Chapter 7 Flashcards

1
Q

In which of the following ways does the developmental pathway of α:β T cells differ from that of B cells? (Select all that apply.)

a. Their antigen receptors are derived from gene rearrangement processes.
b. When the first chain of the antigen receptor is produced it combines with a surrogate chain.
c. Cells bearing self-reactive antigen receptors undergo apoptosis.
d. MHC molecules are required to facilitate progression through the developmental pathway.
e. T cells do not rearrange their antigen-receptor genes in the bone marrow.

A

d. MHC molecules are required to facilitate progression through the developmental pathway.
e. T cells do not rearrange their antigen-receptor genes in the bone marrow.

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2
Q

Which of the following cell-surface glycoproteins is characteristic of stem cells, but stops being expressed when a cell has committed to the T-cell developmental pathway?

a. CD2
b. CD3
c. CD25
d. CD34
e. MHC class II

A

CD34

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3
Q

Which of the following processes is not dependent on an interaction involving MHC class I or class II molecules? (Select all that apply.)

a. positive selection of α:β T cells
b. intracellular signaling by pre-T-cell receptors
c. negative selection of αβ T cells
d. peripheral activation of mature naive T cells
e. positive selection of γ:δ T cells

A

b. intracellular signaling by pre-T-cell receptors

e. positive selection of γ:δ T cells

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4
Q

If a double-negative thymocyte has just completed a productive β-chain gene rearrangement, which of the following describes the immediate next step in the development of this thymocyte?

a. A pre-T-cell receptor is assembled as a superdimer.
b. Rearrangement of γ- and δ-chain genes commences.
c. Expression levels of RAG-1 and RAG-2 are elevated.
d. The linked δ-chain genes are eliminated.
e. This cell will inevitably differentiate into a committed γ:δ T cell.

A

A pre-T-cell receptor is assembled as a superdimer.

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5
Q

All of the following cell-surface glycoproteins are expressed by double-negative thymocytes undergoing maturation in the thymus except _____. (Select all that apply.)

a. CD2
b. CD5
c. CD127 (IL-7 receptor)
d. CD34
e. CD1A
f. CD4

A

d. CD34

f. CD4

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6
Q

_____ is a T-cell-specific adhesion molecule expressed before the expression of a functional T-cell receptor while the thymocytes are still in their double-negative stage of development.

a. CD4
b. CD8
c. CD25
d. CD2
e. CD3

A

CD2

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7
Q

Which of the following is mismatched:

a. double-negative CD3– thymocytes: cortico-medullary junction
b. double-negative CD3– thymocytes: subcapsular zone
c. double-positive CD3+ thymocytes: cortico-medullary junction
d. cortical epithelial cells: subcapsular regions
e. dendritic cells: cortico-medullary junction

A

double-negative CD3– thymocytes: cortico-medullary junction

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8
Q

After interaction with thymic stromal cells, _____, a glycoprotein not expressed by the uncommitted progenitor cell is activated in developing thymocytes. (Select all that apply.)

a. CD2
b. CD34
c. CD5
d. CD127 (IL-7 receptor)
e. CD44

A

a. CD2
c. CD5
d. CD127 (IL-7 receptor)

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9
Q

Which of the following statements about Notch 1 is correct? (Select all that apply.)

a. Notch 1 is expressed on thymic epithelial cells.
b. In the absence of Notch 1 expression, T cells can complete their differentiation.
c. Notch 1 is to T-cell development as Pax-5 is to B-cell development.
d. Notch 1 contains two distinct domains, one of which is proteolytically cleaved and becomes a transcription factor in the nucleus.
e. The extracellular domain of Notch 1 must interact with a ligand on thymic epithelium to initiate cleavage and separation of the Notch 1 extracellular and intracellular domains.

A

c. Notch 1 is to T-cell development as Pax-5 is to B-cell development.
d. Notch 1 contains two distinct domains, one of which is proteolytically cleaved and becomes a transcription factor in the nucleus.
e. The extracellular domain of Notch 1 must interact with a ligand on thymic epithelium to initiate cleavage and separation of the Notch 1 extracellular and intracellular domains.

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10
Q

Which of the following is the first stage of T-cell receptor gene rearrangement in α:β T cells?

a. Vα→Dα
b. Dα →Jα
c. Vβ→ Dβ
d. Dβ→Jβ
e. Vα→Jα

A

Dβ→Jβ

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11
Q

Which of the following is the first T-cell receptor complex containing the β chain to reach the cell surface during the development of T lymphocytes?

a. γ:β:CD3
b. β:CD3
c. α:β:CD3
d. β:CD44
e. pTα:β:CD3

A

pTα:β:CD3

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12
Q

Genetic deficiencies in all of the following would impair the development of a fully functional T-cell repertoire except

a. RAG-1 or RAG-2
b. Notch1
c. Pax-5
d. IL-7 receptor (CD127)
e. TAP-1 or TAP-2

A

Pax-5

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13
Q

There are many parallels between the development of B cells and T cells. Identify the incorrectly matched counterpart in B cells (left) versus T cells (right).

a. VpreBλ5: pTα
b. Igα/Igβ:CD3
c. Pax-5: FoxP3
d. multiple κ and λ light-chain gene rearrangements: multiple α-chain gene rearrangements

A

Pax-5: FoxP3

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14
Q

Which of the following statements are true of a T cell that expresses two α chains (and thus two different T-cell receptors) as a result of ineffective allelic exclusion of the α chain during rearrangement? (Select all that apply.)

a. Engaging either of the T-cell receptors on MHC molecules of the thymic epithelium will result in positive selection.
b. One of the T-cell receptors will be functional while the other will most probably be non-functional.
c. If either T-cell receptor binds strongly to self-peptides presented by self-MHC molecules, the thymocyte will be negatively selected.
d. One of the T-cell receptors may be autoreactive but escape negative selection because its peptide antigen is present in tissues other than the thymus.
e. Subsequent gene rearrangements may give rise to a γ:δ T-cell receptor.

A

a. Engaging either of the T-cell receptors on MHC molecules of the thymic epithelium will result in positive selection.
b. One of the T-cell receptors will be functional while the other will most probably be non-functional.
c. If either T-cell receptor binds strongly to self-peptides presented by self-MHC molecules, the thymocyte will be negatively selected.
d. One of the T-cell receptors may be autoreactive but escape negative selection because its peptide antigen is present in tissues other than the thymus.

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15
Q

Once a thymocyte has productively rearranged a β-chain gene, which of these event(s) can occur subsequently? (Select all that apply.)

a. β binds to pTα and is expressed on the cell surface with the CD3 complex and ζ chain.
b. Rearrangement of β-, γ-, and δ-chain genes ceases as a result of the suppression of expression of RAG-1 and RAG-2.
c. The pre-T cell proliferates and produces a clone of cells all expressing an identical β chain.
d. Expression of CD34 and CD2 gives rise to double-positive thymocytes.
e. α-, γ-, and δ-chain loci rearrange simultaneously.

A

a. β binds to pTα and is expressed on the cell surface with the CD3 complex and ζ chain.
b. Rearrangement of β-, γ-, and δ-chain genes ceases as a result of the suppression of expression of RAG-1 and RAG-2.
c. The pre-T cell proliferates and produces a clone of cells all expressing an identical β chain.
e. α-, γ-, and δ-chain loci rearrange simultaneously.

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16
Q

Which of the following statements regarding positive selection is correct?

a. All subsets of developing T cells undergo positive selection before export to the peripheral circulation.
b. T-cell receptor editing is linked to the process of positive selection.
c. Positive selection results in the production of T cells bearing T-cell receptors that have the capacity to interact with all allotypes of MHC class I and class II molecules, and not just those of the individual.
d. Positive selection ensures that autoreactive T cells are rendered non-responsive.
e. If there is a genetic defect in AIRE, then T-cell development is arrested as positive selection commences.

