Cell Biology Questions and Answers – Immune Response – T-lymphocytes

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This set of Cell Biology online test focuses on “Immune Response – T-lymphocytes”.

1. T-cells are activated by _______________
a) autoantibodies
b) antibodies
c) fragments of antigens
d) intact antigens
View Answer

Answer: c
Explanation: Unlike B-cells, T-cells do not require intact antigens for activation rather small fragments of antigens. The antigen-presenting cells display fragments of antigens on their surfaces that can be recognized by the T-cell receptors.
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2. The dendritic cells were discovered by _______________
a) Ralph Steinman
b) Barry Marshall
c) David Baltimore
d) Peter Medawar
View Answer

Answer: a
Explanation: The vital antigen presenting cells (APCs) include dendritic cells and macrophages. Dendritic cells were discovered and characterized by Ralph Steinman of the Rockefeller University in 1970s.

3. Each T-cell has a single species of T-cell receptor.
a) True
b) False
View Answer

Answer: a
Explanation: Like B-cells, T-cells also undergo clonal selection. T-cells contain T-cell receptors that help them recognize and bind to certain infected cells or antigenic compounds. Each T-cell has a single species of T-cell receptors.

4. The activation of T-cell by the dendritic cells is associated with __________________
a) increase in magnesium ions
b) decrease in magnesium ions
c) increase in calcium ions
d) decrease in calcium ions
View Answer

Answer: c
Explanation: When the antigen-presenting cells – dendritic cells display fragments of antigens on their surface in the lymph nodes, the binding with a particular T-cell receptor occurs that leads to activation of the latter. The activation is associated with a transient increase in cytosolic calcium concentration.

5. Proliferation of T-cells in response to antigen presentation is accompanied by enlargement of __________________
a) lymph nodes
b) area of infection
c) size of antibody
d) size of B-cells
View Answer

Answer: a
Explanation: When a fragment of antigen binds to the T-cell receptor, it results in the proliferation of a particular clone of T-cells. A T-cell can proliferate 3 to 4 times per day, accompanied by enlargement of the lymph nodes.
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6. After the clearance of foreign antigen, the expanded T-cell population ________________
a) dies by apoptosis
b) increases in size
c) remains in the circulatory system
d) remains in lymph nodes
View Answer

Answer: a
Explanation: After the clearance of foreign antigen, the expanded T-cell population dies by apoptosis and a small population of memory T-cells remains for future contact with the same antigen.

7. T-cells secrete antibodies for eradicating the infected cells.
a) True
b) False
View Answer

Answer: b
Explanation: Unlike B-lymphocytes, the T-cells do not secrete antibodies for destroying the infected cells. The T-cells possess T-cell receptors on their surfaces, by which they can interact directly with the antigen-presenting cells.

8. Cytokines are ________________
a) antigens
b) proteins
c) polysaccharides
d) carbohydrates
View Answer

Answer: b
Explanation: Cytokines are small proteins that work at low concentrations; secreted by a wide variety of cells and include interferons (IFs), interleukins (ILs), and tumor necrosis factors (TNFs). In addition to cell-cell contact, the T-cells also mediate their interactions by cytokines.

9. Chemokines act as ___________________
a) buffers
b) receptors
c) chemoattractants
d) antibodies
View Answer

Answer: c
Explanation: Chemokines are a small family of cytokines that are powerful chemo-attractants that stimulate and regulate the migration of lymphocytes into the inflammation sites.
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10. Perforins and granzymes are secreted by ______________________
a) Cytotoxic T lymphocytes
b) Helper T lymphocytes
c) Regulatory T lymphocytes
d) B lymphocytes
View Answer

Answer: a
Explanation: Cytotoxic T lymphocytes patrol the body and screen cells for abnormalities. The CTLs secrete perforins in tightly enclosed space between cells that leads to the formation of transmembrane channels through which the granzymes enter the cells and direct them to apoptosis.

11. After entering the target cells, the granzymes activate the ______________________
a) antibodies
b) chemokines
c) perforins
d) caspases
View Answer

Answer: d
Explanation: After entering the target cells through the perforin transmembrane channels, the granzymes (proteolytic enzymes) activate caspases that direct the cells to undergo apotosis.

12. Cytotoxic T cells are _____________
a) CD2+
b) CD4+
c) CD6+
d) CD8+
View Answer

Answer: d
Explanation: The cytotoxic T-cells are CD8+ because they contain a surface protein CD8 (cluster designation 8). The CTLs screen the cells of the body for any abnormalities and then function to rectify them.

13. Helper T lymphocytes possess ____________ proteins on their surface.
a) CD2
b) CD3
c) CD4
d) CD5
View Answer

Answer: c
Explanation: The helper T cells have CD4 proteins on their surface instead of CD8 proteins as in case of cytotoxic T cells. Helper T cells play a role in orchestrating attack against a specific pathogen.
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14. Which of the following is the main target of HIV?
a) Helper T cells
b) Autoantibodies
c) Cytotoxic T cells
d) B lymphocytes
View Answer

Answer: a
Explanation: Helper T cells (TH) play an important role in the attack against specific antigens. The HIV attacks helper T cells which are necessary for the differentiation of B cells into antibody secreting plasma cells. When the count of TH cells in the body drops below 200 cells/μl the body becomes prone to infections.

15. Which of the following is an essential requirement for the differentiation of regulatory T cells?
a) FOXP1
b) FOXP2
c) FOXP3
d) FOXP4
View Answer

Answer: c
Explanation: Regulatory T lymphocytes are inhibitory cells that suppress proliferation of immune cells. They possess CD4+ and CD25+ markers on their surface. The proliferation of TReg cells require a transcription factor FOXP3.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn