Exam 3: T cells

Question 1

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 1

pTalpha: beta:CD3

Question 2

Which of the following is mismatched?

Answer 2

double-negative CD3 thymocytes: cortico-medullary junction

Question 3

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

Answer 3

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 4

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?

Answer 4

CD34

Question 5

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 5

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

Question 6

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 6

Pax-5: FoxP3

Question 7

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

Answer 7

D-beta –> J-beta

Question 8

Which of the following statements about Notch 1 is incorrect?

Answer 8

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

Question 9

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

Answer 9

CD34 and CD4

Question 10

Allelic exclusion occurs for all of the following except _____________.

Answer 10

T-cell receptor alpha genes

Question 11

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

Answer 11

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

Question 12

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?

Answer 12

A pre-T-cell receptor is assembled as a super dimer

Question 13

_____ 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 13

CD2

Question 14

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

Answer 14

Pax-5

Question 15

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

Answer 15

Beta, gamma and delta

Question 16

Which of the following statements is correct?

Answer 16

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 17

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

Answer 17

Positive selection

Question 18

Thymocytes that are not positively selected _____________.

Answer 18

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

Question 19

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

Answer 19

Tissue-specific

Question 20

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.

Answer 20

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

Question 21

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.

Answer 21

Involution; fat

Question 22

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

Answer 22

Autoreactive thymocytes

Question 23

Immediately after positive selection __________.

Answer 23

RAG proteins are degraded and are no longer synthesized

Question 24

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 24

DiGeorge Syndrome

Question 25

Which of the following statements regarding positive selection is correct?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

Persistent multiple organ autoimmune disease

Question 29

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

Answer 29

Intracellular signaling by pre-T-cell receptors and positive selection of gamma: delta T-cells