Immunology Questions and Answers – Establishment and Maintenance of Tolerance

This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Establishment and Maintenance of Tolerance”.

1. Who pioneered clonal selection theory?
a) Edward Jenner
b) MacFarlane Burnet
c) Joseph Brown
d) MacConkey 
View Answer

Answer: b
Explanation: MacFarlane Burnet was the first one to give the theory of Clonal Selection. This theory stated that our immunological memory has the ability to respond to the foreign allergen or antigen when we have a second encounter with it. In other words, it means that our immune system has a memory stored with the history of the past antigens encountered in out body due to which on second encounter, this memory is utilised by our immune system to fight against them. 

2. Which mechanism of tolerance is involved in Central Tolerance?
a) Clonal ignorance
b) Clonal selection
c) Clonal deletion
d) Suppression of lymphocytes
View Answer

Answer: c
Explanation: Central tolerance involved inactivation of cells required for the initiation of an immune response. The major site of this type of tolerance are the generative lymphoid organs and they affect the limb of the immune response which is concerned with sensitisation and cell proliferation. The main mechanism involved is Clonal deletion which results in apoptotic cell death. Negative selection is generally preferred by Central Tolerance as its main function is to eliminate the self-reactive lymphocytes.

3. How are thymocytes with low affinity selected?
a) Positively
b) Negatively
c) Positively as well as negatively
d) Thymocytes with low affinity are eliminated
View Answer

Answer: a
Explanation: Central tolerance is achieved by the deletion of autoreactive thymocytes through negative selection. However, thymocytes with a low or intermediate affinity are positively selected, whereas thymocytes with a higher affinity are negatively selected and undergo clonal deletion. High‐affinity interactions can also signal thymocytes to differentiate into the forkhead box protein 3 (Foxp3)‐expressing Treg lineage, resulting in a Treg repertoire skewed toward self‐recognition. 

4. Who discovered Regulatory T cells (Tregs)?
a) S. Sakaguchi
b) Edward Jenner 
c) Louis Pasteur
d) Peter Medawar
View Answer

Answer: a
Explanation: Regulatory T cells (denoted by Tregs) were first discovered by S. Sakaguchi a decade ago. Tregs play an important role in controlling the immune reactivity against self-antigens. They are also involved in responding to chronic inflammation and they show a great ability in maintenance of tolerating mechanisms of the immunity when an individual encounters tumour.   

5. What is the state of unresponsiveness to antigen termed as?
a) Clonal selection
b) Ignorance
c) Anergy
d) Immune Regulation
View Answer

Answer: c
Explanation: Anergy is defined as a state where the immune system fails to respond to the particular antigen. In other words, it is the state of unresponsiveness to antigen. This term has a slight inclination towards the peripheral T cell tolerance and its selection processes. The T cells that showcase anergy are known as anergic T cells and they fail to respond to the similar stimuli portrayed by antigens. 

6. B-cell peripheral Tolerance mechanism occurs in which of the following parts of the body?
a) Lymph nodes
b) Secondary Lymphoid Tissue
c) Bone marrow
d) Liver
View Answer

Answer: b
Explanation: Secondary Lymphoid Organs are mainly prone to undergo B cell peripheral tolerance mechanisms. This is because there are variations in the T cell tolerance and these are nearly equal to imperfect. Many of the autoimmune diseases consist of B cells that are usually T cell dependent due to which they completely rely on similar autoreactive T cells.  

7. Tregs develop in bone marrow.
a) True
b) False
View Answer

Answer: b
Explanation: Tregs (Regulatory T cells) develop in thymus and are present in healthy individuals from birth. These Tregs are referred to as natural Tregs. CD4+ CD25+ FoxP3+ Tregs are derived from mature naïve CD4+CD25T cells. There is no specific surface marker associated with Tregs as a result, FoxP3 has been identified as a key regulatory gene for the development and function of Tregs. 

8. Costimulation tolerance potentiates which of the following cytokine by following the costimulatory pathway?
a) IL-2
b) IL-3
c) IL-4
d) IL-16
View Answer

Answer: a
Explanation: Costimulation pathway influences the outcome of T‐cell stimulation and play a central role in immune tolerance. The definition of costimulatory pathways is not limited to the surface receptors that potentiate TCR signals, such as CD28 or inducible costimulator (ICOS), but also it also includes immunoregulatory receptors such as cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4) and programed death‐1 (PD‐1), and most importantly the soluble factor IL‐2, which is intimately linked and has overlapping functions with some costimulatory receptors.

9. How does deletion of B cells take place after primary activation?
a) By somatic mutation
b) By dual elimination
c) By irregularities
d) By attack of the antigens
View Answer

Answer: a
Explanation: Mature B cells, unlike mature T cells, can undergo somatic mutation of their BCR (B cell receptor) after antigenic stimulation. This property allows affinity maturation of the response in germinal centres to produce higher affinity antibodies, and it also creates a new risk of autoantibody development. There is one mechanism to solve this problem is analogous to the costimulator strategy in T cells. 

10. Which type of cells (B and T cells respectively) participate in Peripheral Tolerance Mechanism?
a) Immature B cells and mature T cells
b) Mature B cells and immature thymocytes
c) Immature B cells and immature thymocytes 
d) Mature B and Mature T cells
View Answer

Answer: d
Explanation: Peripheral tolerance mechanism involves inhibition of expression of immune response. The main site of this tolerance are the peripheral lymphoid tissues. Two of the most important cells to be associated with this mechanism are mature B and mature T cells. Peripheral Tolerance Mechanism supports various activities carried out by these two types of cells like cell death, clonal deletion and anergy along with clonal ignorance and few of the effector functions. 

Sanfoundry Global Education & Learning Series – Immunology.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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