Chapter 6

Question 1

Which of the following cell-surface markers differentiates hematopoietic stem cells from other cell constituents in the bone marrow?

a. pre-B-cell receptor
b. BAFF receptor
c. CD34
d. CD4
e. membrane-bound stem-cell factor (SCF)

Answer 1

CD34

Question 2

Which of the following is characteristic of a large pre-B cell?

a. VDJ is successfully rearranged and μ heavy chain is made.
b. V–J is rearranging at the light-chain locus.
c. μ heavy chain and λ or κ light chain is made.
d. V is rearranging to DJ at the heavy-chain locus.
e. D–J is rearranging at the heavy-chain locus.

Answer 2

VDJ is successfully rearranged and μ heavy chain is made.

Question 3

Which of the following statements is correct?

a. The κ light-chain genes rearrange before the heavy-chain genes.
b. The κ light-chain genes rearrange before the λ light-chain genes.
c. The λ light-chain genes rearrange before the heavy-chain genes.
d. The λ light-chain genes rearrange before the κ light-chain genes.
e. The μ heavy-chain genes rearrange first and then the λ light-chain genes rearrange.

Answer 3

The κ light-chain genes rearrange before the λ light-chain genes.

Question 4

Immature B cells develop into B cells in the

a. subendosteum
b. bone marrow
c. thymus
d. blood
e. secondary lymphoid organs

Answer 4

secondary lymphoid organs

Question 5

Place the following phases of a B cell’s life history in the correct chronological order.

a. negative selection
b. attacking infection
c. finding infection
d. searching for infection
e. repertoire assembly
f. positive selection

Answer 5

e. repertoire assembly
a. negative selection
f. positive selection
d. searching for infection
c. finding infection
b. attacking infection

Question 6

Place the following stages of B-cell development in the correct chronological order.

a. early pro-B cell
b. large pre-B cell
c. immature B cell
d. stem cell
e. late pro-B cell
f. small pre-B cell

Answer 6

d. stem cell
a. early pro-B cell
e. late pro-B cell
b. large pre-B cell
f. small pre-B cell
c. immature B cell

Question 7

Large pre-B cells are characterized by which of the following?

a. They do not express CD19 at the cell surface.
b. Rearrangement of light-chain genes commences.
c. Nonproductive rearrangement of both heavy-chain loci has already occurred.
d. Allelic exclusion of the immunoglobulin light-chain loci has already occurred.
e. μ is assembled with VpreBλ5.

Answer 7

μ is assembled with VpreBλ5.

Question 8

All hematopoietic stem cells express

a. CD34
b. CD127
c. CD19
d. VpreBλ5
e. Pax-5

Answer 8

CD34

Question 9

Which of the following do not associate with one another during B-cell development?

a. IL-7: IL-7 receptor of late pro-B cells
b. Pax-5: CD19 gene
c. surrogate light chain: δ heavy chain
d. VpreB: λ5
e. SCF: Kit
f. pre-B-cell receptor: Igα and Igβ

Answer 9

surrogate light chain: δ heavy chain

Question 10

The latest stages of late pro-B-cell development are recognized by the association of a surrogate light chain with a μ chain. The surrogate light chain is composed of

a. E2A and EFB
b. Igα and Igβ
c. VpreB and λ5
d. RAG-1 and RAG-2
e. Pax-5 and CD19

Answer 10

VpreB and λ5

Question 11

A genetic defect in the λ5 gene would cause which of the following consequences? (Select all that apply.)

a. inability to produce functional μ chains
b. inability to produce a pre-B-cell receptor
c. inability to produce functional κ or λ chains
d. production of different light chains owing to defects in allelic exclusion
e. B-cell immunodeficiency
f. chronic bacterial infections
g. requirement for prophylactic injections of antibodies from healthy donors

Answer 11

b. inability to produce a pre-B-cell receptor
e. B-cell immunodeficiency
f. chronic bacterial infections
g. requirement for prophylactic injections of antibodies from healthy donors

Question 12

Which of the following is not paired with its correct complement?

