This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Early Thymocyte Development”.
1. Immature double negative thymocytes are characterised by which of the following cell surface antigen?
a) CD4
b) CD44
c) CD17
d) CD8
View Answer
Explanation: Thymocytes comprise of the early T cell progenitor that are present in the thymus and are a part of minor population of lymphoid cells. They lack presence of expression of CD4 and CD8 coreceptor molecules. Major population of thymocytes is immature double negative and are characterised by the expression of CD44 and CD117 cell surface antigens.
2. Which of the following proteins are important for development of lymphocytes?
a) E2A-encoded proteins
b) E3A-encoded proteins
c) Insulin and Myosin
d) Tubulin and E2A-encoded proteins
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Explanation: E2A-encoded proteins play a major role in developmental process of lymphocytes. They are help in differentiation of various cell types. E2A gene encodes two major transcription factors namely E47 and E12 which bind to DNA in order to carry out the developmental process of lymphocytes. These transcription factors are known as basic helix-loop-helix factors.
3. Notch-signalling plays a major role early thymocyte development. True or False?
a) True
b) False
View Answer
Explanation: Notch-signalling has many roles in the developmental processes of thymocytes. It usually decides the fate of the T cell traversing from a multipotent to haematopoietic progenitor cells. This signalling process helps in providing differentiation, survival, metabolic signals as well as proliferation of the thymocytes.
4. What does TSPs stand for?
a) Thymic seedling progenitor cells
b) Thymic seeding progenitor cells
c) Thymus-seeded progenitor cells
d) Thymus-segregation progenitor cells
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Explanation: TSPs stands for Thymic Seeding Progenitor cells. These cells, along with another set of cells named Early Thymic Progenitor cells (ETPs), originate from the bone marrow. They enter the thymus at a particular junction which is known as Cortico-medullary junction for further development of thymocytes. These cells lack the expression of CD4 and CD8, hence are termed as double-negative cells.
5. Which of the following are known as Double-negative-2 cells?
a) CD4 and CD8
b) CD12+ and CD4+
c) CD44+ and CD8+
d) CD44+ and CD25+
View Answer
Explanation: CD44+ and CD25+ are the double negative 2 cells and are also designated as DN2 cells. These cells control the T lineage specification and migrate to the cortex in order to begin gene segment rearrangements. Once the lineage specification is successful, DN2 cells undergo a transitional state and develop into DN3 cells (CD44– and CD25+).
6. Which of the following transcription factor is NOT activated by notch-signalling?
a) Gata3
b) Tcf7
c) Tcf4
d) Hes1
View Answer
Explanation: Notch-signalling is a crucial step required for early thymocyte development. The recent study says that this signalling process activates various transcriptional factors like Gata3, Tcf7 and Hes1 to promote T cell specification and mediate the fates of T cells. Out of these three factors, Gata3 has a major role in mediating various stage of T cell development.
7. Which of the following comprises of the DN4 cell population?
a) CD44–CD25–
b) CD44–CD25+
c) CD44+CD25–
d) CD44+CD25+
View Answer
Explanation: DN stands for double negative cell population that are at play during early thymocyte development. These cells develop step by step from DN2 to DN3 to DN4. DN4 comprises of CD44–CD25– cells and they regulate the expression of CD4 and CD8. These cells further lead to yield double-positive (DP) cells.
8. During positive selection, useful thymocytes undergo developmental process to develop into which of the following cells?
a) CD4+ helper or CD8+ cytotoxic
b) Immature CD4+ or CD8+
c) Cytotoxic T cells only
d) B cells and CD4+ helper T cells
View Answer
Explanation: Positive selection of thymocytes is one of the most crucial steps for their development. The thymocytes that get positively selected are those cells who bear useful and responsive T cell receptors. They further differentiate to form CD4+ helper T cells or CD8+ cytotoxic lineage cells along with mature CD4+ or CD8+ cells.
9. What type of receptor is Notch?
a) Heteropentameric receptor
b) Heterohexameric receptor
c) Heterotrimeric receptor
d) Heterodimeric receptor
View Answer
Explanation: Notch is one of the most important receptors which carries out the notch signalling process necessary for thymocyte development and its commitments. The research has studied mammal models in which it is found that Notch is a heterodimeric receptor. It binds to two mammal families-the Delta and Serrate family.
10. What do the rearranged DP (double-positive) cells undergo in the cortex?
a) Negative selection
b) Negative and positive selection
c) Development
d) Differentiation
View Answer
Explanation: On production of the double-positive cells, there are quite a few changes in the overall development of thymocytes. These cells produce alpha-beta T cell receptors in order to undergo negative as well as positive selection in the cortex. They also separately undergo only negative selection in the medulla which further give rise to MHC-1 or MHC-2 population.
Sanfoundry Global Education & Learning Series – Immunology.
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