A

T-cell receptor editing is linked to the process of positive selection.

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17
Q

Thymocytes that are not positively selected

a. undergo genetic reprogramming and differentiate into a different cell type
b. are exported to the periphery, where they are phagocytosed by macrophages
c. make up about 98% of developing thymocytes and die by apoptosis in the thymic cortex
d. are eliminated because of their reactivity with self antigens
e. try out different β chains to acquire reactivity with self-MHC molecules

A

make up about 98% of developing thymocytes and die by apoptosis in the thymic cortex

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18
Q

If the process of positive selection did not occur, then

a. a condition resembling immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) would develop
b. a condition resembling autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED) would develop
c. naive T cells would be unable to undergo differentiation in secondary lymphoid tissues
d. malignant transformation would be more likely because of the accumulation of multiple mutations
e. only a very small percentage of circulating T lymphocytes would be able to become activated

A

only a very small percentage of circulating T lymphocytes would be able to become activated

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19
Q

Immediately after positive selection

a. the thymocyte reaches maturity and is exported to the periphery
b. RAG proteins are degraded and are no longer synthesized
c. receptor editing commences to eliminate reactivity against self antigens
d. the developing thymocyte acquires a double-negative phenotype
e. expression of pTα is repressed

A

RAG proteins are degraded and are no longer synthesized

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20
Q

Allelic exclusion occurs for all of the following except

a. T-cell receptor α genes
b. T-cell receptor β genes
c. B-cell receptor heavy-chain genes
d. B-cell receptor κ-chain genes
e. B-cell receptor λ-chain genes

A

T-cell receptor α genes

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21
Q

Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED) is caused by a defect in

a. cathepsin L
b. a transcription factor that regulates tissue-specific gene expression in the thymus
c. the production of regulatory CD4 T cells
d. FoxP3
e. T-cell receptor gene rearrangement

A

a transcription factor that regulates tissue-specific gene expression in the thymus

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22
Q

Identify which of the following describes how antigen processing and presentation of self antigens by thymic epithelial cells differs from that of antigen-presenting cells in peripheral tissues. (Select all that apply.)

a. Thymic epithelium expresses MHC class I molecules but not MHC class II molecules.
b. Thymic epithelium uses cathepsin L for proteolytic degradation of self proteins.
c. Thymic epithelium expresses MHC class II molecules but not MHC class I molecules.
d. Thymic epithelium uses the transcription factor AIRE to activate thymic expression of tissue-specific genes.
e. Thymic epithelium expresses transcription repressor protein FoxP3.

A

b. Thymic epithelium uses cathepsin L for proteolytic degradation of self proteins.
d. Thymic epithelium uses the transcription factor AIRE to activate thymic expression of tissue-specific genes.

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23
Q

All of the following types of protein are processed and presented by macrophages in the thymus except _____ proteins.

a. tissue-specific
b. soluble proteins from extracellular fluids
c. ubiquitous proteins
d. proteins made by macrophages
e. proteins derived from other cells that macrophages phagocytose

A

tissue-specific

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24
Q

Healthy individuals have approximately ____ of CD4 T cells compared with CD8 T cells.

a. one quarter the number
b. half the number
c. equal numbers
d. twice the number
e. four times the number

A

twice the number

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25
Q

Double-negative thymocytes initiate rearrangement at the _____ locus (loci) before all other T-cell receptor genes.

a. γ and δ
b. β
c. α and β
d. α, γ, and δ
e. β, γ, and δ

A

β, γ, and δ

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26
Q

The function of negative selection of thymocytes in the thymus is to eliminate

a. single-positive thymocytes
b. double-positive thymocytes
c. alloreactive thymocytes
d. autoreactive thymocytes
e. apoptotic thymocytes

A

autoreactive thymocytes

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27
Q

Which of the following statements is correct?

a. In adults the mature T-cell repertoire is self-renewing and long-lived and does not require a thymus for the provision of new T cells.
b. T cells and B cells are both short-lived cells and require continual replenishment from primary lymphoid organs.
c. The human thymus is not fully functional until age 30, at which time it begins to shrink and atrophy.
d. In DiGeorge syndrome the bone marrow takes over the function of the thymus and produces mature peripheral T cells.
e. None of the above statements is correct.

A

In adults the mature T-cell repertoire is self-renewing and long-lived and does not require a thymus for the provision of new T cells.

28
Q

Individuals with a defective autoimmune regulator gene (AIRE) exhibit

a. DiGeorge syndrome
b. autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED)
c. severe combined immunodeficiency (SCID)
d. MHC class I deficiency
e. MHC class II deficiency

A

autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED)

29
Q

Giulia McGettigan was born full term with a malformed jaw, cleft palate, a ventricular septal defect, and hypocalcemia. Within 48 hours of birth she developed muscle tetany, convulsions, tachypnea, and a systolic murmur. A chest X-ray showed an enlarged heart and the absence of a thymic shadow. Blood tests showed severely depleted levels of CD4 and CD8 T cells; B-cell numbers were low but within normal range. Parathyroid hormone was undetectable. Fluorescence in situ hybridization of the buccal mucosa revealed a small deletion in the long arm of chromosome 22. Giulia failed to thrive and battled chronic diarrhea and opportunistic infections, including oral candidiasis and Pneumocystis jirovecii, the latter infection causing her death. Giulia most probably had which of the following immunodeficiency diseases?

a. AIDS
b. DiGeorge syndrome
c. bare lymphocyte syndrome
d. chronic granulomatous disease
e. hyper IgM syndrome

A

DiGeorge syndrome

30
Q

The human thymus begins to degenerate as early as one year after birth. This process is called ______ and is marked by the accumulation of ___ once occupied by thymocytes.

a. thymectomy; dendritic cells
b. involution; fat
c. differentiation; γ:δ T cells
d. negative selection; γ:δ T cells
e. involution; thymic stroma

A

involution; fat

31
Q

Which of the following is true of MHC class I and II molecules on the surface of thymic epithelial cells?

a. present only peptides derived from self-MHC molecules
b. present peptides derived from self proteins present in the thymus
c. present only peptides derived from self proteins transported to the thymus from the periphery
d. do not have any peptides bound to them

A

present peptides derived from self proteins present in the thymus

32
Q

Which of the following depicts the arrangement of the T-cell receptor β-chain locus? (n = multiple segments)

a. VβnJβnCβ1JβnCβ2
b. VβnDβ1Jβ1nCβ1Dβ2Jβ2nCβ2
c. VβnJβnCβ
d. VβnDβnJβnCβ

A

VβnDβ1Jβ1nCβ1Dβ2Jβ2nCβ2

33
Q

Which of the following describes the ligand for the receptor protein Notch1?

a. It is a transcription factor required for T-cell differentiation.
b. It is upregulated on double-negative thymocytes shortly after their commitment to the T-cell lineage.
c. It must be cleaved by a protease before it binds to Notch1.
d. It is a transmembrane protein on epithelial cells of the thymic stroma.

A

It is a transmembrane protein on epithelial cells of the thymic stroma.

34
Q

What would happen to a thymocyte that failed to cleave Notch1?

a. The thymocyte would rearrange the γ:δ-chain genes but not the α:β-chain genes.
b. The thymocyte would continue to block the T-cell lineage genes.
c. The thymocyte would start to express T-cell lineage genes.
d. The thymocyte would recruit co-activators to the T-cell lineage genes but would be unable to express those genes.

A

The thymocyte would continue to block the T-cell lineage genes.

35
Q

Which of the following is characteristic of individuals homozygous for defective alleles of the interleukin-7 (IL-7) receptor?

a. They have no T cells.
b. They can have either CD4 or CD8 T cells, but not both.
c. They lack a thymus.
d. They have elevated levels of CD34 on the surface of circulating T cells.

