgG, IgA

Question 29

Which antibody has complement activation?

Answer 29

IgA, IgG, IgM

Question 30

Which antibody can be transported across the placenta?

Answer 30

IgG

Question 31

Which antibody is most abundant in serum?

Answer 31

IgG

Question 32

Which antibody is most abundant in mucosal secretions (like colostrum)?

Answer 32

IgA

Question 33

Which antibody has sensitization of mast cells?

Answer 33

IgE, IgG

Question 34

Which antibody has sensitization of basophils?

Answer 34

IgD, IgE

Question 35

Which antibody has sensitization for killing by NK cells?

Answer 35

IgG

Question 36

Which antibody is made in the body more than any other antibody?

Answer 36

IgA

Question 37

Which antibody is least abundant in the serum?

Answer 37

IgE

Question 38

4-12 Humanized monoclonal antibodies are best described as... A. antibodies made in mice in which the mouse antibody genes have been replaced with human equivalents. B. human antibodies in which the CDR loops have been replaced by mouse-derived CDRs of the desired specificity. C. antibodies made in culture by human hybridomas D. antibodies containing mouse Fab regions of both the heavy and light chain and human Fc regions. E. antibodies containing human Fab regions of both the heavy and light chain and mouse Fc regions.

Answer 38

B. human antibodies in which the CDR loops have been replaced by mouse-derived CDRs of the desired specificity.

Question 39

4-13 Which of the IgG subclasses would you think was in principle most desirable for use as a therapeutic monoclonal antibody, and why? Are there any disadvantages to using this subclass and how might they be overcome?

Answer 39

IgG4 would be considered the most desirable in principle because it lacks the ability to activate complement, and so will not trigger complement-mediated inflammation, which could cause damage to the patient. However, the monoclonal IgG4 will swap immunoglobulin chains with the patient's IgG4 at high frequency, thus becoming functionally covalent, compromising its ability to bind as strongly to antigen as the other, stable, IgG subclasses. One solution would be to alter the CH3 region of IgG4 genetically in such a way that it cannot swap heavy:light chain units with other IgG4 antibodies but retains the inability to activate complement.

Question 40

4-14 Which of the following statements best explains why the immune system can continue to make antibodies after treatment with the anti-CD20 antibody rituximab? A. New CD20-positive B cells are reconstituted so quickly that antibody concentration during and after treatment is unaffected. B. Rituximab stimulates B-cell proliferation, so for a short while after its administration there is actually an increase in antibody concentration. C. Rituximab is a mouse monoclonal antibody and therefore its Fc region is unable to bind to the surface receptors on human NK cells that bind to Fc. D. Plasma cells do not express CD20 on their cell surface, and antibody production by these cells continues unhampered. E. Rituximab stimulates anti-antibody production, leading to its rapid clearance by the body.

Answer 40

D. Plasma cells do not express CD20 on their cell surface, and antibody production by these cells continues unhampered.

Question 41

``` 2. IgM and IgD are co-expressed on naive B cells by a process called: A. isotype switching B. somatic recombination C. somatic hypermutation D. alternative mRNA splicing E. affinity maturation ```

Answer 41

D. alternative mRNA splicing

Question 42

``` 3. Enhancement of receptor-mediated phagocytosis of immunoglobulin-coated antigen. A. monoclonal antibodies production B. isotype switching C. somatic hypermutation D. opsonization E. somatic recombination ```

Answer 42

D. opsonization

Question 43

``` 4. Since each B cell productively rearranges a single H and L chain allele, it exhibits? A. Affinity B. Allelic exclusion C. Antibody restriction D. Antigen binding diversity E. Cross reactivity ```

Answer 43

B. Allelic exclusion

Question 44

5. Antibody affinity for antigen depends on: A. the antibody isotype B. The complementary shape and charge of each antibody V region for its antigen epitope C. the number of Fab regions in each antibody molecule D. whether the antibody is in the serum or on the cell surface E. whether the light chains are kappa or lambda

Answer 44

B. The complementary shape and charge of each antibody V region for its antigen epitope