This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “T-Cell Memory”.
1. From what source does the formation of Memory T cells occur?
a) From naïve T cells
b) From T cells that migrate to thymus
c) From differentiated T cells
d) From cytotoxic T cells
View Answer
Explanation: Naïve cells are those cells that have not responded to pathogen anytime earlier. When they first encounter a pathogen, they rapidly attack and fight against it with the help of cytokine proteins. These defending cells are called effector T cells. During the killing action, most of the effector T cells die but few of them survive. These survived cells are then called the memory T cells as they will fight rapidly if they again come in contact with the same pathogen (or they will attack rapidly if reinfection occurs).
2. Which epigenetic alteration associated with gene repression determines function and status among memory T cells?
a) Histone modification
b) DNA methylation
c) Non-coding RNA changes
d) DNA reprogramming
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Explanation: Scientists like Youngblood and his colleagues found out that DNA modification is one of the epigenetic alterations which determines the function and status among memory T cells as well as effector T cells. DNA methylation helps memory T cells to live longer and remain active for fighting against pathogens. However, memory T cells need very limited methylation of naïve associated genes to maintain this long living stage after they arise from effector T cells. Further researches suggest that there has been an identification of DNA methyltransferase called Dnmt3a which regulates the T cell stages through DNA methylation.
3. Which cell surface markers are associated with Tissue resident memory T cells (TRM)?
a) CD4 and CD8
b) CD16 and CD103
c) CD69 and CD103
d) CD45 and CD62
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Explanation: Tissue resident memory T cells are present in tissues of skin, gastrointestinal tract, lungs, etc. CD69 and CD103 are two of the most important cell surface markers associated with Tissue resident memory T cells. CD69 acts as a co-stimulatory molecule in order to activate all the T cells. It is also responsible for T cell differentiation and acts as a mediator for migrating to different tissues of the body. On the other hand, CD103 helps in maintaining immune homeostasis and T-cell mediated regulation.
4. Memory T cells do NOT migrate to which of the following peripheral sites?
a) Intestine
b) Skin
c) Lung airways
d) Spleen
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Explanation: Although memory T cells are found in all parts of the body, they have specific mechanisms for migrating towards the peripheral sites. When there is any infection in lungs, intestine or skin, there is a production of large number of memory T cells as compared to the production of memory T cells at other peripheral sites. The skin, intestine and lung airways when infected, consist of replicating pathogens for which large amount of memory T cell production is required. As a result, they migrate in bulk to these peripheral sites.
5. The combined expression of which types of molecules can control the trafficking of memory T cells?
a) Adhesion molecules and cytokine receptors
b) Cytokine receptors and NK cells
c) Adhesion molecules and interleukins
d) Interleukins and NK cells
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Explanation: The expression of different combinations of adhesion molecules and chemokine receptors can mediate the control of memory T cell trafficking. It has been demonstrated that memory T cells from the skin and gut have unique patterns of expression of these molecules. Along with this, glycosylation of these surface molecules can alter their interaction with specific ligands.
6. Which two ligands are expressed by migration of memory T cells to the skin?
a) P-selectin and D-selectin ligands
b) P-selectin and E-selectin ligands
c) E-selectin and D-selectin ligands
d) D-selectin and F-selectin ligands
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Explanation: The memory T cells which are programmed to migrate to skin express two ligands namely P-selectin and E-selectin. They undergo specific protein modifications that allow them to bind to E-selectin expressed by vascular endothelial cells. These modified ligands also help in expressing chemokine receptor 4 (CCR4) which interact with the dermal-associated chemokines.
7. Which of the following pulmonary surfactant contributes to maintain the cellular stress of memory T cells in the lungs?
a) Surfactant protein A1
b) Sodium stearate
c) Benzalkaonium chloride
d) Perfluorooctanesulfonate
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Explanation: Memory T cells in lung airways exist near the atmospheric oxygen concentrations and are mediated by hydrophilic surfactant proteins that help in maintaining low surface tension in the airway. The main pulmonary surfactant is surfactant protein A1 as well as SP-D which have various immunoregulatory functions that maintain the cellular stress for T cells in the lung airways.
8. Memory T cells migrating to mucosa decrease expression of which receptors?
a) IL-7 and IL-6
b) IL-6 and IL-15
c) IL-7 and IL-15
d) IL-10 and IL-2
View Answer
Explanation: The expression of IL-7 and IL-15 is decreased when memory T cells migrate to mucosa. This might inhibit the homeostatic turnover of these memory T cells. This can result in apoptosis. However, lymphoid and peripheral memory T cells have a great ability to resist these apoptotic processes.
9. After infection caused in particular part of the body, memory T cells get divided in which of the following subsets?
a) CD62L and CCR4
b) CD62L and CCR7
c) CD62L and CCR10
d) CD62L and CCR6
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Explanation: Memory T cells established after infection can be divided into two subsets based on expression of the lymphoid homing receptors – CD62L and CCR7. These subsets are distributed among the central memory and effector memory T cells. In central memory T cells, the receptor exhibit CD62L+ and CCR7+ and they get localized in lymphoid tissues whereas in effector memory T cells they exhibit CD62L– and CCR7– and clump in peripheral tissues.
10. Which of the following memory T cells have a greater chance of being affected by apoptotic process?
a) Central memory T cells
b) Effector memory T cells
c) Splenic memory T cells
d) Memory T cells that present peripheral sites
View Answer
Explanation: Splenic memory T cells migrating towards peripheral environment have greater chances to be affected by apoptosis. Although they have the ability to protect the host cells during infections, there are some rare scenarios where splenic memory T cells are inhibited from performing their action against the infected cells. In such cases, the ability of splenic memory T cells to survive in the periphery is regulated after their entry to peripheral sites.
Sanfoundry Global Education & Learning Series – Immunology.
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