A

They have no T cells.

36
Q

Which of the following is true of the commitment to the CD4 or CD8 lineage by developing T cells?

a. It occurs because different types of signals are generated by the two co-receptors after they interact with MHC molecules.
b. It occurs when repression of one or the other co-receptor gene occurs randomly, giving rise to single-positive T cells.
c. T cells can change their expressed co-receptor during activation in the periphery.
d. It occurs because if both co-receptors are expressed in the late stages of T-cell development, the T cell is signaled to die by apoptosis.

A

It occurs because different types of signals are generated by the two co-receptors after they interact with MHC molecules.

37
Q

Which of the following activities is associated with pre-T cells? (Select all)

a. termination of CD4 and CD8 gene expression
b. allelic exclusion at the β-chain locus
c. expression of pTα
d. suppression of RAG1 and RAG2 gene expression
e. proliferation

A

b. allelic exclusion at the β-chain locus
d. suppression of RAG1 and RAG2 gene expression
e. proliferation

38
Q

In the pre-T-cell receptor, what is the function of pTα?

a. It forms a dimer, which binds to a single β chain.
b. It interacts with the variable and constant regions of the β chain.
c. It interacts with an exogenous ligand provided by the thymic stroma.
d. It transduces the signal from the pre-T-cell receptor through cytosolic ITAMs.

A

It interacts with the variable and constant regions of the β chain.

39
Q

What occurs during successive rearrangements at a T-cell receptor α-chain locus?

a. The developing T cell becomes single-positive.
b. The δ-chain locus on the same chromosome also rearranges.
c. The β-chain locus also rearranges.
d. The nonproductively rearranged V and J segments are deleted.

A

The nonproductively rearranged V and J segments are deleted.

40
Q

Which of the following is true of receptor editing of the T-cell receptor?

a. It occurs in secondary lymphoid organs.
b. It occurs at the β-chain locus.
c. It occurs to eradicate reactivity with self antigens.
d. It occurs to ensure reactivity with self-MHC molecules.

A

It occurs to ensure reactivity with self-MHC molecules.

41
Q

What is the function of Th-Pok?

a. transmits signals after the pre-T-cell receptor assembles
b. adds N nucleotides to the junctions between V, D, and J segments
c. replaces the surrogate light chain after the second checkpoint in T-cell development
d. acts as a transcription factor during the transition from double-positive thymocytes to single-positive CD4 T cells

A

acts as a transcription factor during the transition from double-positive thymocytes to single-positive CD4 T cells

42
Q

Mature T cells have T-cell receptors that can bind only to the particular self-MHC isoform that provided the signal for survival during T-cell development. What is this called?

a. monospecificity
b. negative selection
c. MHC restriction
d. positive selection

A

MHC restriction

43
Q

If an individual is homozygous for defective TAP-2, one of the proteins needed to transport peptides into the lumen of the endoplasmic reticulum, then what will be observed in the T-cell repertoire of this individual?

a. It will be completely absent.
b. It will lack cytotoxic T-cell function.
c. It will lack helper T-cell function.
d. It will contain a large proportion of autoreactive T cells.

A

It will lack cytotoxic T-cell function.

44
Q

The polypeptide pTα in developing T cells is analogous to what molecule in developing B cells?

a. κ and λ
b. the surrogate light chain
c. Igα:Igβ
d. Pax-5

A

b. the surrogate light chain

45
Q

Mature, naive, single-positive T cells leave the thymus via what route?

a. blood venules
b. high endothelial venules
c. direct migration through the thymic and heart tissue
d. the lymphatics

A

blood venules

46
Q

Which of the following correctly describes the functional form of the pre-T-cell receptor?

a. It is a superdimer composed of two heterodimers of pTα and a β chain.
b. It is a complex of γ and δ chains, CD3, and the ζ chain.
c. It is a trimer composed of pTα, a β chain, and Lck.
d. It is a heterodimer made of an α chain and a β chain.

A

It is a superdimer composed of two heterodimers of pTα and a β chain.

47
Q

Why is it necessary for mature T cells to be MHC restricted?

a. to allow transplantation of foreign tissue
b. to avoid interacting with self-MHC molecules
c. to recognize self-MHC molecules presenting pathogen-derived peptides
d. to avoid reacting with self antigen

A

to recognize self-MHC molecules presenting pathogen-derived peptides

48
Q

Double-negative thymocytes will not develop further unless they receive signals from which type of cell?

a. thymic antigen-presenting cells
b. thymic epithelial cells
c. thymic macrophages
d. thymic dendritic cells

A

thymic epithelial cells

49
Q

Unlike other CD4 T cells, what molecule do regulatory T cells (Treg) use to regulate subset-specific gene expression?

a. CD25
b. FoxP3
c. autoimmune regulator (AIRE)
d. Th-Pok

A

FoxP3

50
Q

Which of the following is true of the terminally differentiated type of effector cell that a CD4 T cell becomes after its activation by antigen?

a. It is influenced by the combination of cytokines present in the microenvironment in which it differentiates.
b. It is influenced by genomic programming that occurs during positive selection of that T cell.
c. It depends on whether it first encounters antigen in lymphoid organs or peripheral organs.
d. It is determined by its ability or inability to interact with Treg cells.

A

It is influenced by the combination of cytokines present in the microenvironment in which it differentiates.

51
Q

What occurs if an α:β T-cell receptor binds very strongly to self-peptide:self-MHC complexes in the thymic cortex?

a. α-chain rearrangement continues.
b. The T cell is rendered anergic.
c. Negative selection occurs.
d. The T cell leaves the thymus and dies shortly thereafter.

A

Negative selection occurs.

52
Q

Bare lymphocyte syndrome type II is caused by the inability to express MHC class II molecules. Which of the following is consistent with this abnormality?

a. The T-cell co-receptor CD4 is unable to signal through the protein kinase Lck, and so CD4 expression is halted in developing T cells.
b. CD8 on double-positive thymocytes fails to make contact with MHC class II molecules, causing cell death.
c. A defect in MHC class II molecules predisposes an individual to intracellular infections.
d. Th-Pok is functional and drives normal expression of genes needed for CD8 T-cell development.

A

The T-cell co-receptor CD4 is unable to signal through the protein kinase Lck, and so CD4 expression is halted in developing T cells.

53
Q

Which of the following is true of a nonproductive rearrangement at the T-cell receptor β-chain locus?

a. The cell cannot be rescued and dies through apoptosis.
b. It can be rescued by further rearrangement if the first rearrangement involved the Dβ1 and Jβ1 gene segments.
c. It never occurs, because the junctions between VD and DJ are always in frame.
d. It can be rescued by further rearrangement if the first rearrangement involved the Dβ2 and Jβ2 gene segments.

A

It can be rescued by further rearrangement if the first rearrangement involved the Dβ1 and Jβ1 gene segments.

54
Q

α-chain gene rearrangement can continue under what circumstances?

a. when a nonproductive α-gene rearrangement is made and when the T-cell receptor of double-positive thymocytes does not bind a self-MHC molecule
b. during the first checkpoint stage of early T-cell development and during the second checkpoint stage of early T-cell development
c. when all γ:δ-chain rearrangements have been exhausted
d. during positive and negative selection

A

when a nonproductive α-gene rearrangement is made and when the T-cell receptor of double-positive thymocytes does not bind a self-MHC molecule

55
Q

At what stage do the thymocytes become committed to the T-cell lineage?

a. the single-positive stage
b. upon entering the thymus
c. the double-positive stage
d. the double-negative stage

A

the double-negative stage

56
Q

How many attempts can a thymocyte make in attempt to make a productive β-chain gene?

