This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Maintenance of Self Tolerance and Apoptosis”.
1. Which of the following is NOT an injurious stimulus to cause apoptosis?
a) Hypoxia
b) Complement attack
c) Ligation
d) Overproduction of antibodies
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Explanation: Apoptosis is the term which means programmed cell death. It has a major role in immune system as it eliminates the unwanted cells by causing their death. It is characterised by biochemical changes and may result from insufficient survival signals. It can be caused by various injurious stimuli such as hypoxia, complement attack, ligation of Fas (CD95) cell surface death receptor along with cytokine activity of tumour-necrosis factor-alpha, etc.
2. Self-tolerance requires to deactivation of autoreactive T cells.
a) True
b) False
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Explanation: It is true that self-tolerance requires removal or deactivation of autoreactive T cells that have a specificity to central as well as peripheral antigens. The T cells that react to self-antigens are usually present in the thymus. In the developing thymus, this engagement of T cells induces apoptosis and deletion of the T cells that can prove harmful for the development of thymus as well as for the entire working of immunity.
3. What is the full form of AICD?
a) Activation induced cell destruction
b) Adaptation induced cell death
c) Activation induced cell death
d) Adaptation infected cell death
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Explanation: AICD stands for activation induced cell death. It is a process which completely depends on the ligation of the cell surface Fas death receptor. It has a major role in the regulation of T cell populations in which activation of T cell receptor results in apoptosis. AICD in peripheral T cells is caused by induction of expression of the Fas ligand which is known as the death ligand.
4. Which patients exhibit autoimmune lymphoproliferative syndrome?
a) The patients that show mutations in the genes encoding Fas ligand
b) The patients that encode Fas ligand
c) The patients that undergo immunodeficiencies to affect Fas ligand
d) The patients that show improper gene functioning
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Explanation: The recent research says that there have been a small number of patients that have shown mutations in the genes encoding either Fas or Fas ligand. These patients are said to have auto-immune lymphoproliferative syndrome (also designated as ALPS) which further causes antibodies to direct towards the blood components such as erythrocytes and platelets.
5. What does the surface of apoptotic cells express?
a) Autoantibodies
b) Autoantigens
c) T cells
d) Fas ligand
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Explanation: The surfaces of apoptotic cells express potential autoantigens. These autoantigens may have a possibility to cause autoimmune diseases. They are also recognised by our immune system in the patients that are suffering from autoimmune diseases. However, most of the people do not get affected by autoimmune disorders and in such cases the apoptotic cells also fall short and weak to induce any type of autoimmune disorder in the individual.
6. Which of the following Treg cell in NOT involved in controlling peripheral immune response?
a) CD4+
b) CD25+
c) Foxp3+
d) Foxp4+
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Explanation: Tregs are very sensitive to apoptosis. They control and maintain the peripheral immune responses. If at all these Tregs fail to control the exact balance of the immune responses, they might become weak and undergo apoptosis. As a result, 3 main Treg cells help in complete maintenance of peripheral immune response are CD25+, CD4+ and Foxp3+ in order to avoid the path of apoptosis.
7. Which cells do NOT show stimulation mediated by apoptotic cells?
a) CD4+
b) CD6+
c) CD28+
d) CD16+
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Explanation: Apoptotic cells are nothing but the cells that undergo death or are also termed as dying cells. These cells fail to stimulate presentation mainly to CD4+ T cells. However, these cells follow an exogenous pathway in order to escalate the presentation of CD8+ T cells. This is completely possible due to the antigens associated with the apoptotic cells.
8. Which interleukin (or cytokine) is noted to be produced by apoptotic cells?
a) IL-7
b) IL-10
c) IL-2
d) IL-6
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Explanation: IL-10 is predicted to be produced by apoptotic cells. This prediction was first framed by few scientists like Gao, Tomimori and Chen et al. They also have noticed that apoptotic cells produce transforming growth factor-beta. However, a recent study has shown that its not necessary for all apoptotic cells to undergo production of these cytokines and growth factors. This study predicts that certain macrophages or phagocytic cells might produce them in response to the apoptosis.
9. Which of the following DNA-binding protein is released from necrotic cell?
a) HMGB2
b) G1
c) HMGB1
d) Histone
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Explanation: HMGB1 is a DNA-binding protein which is released from necrotic cell. This is a nuclear protein and is released in a non-programmed way. One of the main differences between apoptotic and necrotic cell is that necrotic cell has a high affinity to dangerous signals as compared to the former, i.e., apoptotic cells. The study of release of HMGB1 from necrotic cell was framed by scientists like Choi and Obeid in the year 2006 and 2007 respectively.
10. Which of the following enzyme is activated by apoptotic cell?
a) Caspase protease
b) Nuclease
c) Peroxidase
d) Telomerase
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Explanation: Involvement of Caspase Protease is very important in apoptosis in response to immune system. This enzyme is activated in apoptotic cell and is mediated by signalling pathway. Caspase protease is mainly concerned to play role in programmed cell death and many cellular events associated with apoptosis like fragmentation of DNA and cells into apoptotic bodies.
Sanfoundry Global Education & Learning Series – Immunology.
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