This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Lineage Commitment, Exit from Thymus and Final Maturation”.
1. Which organ is responsible for production of diverse population of T cells?
a) Thymus
b) Bone marrow
c) Liver
d) Spleen
View Answer
Explanation: Thymus is the home for T cells. This organ is known as a primary lymphoid organ which helps in the generation of self-tolerant T cells from the bone-marrow precursors. Once the T cells enter thymus for maturation, they undergo a number of steps specifically in the thymic cortex which further leads to their selection (either positive or negative).
2. Signals from TCR (T cell receptor) activate which of the following protein?
a) Protein tyrosine kinase
b) Cyclin dependent kinase
c) Collagen
d) Coronin and Elastin
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Explanation: Protein tyrosine kinase (also denoted as PTK) is one of the most important protein responsible for the activation of T cells. For carrying out the activation of T cells, this protein itself is in the inactive mode initially. In order to activate this protein, it requires the signals from T cell receptor (TCR), CD4 or CD8 T cells.
3. Lineage commitment is a process in which CD4–CD8– (double negative) thymocytes differentiate to CD4– and/or CD8– T cells.
a) True
b) False
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Explanation: Lineage commitment is a very important developmental process which is subjected to the differentiation of CD4+CD8+ (i.e., double-positive) thymocytes into CD4+ and/or CD8+ T cells. There are various steps which lead to this differentiation process. The thymocytes are committed to differentiate and they do not change their fate.
4. Which of the following stage is NOT involved in T lymphopoiesis?
a) Double-negative cell stage
b) Double-positive cell stage
c) Single-negative cell stage
d) Single-positive cell stage
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Explanation: T lymphopoiesis is divided into 3 important stages namely: double-negative, double-positive and single-positive cell stages. These 3 stages completely depend on the expression of CD4 and CD8 T cells. T lymphopoiesis involves a major role of lymphoid progenitor cells which travel from bone-marrow to the thymus for deciding the fate of CD4 and CD8 T cells.
5. The lineage commitment of immature to mature T cells is mediated by which of the following receptor?
a) BCR
b) TCR
c) APR
d) APC and TCR
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Explanation: Lineage commitment is a very important process for maintenance of the immune system as it involves the differentiation and maturation of immature CD4+CD8+ T cells to mature CD4+ or CD8+ T cells. This is mediated by T cell receptors which are expressed clonally and generated somatically.
6. The thymus provides an inductive environment for T lineage commitment at which of the following loci?
a) Gamma-delta and alpha-beta TCR
b) Alpha-delta and gamma-delta TCR
c) Alpha-gamma TCR
d) Alpha-beta TCR
View Answer
Explanation: Thymus is known as a site for the development and maturation of T lymphocytes. This is a primary lymphoid organ that provides a sufficient environment for lineage commitment of T lymphocytes. This process is mediated by T cell receptors (TCRs) at two major loci which are gamma-delta TCR locus and alpha-beta TCR locus.
7. Which of the following researcher studied the use of Rag2p-GFP in mice?
a) John Stewart
b) Fink
c) Edward Jenner
d) Pasteur
View Answer
Explanation: In the study of lineage commitment during the exit of T cells from the thymus for final maturation, Fink and few of his colleagues found that mice showed the presence of green fluorescent protein (GFP). This GFP consisted of high levels of double-positive thymocytes which strongly expressed Rag2 gene. They further studied the association of the protein and the gene it expressed i.e., Rag2-GFP.
8. In what phase do the thymocytes enter the thymus?
a) Double-positive markers
b) Double-negative markers
c) Single-positive markers
d) In their original form
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Explanation: Thymocytes enter the thymus as double negative markers. They travel from bone marrow to the thymus for their further development. When maturation and developmental processes of thymocytes take place, they further transform to double positive markers. They express CD4 and CD8 to form double positive markers.
9. What changes take place in PTK (protein tyrosine kinase) on binding of CD4 to MHC?
a) It activates CD45
b) It activates ZAP70 to become an active PTK
c) It activates the phosphatase to become an active PTK
d) It binds to CD45
View Answer
Explanation: Activated protein tyrosine kinase helps in activating the T cells by receiving the signals from TCR (T cell receptor), CD4 or CD8. Specifically, CD4 and CD8 are associated with the cytoplasmic tyrosine kinase enzyme. This enzyme is also known as lymphocyte kinase (Lck). When CD4 binds to MHC, it allows Lck to phosphorylate and activate ZAP70 to become an active protein tyrosine kinase.
10. T cells proliferate and differentiate into which of the following cells on receiving primary response?
a) Effector T cells only
b) Memory T cells only
c) Effector and Memory T cells
d) Helper, Effector and Memory T cells
View Answer
Explanation: Before proliferation and differentiation takes place, T cells lack the experience of functionality. At this stage these T cells are designated as naïve T cells. They need some type of response to activate. As a result, they receive a primary response due to which they proliferate and differentiate into Effector and Memory T cells.
Sanfoundry Global Education & Learning Series – Immunology.
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