a. N nucleotides: more abundant in rearranged heavy-chain genes than in rearranged light-chain genes
b. second checkpoint in B-cell development: assembly of a functional B-cell receptor
c. receptor editing: exchange of light chain for one that is not self-reactive
d. first checkpoint in B-cell development: selection by the pre-B-cell receptor
e. large pre-B-cell stage: constitutive expression of RAG-1 and RAG-2 proteins

Answer 12

large pre-B-cell stage: constitutive expression of RAG-1 and RAG-2 proteins

Question 13

Which of the following would occur after the production of a functional μ chain as a pre-B-cell receptor?

a. RAG proteins are degraded.
b. The chromatin structure of the heavy-chain locus is reorganized to prevent gene rearrangement.
c. Transcription of the RAG1 and RAG2 genes ceases.
d. There is allelic exclusion of a second μ chain.
e. All of the above would occur.

Answer 13

All of the above would occur.

Question 14

An important advantage of having two gene loci (κ and λ) for the light chain is

a. that the likelihood of a successful rearrangement of light-chain genes increases.
b. that immunoglobulins are homogeneous and not heterogeneous in mature B cells.
c. that different effector functions are conferred by the two different light-chain loci.
d. that surrogate light-chain transcription cannot compete with κ and λ transcription and enables B-cell development.
e. all of the above.

Answer 14

that the likelihood of a successful rearrangement of light-chain genes increases.

Question 15

Which of the following is correctly matched? (Select all that apply.)

a. early pro-B cell: VDJ rearranged
b. pre-B-cell receptor: VpreBλ5/μu heavy chain
c. mature B cell: IgM plus IgD
d. small pre-B cell: VJ rearranged
e. immature B cell: μ heavy chain plus λ or κ light chain on surface

Answer 15

b. pre-B-cell receptor: VpreBλ5/μu heavy chain
c. mature B cell: IgM plus IgD
e. immature B cell: μ heavy chain plus λ or κ light chain on surface

Question 16

Large pre-B cells undergo clonal expansion before the rearrangement of light-chain loci. Which of the following are beneficial consequences of clonal expansion? (Select all that apply.)

a. Autoreactive B cells are eliminated before the expenditure of energy needed to rearrange a functional light-chain gene.
b. The energy used to make a functional heavy chain is not wasted as a result of the inability to produce a functional light chain.
c. RAG gene expression is decreased, which in turn signals light-chain rearrangement.
d. A diverse population of immature B cells is generated that express the same μ chain but a distinct light chain.
e. Approximately 85% of small pre-B cells will progress to the immature B-cell stage.

Answer 16

b. The energy used to make a functional heavy chain is not wasted as a result of the inability to produce a functional light chain.
d. A diverse population of immature B cells is generated that express the same μ chain but a distinct light chain.
e. Approximately 85% of small pre-B cells will progress to the immature B-cell stage.

Question 17

When expression of _______ is turned off in small pre-B cells, the result is the presence of P nucleotides but an absence of N nucleotides in around 50% of light-chain genes.

a. Kit
b. CD19
c. TdT
d. Pax-5
e. RAG-1 and RAG-2

Answer 17

TdT

Question 18

A defect in which of the following proteins blocks B-cell development at the pre-B-cell stage, resulting in almost no circulating antibodies in individuals with this defect?

a. IL-7 receptor
b. terminal deoxynucleotidyltransferase (TdT)
c. Pax-5
d. Bruton’s tyrosine kinase (Btk)
e. CD19

Answer 18

Bruton’s tyrosine kinase (Btk)

Question 19

The consequence of allelic exclusion at the immunoglobulin loci ensures that _____. (Select all that apply.)

a. B-cell receptors have a low-avidity binding
b. B cells express antigen receptors of a single specificity
c. hybrid immunoglobulins are formed
d. all functional copies of a gene are expressed
e. homogeneous B-cell receptors bind more effectively to antigen

Answer 19

b. B cells express antigen receptors of a single specificity

e. homogeneous B-cell receptors bind more effectively to antigen

Question 20

A developing B cell unable to generate a productive rearrangement on any of the four light-chain loci will undergo

a. self-renewal
b. apoptosis
c. allelic exclusion
d. malignant transformation
e. differentiation into a B-1 cell