a. one
b. four
c. two
d. eight

A

four

57
Q

What cell-surface molecules are being tested during positive selection resulting in the survival of the thymocyte?

a. pre-T-cell receptors
b. T-cell receptors that do not react with self antigens loaded in self-MHC molecules
c. T-cell receptors that can recognize self-MHC molecules in combination with self peptides
d. CD4 and CD8 co-receptors

A

T-cell receptors that can recognize self-MHC molecules in combination with self peptides

58
Q

Positive selection occurs exclusively in the cortex of the thymus, but where does negative selection occur?

a. exclusively in the medulla
b. exclusively in the cortex
c. in secondary lymphoid organs
d. in both the cortex and the medulla

A

in both the cortex and the medulla

59
Q

Which of the following is correct regarding a thymocyte committed to the γ:δ T-cell lineage?

a. It is committed to this lineage once it has productively rearranged a γ-chain locus.
b. It requires the expression of either CD4 or CD8.
c. It requires expression of the pre-T-cell receptor.
d. It can commit to this lineage after the double-negative or the double-positive stage of development.

A

It can commit to this lineage after the double-negative or the double-positive stage of development.

60
Q

What happens to thymocytes that are unable to produce functional T-cell receptors?

a. They become NK cells.
b. They die by apoptosis.
c. They are exported to the circulation, where they die shortly thereafter.
d. They rearrange their immunoglobulin loci.

A

They die by apoptosis.

61
Q

Why are T cells with an initially nonproductive α-chain gene rearrangement very likely to be rescued by a further productive rearrangement?

a. The α-chain locus contains large numbers of both V and J gene segments.
b. Each α-chain locus contains multiple sets of D and J gene segments associated with different C genes.
c. Different V gene segments can successively rearrange to the same J gene segment.
d. α-chain V gene segments can rearrange to δ-locus J gene segments as well as to α-locus J gene segments.

A

The α-chain locus contains large numbers of both V and J gene segments.

62
Q

If productive γ- and δ-chain gene rearrangements are made before a productive β-chain gene rearrangement occurs, then which of the following will occur?

a. The T cell receives the signal to undergo positive and negative selection.
b. The developing T cell is committed to the γ:δ T-cell lineage
c. The γ:δ heterodimer assembles as a pre-T-cell receptor.
d. β-chain gene rearrangement continues in an attempt to produce a functional β chain.

A

The developing T cell is committed to the γ:δ T-cell lineage

63
Q

At the completion of the cortex phase of T-cell development (early α:β T-cell development), what are expressed at the cell surface?

a. CD4, CD8, and a functional T-cell receptor
b. Kit and ZAP70
c. Notch1 and pre-T-cell receptor
d. Ikaros and GATA-3

A

CD4, CD8, and a functional T-cell receptor

64
Q

It has been estimated that around how many different self peptides can be presented by each MHC isoform?

a. 1000
b. 60,000
c. 10,000
d. 120,000

A

10,000

65
Q

Which of the following is a transcription factor that causes tissue-specific genes to be transcribed in medullary epithelial cells in the thymus?

a. autoimmune regulator (AIRE)
b. GATA-3
c. Th-Pok
d. Ikaros

A

autoimmune regulator (AIRE)

66
Q

What is a mechanism of the bias favoring commitment to the α:β T-cell lineage?

a. α-chain genes rearrange in advance of γ- or δ-chain genes during T-cell development.
b. β-chain genes rearrange in advance of γ- or δ-chain genes during T-cell development.
c. The γ:δ genes are not tested through the pre-T-cell receptor.
d. Only one productive rearrangement is required at both the double-negative and double-positive stages of T-cell development.

A

Only one productive rearrangement is required at both the double-negative and double-positive stages of T-cell development.

67
Q

When CD8 T cells become activated by antigen, they always differentiate into this type of cell, which can kill any host cell presenting their specific antigen.

a. γ:δ T cells
b. helper T cells
c. cytotoxic T cells
d. Treg cells

A

cytotoxic T cells