Exam 3

Question 1

Which of the following statements about Notch 1 is incorrect?

Answer 1

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

Question 2

Immature B cells develop into B cells in the _______________.

Answer 2

Secondary Lymphoid organs

Question 3

Negative selection of developing B cells ensures that ___________.

Answer 3

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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

Thymocytes that are not positively selected _____________.

Answer 6

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

Question 7

In which of the following ways does the developmental pathway of alpha:beta T cells differ from that of B cells?

Answer 7

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 8

Which of the following statements is false of a T cell that expresses two alpha chains (and thus two different T-cell receptors) as a result of ineffective allelic exclusion of the alpha chain during rearrangement?

Answer 8

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

Question 9

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

Answer 9

positive selection

Question 10

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?

Answer 10

Bruton tyrosine kinase (Btk)

Question 11

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

Answer 11

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

Question 12

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

Answer 12

CD34

Question 13

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. common lymphoid progenitor: medulla
e. dendritic cells: cortico-medullary junction

Answer 13

double-negative CD3 thymocytes: cortico-medullary junction

Question 14

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

Answer 14

CD34 and CD4

Question 15

_____ 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.

Answer 15

CD2

Question 16

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).

Answer 16

Pax-5: FoxP3

Question 17

If the process of positive selection did not occur, then ______.

Answer 17

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

Question 18

In which location would plasma cells not be present?

Answer 18

afferent lymphatic vessels

Question 19

Receptor editing occurs _____.

Answer 19

in the bone marrow to establish self-tolerance of the B-cell repertoire

Question 20

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

Answer 20

apoptosis

Question 21

Megan 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. Megan failed to thrive and battled chronic diarrhea and opportunistic infections, including oral candidiasis and Pneumocystis jirovecii, the latter infection causing her death. Megan most probably had which of the following immunodeficiency diseases?

Answer 21

DiGeorge syndrome

Question 22

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

Answer 22

pTalpha:beta:CD3

Question 23

Immediately after positive selection __________.

Answer 23

RAG proteins are degraded and are no longer synthesized

Question 24

Which of the following would occur after the production of a functional mu 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 the allelic exclusion of a second mu chain.
e. All of the above would occur.

Answer 24

e. All of the above would occur.

Question 25

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

Answer 25

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

Question 26

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

Answer 26

twice the number

Question 27

Individuals with a defective autoimmune regulator gene (AIRE) exhibit ___.

Answer 27

persistent multiple organ autoimmune disease

Question 28

Which of the following statements is correct?

Answer 28

The kappa light-chain genes rearrange before the lambda light-chain genes.

Question 29

An important advantage of having two gene loci (kappa and lambda) for the light chain is ________.

Answer 29

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

Question 30

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

Answer 30

The mu chain is assembled with VpreB-lambda5.