Answer 20

apoptosis

Question 21

All of the following participate in signal transduction in developing B cells except

a. terminal deoxynucleotidyl transferase (TdT)
b. FLT3
c. CD19
d. Igα and Igβ
e. Bruton’s tyrosine kinase (Btk)
f. CD45

Answer 21

terminal deoxynucleotidyl transferase (TdT)

Question 22

Negative selection of developing B cells ensures that

a. there is not an overabundance of circulating B cells that would compete with other important cell types in the circulation
b. only antigen-activated B cells leave the bone marrow
c. clonal expansion of B cells does not occur in the absence of infection
d. B-cell receptors that bind to normal constituents of the body do not emerge
e. B cells do not leave secondary lymphoid tissues

Answer 22

B-cell receptors that bind to normal constituents of the body do not emerge

Question 23

Receptor editing occurs _____. (Select all that apply.)

a. in the bone marrow
b. after encounter with foreign antigen in secondary lymphoid organs
c. in mature B cells
d. to establish self-tolerance of the B-cell repertoire
e. to express an excess of IgM over IgD on the surface of mature B cells

Answer 23

a. in the bone marrow

d. to establish self-tolerance of the B-cell repertoire

Question 24

Which of the following statements about the IgD made by B cells of upper respiratory mucosa is not true?

a. These antibodies bind to airborne bacteria such as Haemophilus influenzae.
b. λ light chains are used almost exclusively by these IgD antibodies.
c. Two-thirds of these IgD antibodies possess κ light chains.
d. These IgD antibodies recruit basophils and induce the secretion of antibacterial peptides.

Answer 24

Two-thirds of these IgD antibodies possess κ light chains.

Question 25

Individuals who fail to express functional Bruton’s tyrosine kinase exhibit all of the following characteristics except

a. B-cell development is blocked at the immature B-cell stage.
b. They are usually male because the Btk gene is on the X chromosome.
c. They suffer from an immune deficiency known as X-linked agammaglobulinemia (XLA).
d. Recurrent infections with extracellular bacteria are common.
e. They benefit from treatment with immunoglobulin infusions.

Answer 25

B-cell development is blocked at the immature B-cell stage.

Question 26

All of the following are associated with the development of Burkitt’s lymphoma except

a. The expression of Myc protein is perturbed.
b. A chromosomal translocation involving a proto-oncogene and an immunoglobulin gene occurs.
c. Overproduction of the Bcl-2 protein prolongs the lifetime of B-lineage cells.
d. Cell division restraints on mutated B cells are lifted.
e. In addition to a chromosomal translocation event, mutations elsewhere in the genome are usually involved.

Answer 26

Overproduction of the Bcl-2 protein prolongs the lifetime of B-lineage cells.

Question 27

Which of the following is a characteristic of B-2 cells?

a. They are sometimes referred to as CD5 B cells.
b. They comprise only 5% of the B-cell repertoire.
c. In adults, they are renewed by cell division in the peripheral circulation.
d. They are located primarily in secondary lymphoid organs.
e. They are not dependent on T helper cells for activation.

Answer 27

They are located primarily in secondary lymphoid organs.

Question 28

Identify the mismatched pair of chemokine and the cells that secrete it.

a. CCL19: lymph-node dendritic cells
b. CXCL13: follicular dendritic cells
c. CCL21: stromal cells of secondary lymphoid tissues
d. All of the above are correctly matched

Answer 28

All of the above are correctly matched

Question 29

Plasma cells have all of the properties listed except

a. they rapidly proliferate in secondary lymphoid follicles
b. they secrete antibody
c. they are terminally differentiated B cells
d. they no longer express MHC class II molecules
e. they cease expressing membrane-bound immunoglobulin
f. they differentiate into plasma cells after migration from germinal centers to other sites in lymphoid tissue and bone marrow

Answer 29

they rapidly proliferate in secondary lymphoid follicles

Question 30

All of the following events occur within germinal centers except

a. centrocytes mature from centroblasts
b. isotype switching
c. centroblasts arise from activated B ells
d. B cells are activated by CD4 helper T cells
e. affinity maturation
f. somatic hypermutation
g. production of memory B cells

