Chapter 7 quiz

Question 1

In which of the following ways does the developmental pathway of alpha:beta 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 and T cells do not rearrange their antigen-receptor genes in the bone marrow.
e. T cells rearrange their antigen-receptor genes in the bone marrow.

Answer 1

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

Question 2

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

Answer 2

d. CD34

Question 3

Which of the following processes is not dependent on an interaction involving MHC class I or class II molecules?

a. positive selection of alpha:beta T cells
b. intracellular signaling by pre-T-cell receptors and positive selection of gamma:delta T cells
c. negative selection of alpha:beta T cells
d. peripheral activation of mature naive T cells
e. None of the above.

Answer 3

b. intracellular signaling by pre-T-cell receptors and positive selection of gamma:delta T cells

Question 4

If a double-negative thymocyte has just completed a productive beta-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 gamma- and delta-chain genes commences.
c. Expression levels of RAG-1 and RAG-2 are elevated.
d. The linked delta-chain genes are eliminated.
e. This cell will inevitably differentiate into a committed gamma:delta T cell.

Answer 4

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

Question 5

All of the following cell-surface glycoproteins are expressed by double-negative thymocytes undergoing maturation in the thymus except _____.

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

Answer 5

d. CD34 and CD4

Question 6

_____ 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. CD

Answer 6

d. CD2

Question 7

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.

Answer 7

a. double-negative CD3– thymocytes: cortico-medullary junction

Question 8

Which of the following statements about Notch 1 is incorrect?

a. Notch 1 is expressed on thymic epithelial cells, and in the absence of Notch 1 expression, T cells can complete their differentiation.
b. Notch 1 is to T-cell development as Pax-5 is to B-cell development.
c. Notch 1 contains two distinct domains, one of which is proteolytically cleaved and becomes a transcription factor in the nucleus.
d. 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.

Answer 8

a. Notch 1 is expressed on thymic epithelial cells, and in the absence of Notch 1 expression, T cells can complete their differentiation.

Question 9

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

a. V-alpha –> D-alpha
b. D-alpha –> J-alpha
c. V-beta –> D-beta
d. D-beta –> J-beta
e. V-alpha –> J-alpha

Answer 9

d. D-beta –> J-beta

Question 10

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. gamma:beta:CD3
b. beta:CD3
c. alpha:beta:CD3
d. beta:CD44
e. pTalpha:beta:CD3

Answer 10

e. pTalpha:beta:CD3

Question 11

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

Answer 11

c. Pax-5

Question 12

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. VpreBlambda5: pTalpha
b. Igalpha/Igbeta:CD3
c. Pax-5: FoxP3
d. multiple kappa and lambda light-chain gene rearrangements: multiple alpha-chain gene rearrangements.
e. Pax-5: CD3

Answer 12

c. Pax-5: FoxP3

Question 13

_______ of thymocytes is necessary to produce a T-cell repertoire capable of interacting with self-MHC molecules.

a. positive selection
b. negative selection
c. apoptosis
d. receptor editing
e. isotype switching

Answer 13

a. positive selection

Question 14

Which of the following statements is false 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?

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 gamma:delta T-cell receptor.

Answer 14

e. Subsequent gene rearrangements may give rise to a gamma:delta T-cell receptor.

Question 15

Once a thymocyte has productively rearranged a beta-chain gene, which of these events cannot occur subsequently?

a. beta binds to pTalpha and is expressed on the cell surface with the CD3 complex and zeta chain.
b. Rearrangement of beta-, gamma- and delta-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 beta chain.
d. Expression of CD34 and CD2 gives rise to double-positive thymocytes.
e. Alpha-, gamma-, delta-chain loci rearrange simultaneously.

Answer 15

d. Expression of CD34 and CD2 gives rise to double-positive thymocytes.

Question 16

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.

Answer 16

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

Question 17

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
d. are eliminated because of their reactivity with self antigens
e. try out different β chains to acquire reactivity with self-MHC molecules
cortex

Answer 17

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

Question 18

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.

Answer 18

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

Question 19

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 pTalpha is repressed

Answer 19

b. RAG proteins are degraded and are no longer synthesized

Question 20

Allelic exclusion occurs for all of the following except _____________.

a. T-cell receptor alpha genes
b. T-cell receptor beta genes
c. B-cell receptor heavy-chain genes
d. B-cell receptor kappa-chain genes
e. B-cell receptor lambda-chain genes

Answer 20

a. T-cell receptor alpha genes

Question 21

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

Answer 21

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

Question 22

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.

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 expresses transcription repressor protein FoxP3.
e. Thymic epithelium expresses MHC class II molecules but not MHC class I molecules.

Answer 22

b. Thymic epithelium uses cathepsin L for proteolytic degradation of self proteins.

Question 23

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

Answer 23

a. tissue-specific

Question 24

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

Answer 24

d. twice the number

Question 25

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

a. gamma and delta
b. beta
c. alpha and beta
d. alpha, gamma, and delta
e. beta, gamma, and delta

Answer 25

e. beta, gamma, and delta

Question 26

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

Answer 26

d. autoreactive thymocytes

Question 27

27. 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

Answer 27

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.

Question 28

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

Answer 28

b. autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED)

Question 29

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

Answer 29

b. DiGeorge syndrome

Question 30

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; gamma:delta T cells
d. negative selection; gamma:delta T cells
e. involution; thymic stroma

Answer 30

b. involution; fat