This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “T-Cell Differentiation”.
1. In which part of the human body does the maturation, proliferation and differentiation of T cells occur?
a) Thymus
b) Bone Marrow
c) Hematopoietic cells
d) Lymph node
View Answer
Explanation: Immature T cells arise in bone marrow however they mature and differentiate in the Thymus. They proliferate and go through various developmental pathways in order to generate functional subpopulation of mature T cells. Differentiation of T cells is carried out after their activation in thymus itself. During maturation, T cells get sorted into helper, cytotoxic and memory T cells. Differentiation leads to generation of subsets of T cells.
2. Which is the right order of the steps involved in differentiation of T cells?
i) Activated T cell generation into blast cell
ii) Proliferation of blast cell
iii) Differentiation of daughter cells
iv) Differentiation into subsets of T cells
a) iii)—ii)—i)—iv)
b) iv)—ii)—iii)—i)
c) i)—ii)—iii)—iv)
d) ii)—i)—iv)—iii)
View Answer
Explanation: T cell differentiation starts after activation of T cell. The activated T cell then turns into a large blast cell mediated by developmental processes. This blast cell then proliferates by clonal expansion. (Clonal expansion is the process in which daughter cells arise from parent cell). This proliferation results in formation of daughter cells and they differentiate into effector (cytotoxic), memory and helper T cells. The helper T cells further differentiate into subsets of T cells.
3. Which of the following are major drivers of T cell differentiation?
a) CD4+ T cells
b) Cytokines
c) T cell receptors
d) Antigen presenting cells
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Explanation: Cytokines play a very important role in T cell differentiation. Cytokines are cell signalling molecules that help the cell in cell-cell communication in immune responses. They stimulate the movement of cells towards site of infection or inflammation. They generate signalling receptor complexes and decide the fate of T cells after differentiation.
4. Which HSC (Hematopoietic stem cell) marker identifies human progenitor cells for development of T cells in human?
a) CD4+
b) CD38+
c) CD34+
d) CD8+
View Answer
Explanation: CD34+ and CD7+ are present in human thymus and they represent early thymocyte progenitors. However, CD34+ alone identifies the progenitor cells and directs them for further development into T cells. Once developmental process is complete, CD34+ directs these T cells to enter Lymph nodes. On the other hand, CD34+ is used clinically to identify hematopoietic stem cells for transplantation of these cells.
5. Which cytokine is primarily involved in T cell development?
a) IL-6
b) IL-1
c) IL-2
d) IL-5
View Answer
Explanation: IL-6 as well as IL-21 are majorly involved in development of T cells. IL-6 helps in enhancing the proliferation of T cells. It is also considered to be the co-stimulatory molecule as it helps in stimulation of differentiation of T cells. During activation of T cells, in some cases, the T cells undergo cell death. In such a case, IL-6 protects the cells from activation induced cell death (AICD).
6. Which transcription factor is required for Th1 (T helper type 1) differentiation?
a) STAT1
b) STAT4
c) STAT6
d) STAT2
View Answer
Explanation: The differentiation of Th1 is driven by IL-12 and it requires STAT4 as a transcription factor. T helper type-1 (Th1) cells transcribe the T-bet transcription factor and produce interferon gamma (IFNg), interleukin-2 (IL-2), and lymphotoxin genes. These cells direct immunity against intracellular bacteria and viruses. On the other hand, the differentiation of Th2 is driven by IL-4 and requires STAT6 as a transcription factor.
7. Low T cell count is due to which of the following reason?
a) Infectious mononucleosis
b) Acute lymphocytic leukaemia
c) Multiple myeloma
d) Waldenstrom’s macroglobulinemia
View Answer
Explanation: Low T cell count is common than high T cell count. However, Waldenstrom’s macroglobulinemia is still a rare symptom. It can cause increased levels of IgM antibodies in human body than required. Other most common symptoms seen in individuals are aging, viral infections like influenza, immunodeficiency disorders, HIV/AIDS, etc. Low T cell count usually indicates problems with immune system or lymph nodes.
8. CD8 T cells proliferate and initially differentiate into which type of lymphocyte?
a) Helper T lymphocyte (Th)
b) Cytotoxic T lymphocyte (CTL)
c) Memory T lymphocyte
d) Regulatory T lymphocyte
View Answer
Explanation: CD8 T cells proliferate and progressively differentiate into Cytotoxic T lymphocytes (CTLs). The proliferation of CD8 T cells require repeated encounters with antigens. This antigenic stimulus triggers the developmental process and hence it causes differentiation of CD8 T cells. As and when the entire developmental process is completed by committing CD8 T cells to differentiate, they activate Tumour-necrosis factor and kill infected cells.
9. Which transcription factor is the master regulator of CD8 differentiation?
a) STAT1
b) Runx3
c) GATA3
d) Runx1
View Answer
Explanation: Runx family members are DNA-binding transcription factors that regulate the expression of genes involved in cellular differentiation and cell cycle progression. They also play an important role in haematopoiesis and help in development of T cell. They act as a transcription factor for differentiation of CD8 T cells. If there is a deficiency of Runx3, it can cause major reduction of CD8 T cells. This can lead to autoimmune diseases in young children.
10. The process which causes thymocytes to develop into mature T cells is called as Thymopoiesis.
a) True
b) False
View Answer
Explanation: Thymopoeisis is defined as the process which helps in development of thymocytes into mature T cells. Thymocyte is the cell which is present in the Thymus and it carries out various functions in response to our immune system. Thymopoeisis takes place either by positive or negative selection. Positive selection takes place to help T cells bind to MHC complex in order to attack and kill foreign cells while negative selection directs the T cells in such a way so that they recognize their own cells and do not attack them.
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