Answer 30

B cells are activated by CD4 helper T cells

Question 31

In which location would plasma cells not be present?

a. bone marrow
b. afferent lymphatic vessels
c. medullary cords of lymph nodes
d. lamina propria of gut-associated lymphoid tissues
e. red pulp of spleen
f. efferent lymphatic vessels

Answer 31

afferent lymphatic vessels

Question 32

Which of the following is true of centrocytes? (Select all that apply.)

a. Somatic hypermutation has occurred.
b. They are large proliferating cells.
c. Isotype switching is complete.
d. They produce secreted forms of immunoglobulins.
e. They lack MHC class II molecules on the cell surface.

Answer 32

a. Somatic hypermutation has occurred.

c. Isotype switching is complete.

Question 33

Immunological tolerance in the B-cell repertoire is called _______ tolerance when it develops in primary lymphoid organs, and _______ tolerance when it is induced outside the bone marrow.

a. primary; secondary
b. apoptotic; anergic
c. stromal; follicular
d. receptor-mediated; systemic
e. central; peripheral

Answer 33

central; peripheral

Question 34

A plasma cell is characterized by which of the following features? (Select all that apply.)

a. It differentiates in the medulla of lymph nodes and the bone marrow.
b. It dedicates 10–20% of total protein synthesis to antibody production.
c. Levels of MHC class II molecules are elevated.
d. It undergoes extensive proliferation in germinal centers.
e. It produces secreted immunoglobulin instead of the membrane-bound form.

Answer 34

a. It differentiates in the medulla of lymph nodes and the bone marrow.
b. It dedicates 10–20% of total protein synthesis to antibody production.
e. It produces secreted immunoglobulin instead of the membrane-bound form.

Question 35

When producing monoclonal antibodies, why is it important to use as a fusion partner a myeloma cell that is unable to produce its own immunoglobulin?

a. to ensure that allelic exclusion of μ chain occurs normally
b. to ensure that the antibodies are homogeneous and able to make strong bivalent attachments to multivalent antigens
c. to ensure that the monoclonal antibodies are not autoreactive
d. to provide a greater opportunity for making a successful rearrangement at the light-chain locus
e. to ensure that antibodies are secreted and not membrane-bound

Answer 35

to ensure that the antibodies are homogeneous and able to make strong bivalent attachments to multivalent antigens

Question 36

The proto-oncogene _______ is associated with the development of Burkitt’s lymphoma.

a. BCL-2
b. Myc
c. CD5
d. CD19
e. BTK

Answer 36

Myc

Question 37

Which of the following characterizes the B-1 cells that develop prenatally?

a. They lack N nucleotides.
b. They possess polyspecificity for bacterial polysaccharide antigens.
c. They arise early in embryonic development preceding the development of the majority subset of B cells.
d. They have little or no IgD on the cell surface.
e. All of the above.

Answer 37

All of the above.

Question 38

What is the fate of an immature B cell that encounters and has specificity for self antigen?

a. If further heavy-chain and light-chain gene rearrangements are possible, it undergoes apoptosis.
b. Somatic hypermutation.
c. Decrease in production of IgD.
d. Continued rearrangement of heavy-chain genes.
e. Continued rearrangement of light-chain genes.

Answer 38

Continued rearrangement of light-chain genes.

Question 39

Which of the following pertains to the fate of immature B cells that have specificity for univalent self antigens? (Select all that apply.)

a. The cells acquire a state of unresponsiveness called anergy.
b. IgD is retained in the cytosol.
c. IgD on the cell surface fails to activate the B cell when bound to self antigen.
d. The cells have a much longer life-span than mature B cells.
e. The cells die by apoptosis.

Answer 39

a. The cells acquire a state of unresponsiveness called anergy.
c. IgD on the cell surface fails to activate the B cell when bound to self antigen.

Question 40

The circulatory route through a lymphoid tissue for both immature B cells and mature B cells that do not encounter specific antigen is:

a. bloodstream →HEV of lymphoid cortex → primary lymphoid follicle → efferent lymphatic vessel
b. afferent lymphatic vessel → primary lymphoid follicle →HEV of lymphoid cortex →efferent lymphatic vessel
c. afferent lymphatic vessel →medullary cords → primary lymphoid follicle →efferent lymphatic vessel
d. primary lymphoid follicle →HEV of lymphoid cortex →afferent lymphatic vessel →efferent lymphatic vessel
e. bloodstream →afferent lymphatic vessel → HEV of lymphoid cortex →efferent lymphatic vessel

Answer 40

bloodstream →HEV of lymphoid cortex → primary lymphoid follicle → efferent lymphatic vessel

Question 41

What would be the consequence if a defective signaling component of the pre-B-cell receptor resulted in continuing high-level RAG gene transcription?

a. Heterogeneous B-cell receptors would be expressed on the cell surface.
b. Each heavy-chain locus would rearrange repeatedly until only the outermost V and J segments were combined, thus significantly reducing immunoglobulin diversity.
c. Other genomic segments would be rearranged, resulting in death of the B cell.
d. The light-chain locus would not rearrange.

Answer 41

Heterogeneous B-cell receptors would be expressed on the cell surface.

Question 42

Systemic lupus erythematosus (SLE) is an autoimmune disease in which damage to small blood vessels occurs when immune complexes of self antigens and autoreactive antibodies form and deposit there. The self antigens include DNA, RNA, and components of nucleoprotein particles. Which of the following explains why self-reactive B cells in SLE have escaped immunological tolerance?

a. Individuals with SLE have an immunodeficiency that disrupts self-tolerance.
b. Self-tolerance operates only in the early years of one’s lifetime.
c. Self-tolerance is readily induced to accessible self antigens, but not to inaccessible self antigens.
d. Self-tolerance is not efficient when self antigens are abundant and systemically distributed.

Answer 42

Self-tolerance is readily induced to accessible self antigens, but not to inaccessible self antigens.

Question 43

What is the normal situation whereby the immune system does not respond to self antigens?

a. positive selection
b. self-tolerance
c. immunodeficiency
d. autotrophic responses

Answer 43

self-tolerance

Question 44

A complete and functional immunoglobulin chain is made only if what circumstance occurs?

a. The number of nucleotides added at the junctions between V, D, and J segments is an even number.
b. A correct reading frame in the variable region is produced.
c. All three reading frames of immunoglobulin genes are used during transcription.
d. The intervening gene segments are excised from the genome.

Answer 44

A correct reading frame in the variable region is produced.

Question 45

Assume that an early pro-B cell has productively rearranged D to J segments on both chromosomes. What happens if there is then a nonproductive V–DJ rearrangement of the heavy-chain locus on the first chromosome?

a. Terminal deoxynucleotidyl transferase (TdT) adds additional nucleotides at the junctions between V and D.
b. A second rearrangement occurs on the first chromosome involving only V and J segments.
c. The pro-B cell is signaled to die by apoptosis.
d. Rearrangement of V–DJ occurs on the second chromosome.

Answer 45

Rearrangement of V–DJ occurs on the second chromosome.

Question 46

Order the steps of how B cells circulate through a lymph node.
efferent lymphatic vessel
blood
T-cell area to medullary cords
high endothelial venule
T-cell area
primary lymphoid follicle

Answer 46

blood
high endothelial venule
T-cell area
primary lymphoid follicle
T-cell area to medullary cords
efferent lymphatic vessel

Question 47

Which of the following occurs in the subendosteum region of the bone marrow?

a. Late pro-B cells accumulate while completing rearrangement of heavy-chain genes there.
b. Immature B cells are exported to the circulation from there.
c. Small pre-B cells initiate the rearrangement of light-chain genes there.
d. A high proportion of hematopoietic stem cells reside there.

Answer 47

A high proportion of hematopoietic stem cells reside there.

Question 48

Immature B cells that pass the self-tolerance test are identified by the coexpression of IgM and IgD. What process allows this to occur?

a. isotype switching to Cδ, providing a short window of time for both IgM and IgD to be on the cell surface simultaneously
b. alternative splicing of the heavy-chain mRNA
c. the utilization of different promoter sequences flanking either Cμ or Cδ
d. rearrangement of the heavy-chain locus on the second chromosome

Answer 48

alternative splicing of the heavy-chain mRNA

Question 49

What happens when B lymphocytes become inactivated and unresponsive to their specific antigen?

a. They undergo allelic exclusion.
b. They enter a state of anergy.
c. They die through apoptosis.
d. They begin the process of receptor editing.

Answer 49

They enter a state of anergy.

Question 50

What occurs following cell division of large pre-B cells?

a. Rearrangement of the second heavy-chain locus occurs.
b. The surrogate light chain is synthesized.
c. The pre-B-cell receptor transduces survival signals.
d. μ chains are synthesized and remain inside the cell.

Answer 50

μ chains are synthesized and remain inside the cell.

Question 51

Where do isotype switching, somatic hypermutation, and affinity maturation occur?

a. bone marrow
b. germinal center
c. T-cell area
d. primary lymphoid follicle

Answer 51

germinal center

Question 52

What happens if the B-cell receptor of an immature B cell does not interact with multivalent self antigens present in the bone marrow?

a. The cell alters its B-cell receptors.
b. The cell arrests its developmental progression.
c. The cell is exported to the peripheral circulation as an immature B cell.
d. The cell becomes a mature B cell and then enters the peripheral circulation.

Answer 52

The cell is exported to the peripheral circulation as an immature B cell.

Question 53

Identify the following as characteristics of either B-1 or B-2 cells.

a. They are first produced after birth.
b. They are replenished through self-renewal and mitosis.
c. They are dependent on T-cell help to become activated.
d. They produce few, if any, memory B cells.
e. They have a diverse repertoire of V regions.

Answer 53

B-2 Characteristics

a. They are first produced after birth.
c. They are dependent on T-cell help to become activated.
e. They have a diverse repertoire of V regions.

B-1 Characteristics

b. They are replenished through self-renewal and mitosis.
d. They produce few, if any, memory B cells.

Question 54

You are a researcher interested in learning more about B-cell anergy. You would like to obtain a B-cell line from a tumor that has a single receptor specificity and resembles a naive B cell. Which tumor type would most likely serve your needs?

a. acute lymphoblastic leukemia (ALL)
b. multiple myeloma
c. mantle cell lymphoma
d. Hodgkin’s lymphoma

Answer 54

mantle cell lymphoma

Question 55

The second checkpoint in B-cell development that tests the quality of the light chain occurs at what stage?

a. small pre-B cell
b. mature B cell
c. early pro-B cell
d. immature B cell

Answer 55

small pre-B cell

Question 56

An individual presents in the clinic with complaints of general achiness and fatigue. When her blood is checked for infection, it is found that her antibodies are overwhelmingly targeting a single antigen. What would you expect to find in her B-cell populations?

a. a repertoire of normal depth and breadth
b. clonal population derived from a single ancestral cell
c. circulating pro-B cells
d. only cells that express IgM isotypes

Answer 56

clonal population derived from a single ancestral cell

Question 57

Upon reaching what stage is a developing B cell irreversibly committed to the B-cell lineage?

a. pro-B cell
b. immature B cell
c. pre-B cell
d. pluripotent hematopoietic stem cell

Answer 57

pro-B cell

Question 58

The first checkpoint in B-cell development that tests the quality of the μ chain occurs at what stage?

a. large pre-B cell
b. early pro-B cell
c. small pre-B cell
d. late pro-B cell

Answer 58

late pro-B cell

Question 59

Immediately after activated B cells have migrated to primary follicles, they do what?

a. become proliferating centroblasts
b. secrete immunoglobulin
c. become anergic and leave secondary lymphoid organs
d. die by apoptosis

Answer 59

become proliferating centroblasts

Question 60

B-cell development is divided into six functionally distinct phases. Place the phases in chronological order.

a. positive selection
b. attacking infection
c. finding infection
d. repertoire assembly
e. searching for infection
f. negative selection

Answer 60

d. repertoire assembly
f. negative selection
a. positive selection
e. searching for infection
c. finding infection
b. attacking infection

Question 61

In contrast to peripheral tolerance, central tolerance has what result?

a. It induces a stage of anergy in self-reactive B cells.
b. It signals continuation of light-chain gene rearrangement.
c. It causes death of self-reactive B cells by apoptosis.
d. It occurs in the circulation.

Answer 61

It signals continuation of light-chain gene rearrangement.

Question 62

Why are the immunoglobulin loci in non-B cells transcriptionally silent?

a. Antigen recognition by and signal transduction through the B-cell receptor does not occur.
b. Gene rearrangement of these loci has not occurred.
c. Pax-5 is not made in those cells.
d. Non-B cells do not express components of the surrogate light chain.

Answer 62

Pax-5 is not made in those cells.

Question 63

Which molecule do all human hematopoietic stem cells express?

a. CD19
b. CD34
c. CD127
d. CD10

Answer 63

CD34

Question 64

What aids the attraction of B cells from the T-cell area to the primary lymphoid follicle?

a. CCR7
b. CXCL13
c. CCL21
d. CCL19

Answer 64

CXCL13

Question 65

What is the name given to the specialized cell type that helps to form the supporting framework required for B-cell development?

a. lymphatic endothelial cell
b. stromal cell
c. hematopoietic cell
d. helper T cell

Answer 65

stromal cell

Question 66

Although the pre-B-cell receptor resembles the B-cell receptor, it differs by containing a surrogate light chain that is composed of what?

a. Igα and Igβ
b. only the variable region of κ light chains
c. VpreB and λ5
d. E2A and E2B

Answer 66

VpreB and λ5

Question 67

In B-cell development, what is it called when the quality of the immunoglobulin chains arising from gene rearrangement is tested?

a. clonal expansion
b. checkpoint
c. pre-B-cell editing
d. successive rearrangement
e. allelic exclusion

Answer 67

checkpoint

Question 68

Which of the following cell types express CD5?

a. B-1 cells
b. all mature B cells
c. T cells
d. B-2 cells

Answer 68

a. B-1 cells

c. T cells

Question 69

RNA tumor viruses that directly mediate the development of cancer in their vertebrate hosts contain oncogenes originating from what phenomenon?

a. a reciprocal chromosomal translocation between host and viral genomes
b. rearrangement events in the viral genome involving a mechanism similar to somatic recombination
c. a virus that has accumulated multiple mutations in viral genes that affect host-cell growth
d. the genome of the host

Answer 69

the genome of the host

Question 70

Which of the following is a type of B-cell tumor that arises from a germinal center B cell and does not express antigen receptor?

a. follicular center cell lymphoma
b. multiple myeloma
c. Hodgkin’s lymphoma
d. acute lymphoblastic leukemia (ALL)

Answer 70

Hodgkin’s lymphoma

Question 71

What happens to immature B cells whose B-cell receptors bind soluble monovalent self antigens?

a. They remain in the bone marrow.
b. They are rendered anergic.
c. They may be rescued by light-chain rearrangement.
d. They die by apoptosis.

Answer 71

They are rendered anergic.

Question 72

What drives changes in the expression of proteins that facilitate gene rearrangement of immunoglobulin loci during B-cell development?

a. transcription factors
b. cell proliferation
c. differentiation markers
d. checkpoints

Answer 72

transcription factors

Question 73

Which of the following is associated with developing B cells but not developing T cells?

a. RAG-1 and RAG-2 proteins
b. terminal deoxynucleotidyl transferase (TdT)
c. Pax-5
d. D segments

Answer 73

Pax-5

Question 74

What is the name of the site where activated B cells undergo significant cell division?

a. bone marrow
b. medullary cords
c. T-cell area
d. germinal center

Answer 74

germinal center

Question 75

What happens if, after exhausting the receptor-editing process in the bone marrow, a given B cell produces a receptor that binds to multivalent self antigen?

a. The cell is exported to the periphery, where it is subjected to the next checkpoint in its development.
b. The cell diverts its development to an alternative cell-lineage pathway.
c. The immature B cell exchanges a self-reactive heavy chain for one that is not self-reactive.
d. The cell dies by apoptosis in the bone marrow.

Answer 75

d. The cell dies by apoptosis in the bone marrow.

Question 76

Where do B cells complete their maturation?

a. in secondary lymphoid tissue
b. in the bloodstream
c. at the sites of infection
d. in the bone marrow

Answer 76

in secondary lymphoid tissue

Question 77

Which of the following occurs in the subendosteum region of the bone marrow?

a. A high proportion of hematopoietic stem cells reside there.
b. Late pro-B cells accumulate while completing rearrangement of heavy-chain genes there.
c. Immature B cells are exported to the circulation from there.
d. Small pre-B cells initiate the rearrangement of light-chain genes there.

Answer 77

A high proportion of hematopoietic stem cells reside there.

Question 78

What does receptor editing affect?

a. only heavy-chain genes
b. both heavy- and light-chain genes
c. the mRNA transcripts of immunoglobulin genes, not the genes themselves
d. only light-chain genes

Answer 78

only light-chain genes

Question 79

In transformed B cells of individuals with Burkitt’s lymphoma, where are the chromosomal sites of breakage and rejoining found?

a. within the light-chain loci
b. in a viral oncogene and an immunoglobulin gene
c. in the proto-oncogene MYC and an immunoglobulin gene
d. in the proto-oncogene BCL2 and an immunoglobulin gene

Answer 79

in the proto-oncogene MYC and an immunoglobulin gene

Question 80

What is the replacement of a self-reactive antigen receptor with a non-self-reactive receptor in developing B cells called?

a. receptor editing
b. allelic exclusion
c. positive selection
d. alternative splicing

Answer 80

receptor editing

Question 81

What happens if an immature B cell binds to a multivalent self antigen after the cell has emerged from the bone marrow?

a. It dies by apoptosis or becomes inactivated.
b. It becomes a mature B cell.
c. It differentiates into a plasma cell.
d. It undergoes cell division, a process called clonal expansion.

Answer 81

It dies by apoptosis or becomes inactivated.

Question 82

Which of the following two chromosomes are joined in translocations observed in cases of Burkitt’s lymphoma?

a. 14 and 2
b. 8 and 22
c. 14 and 22
d. 2 and 22

Answer 82

8 and 22

Question 83

Which of the following refers to events that join DNA sequences from two different chromosomes?

a. productive rearrangement
b. translocation
c. gene rearrangement
d. nonproductive rearrangement

Answer 83

translocation

Question 84

A patient with mutations in both alleles of the gene for λ5 was the subject of a case study. The maternal allele carried a stop codon in exon 1 of the gene causing premature termination of translation. The paternal allele, believed to have originated from a gene-conversion event, contained three base-pair substitutions in exon 3 that corresponded with the sequence in the nonfunctional λ5 pseudogene. Flow-cytometric analysis of bone marrow B-cell precursors showed only 6% of cells were CD19+ (compared with 46% in the control) and only 0.7% were positive for surface immunoglobulin (compared with 29% in the control). In addition, only 85% of the CD19+ cells expressed CD34, indicative of a block in transition between the pro-B-cell and pre-B-cell stages of development. The long-term management regimen for this patient included intravenous immunoglobulin replacement and prophylactic and therapeutic antibiotics with careful monitoring of antibiotic efficacy at times of infection. Which of the following best explains the underlying cause of the profound B-cell immunodeficiency detected in this patient?

a. inability to signal cessation of heavy-chain gene rearrangement, causing production of high levels of self-reactive receptors that induce apoptosis of autoreactive developing B cells
b. The developing B cells die by apoptosis at the pro-B-cell stage.
c. inability of developing B cells to produce productive VDJ rearrangements in the heavy-chain genes, causing late pro-B cells to die by apoptosis
d. Transcription of genes encoding Igα and Igβ requires the transcription factor λ5. The pre-B-cell receptor cannot form without Igα/Igβ and in its absence fails to produce the survival signal needed to complete B-cell development.

Answer 84

The developing B cells die by apoptosis at the pro-B-cell stage.

Question 85

A B cell expresses only one of its two copies of an immunoglobulin gene. What is this called?

a. passive immunity
b. allelic exclusion
c. nonproductive rearrangement
d. immature development

Answer 85

allelic exclusion