This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Autoimmunity Factors and Mechanism”.
1. Autoantibodies block thyroid cell stimulation by responding to which of the following receptor?
a) Acetylcholine
b) Thyrotropin
c) Thyrocholine
d) Acetyltropin
View Answer
Explanation: Autoantibodies can induce damage to the body by binding to self-tissues, activating the complement cascade and inducing lysis or removal of cells by phagocytic immune cells. This occurs in certain forms of haemolytic anaemia when autoantibodies bind to red blood cell surface antigens inducing lysis of red blood cells. Autoantibodies can also interact with cell-surface receptors, altering their function. One of which is when autoantibodies respond to Thyrotropic receptor they block the cell stimulation of thyroid. Similarly, autoantibodies to the acetylcholine receptor block transmission at the neuromuscular junction resulting in myasthenia gravis.
2. Immune cells damage tissues indirectly by releasing cytotoxic cytokines, prostaglandins, reactive nitrogen or oxygen intermediates.
a) True
b) False
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Explanation: Damage induced by cells of the immune system play a major pathogenic role in many autoimmune diseases. The cells include phagocytic macrophages, neutrophils, self-reactive CD4+ T helper cells and self-reactive CD8+ cytolytic T cells, with smaller numbers of natural killer cells, mast cells and dendritic cells. Immune cells follow two pathways; direct and indirect. These immune cells damage tissues directly by killing cells.
3. Which of the following cells act as antigen-presenting cells to initiate autoimmune response?
a) Tissue macrophages
b) Cytokines
c) B cells
d) NK cells
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Explanation: Tissue macrophages as well as monocytes can act as antigen-presenting cells to initiate an autoimmune response once an immune response has been initiated. Macrophages act as killer cells through antibody-dependent cell-mediated cytotoxicity and by secreting cytokines, such as tumour necrosis factor (TNF) or interleukin (IL)-1, which act as protein signals between cells.
4. What is the major difference between IFN-gamma and IL-4?
a) IFN-gamma is immune-complex mediated while IL-4 is organ-specific
b) IFN-gamma is not involved in autoimmune disease while IL-4 is
c) IFN-gamma is a cytokine release by Th2 cells while IL-4 is release by Th1 cells
d) IFN-gamma is associated with organ-specific autoimmune diseases while IL-4 is associated with immune complex-mediated autoimmune diseases.
View Answer
Explanation: CD4+ T cells are classified as T helper 1 (Th1) or T helper 2 (Th2) cells depending on the release of cytokines. Th1 and Th2 cells release interferon-g (IFN-gamma) or IL-4, respectively. IFN-gamma is a proinflammatory cytokine associated with many organ-specific autoimmune diseases like type I diabetes and thyroiditis, while IL-4 activates B cells to produce antibodies and is associated with autoantibody/immune complex-mediated autoimmune diseases like lupus and arthritis.
5. The mechanism of peripheral T-cell tolerance does NOT include which of the following terms?
a) Clonal deletion
b) Clonal selection
c) Anergy
d) Ignorance
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Explanation: Peripheral Tolerance Mechanisms are associated with a number of activities carried out by mature B and T cells which include clonal deletion and its anergy along with ignorance. These activities are taken up which portray negative effects in our body that can further lead to improper regulation of the immunity and can result in inappropriate tolerance to antigens.
6. Which of the following cytokine inhibits Th1 immune response to reduce the activity of autoimmune disease?
a) TGF-beta
b) IFN-gamma
c) IFN-alpha
d) TGF-alpha
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Explanation: Suppressor or regulatory T-cell populations, including activated CD25+CD4+ regulatory T cells, exist in peripheral tissues and are important in controlling inflammation and autoimmune responses by killing autoreactive cells. These regulatory cells also secrete anti-inflammatory cytokines like IL-10 and transforming growth factor TGF-beta that inhibit Th1 immune responses which further helps in reducing inflammation and autoimmune disease.
7. Immune regulation is achieved by which of the following cells?
a) B cells
b) NK cells
c) Regulatory T cells
d) Cytotoxic T cells
View Answer
Explanation: Immune regulation is achieved by the action of Regulatory T cells (also denoted as Tregs). Treg are important in the maintenance of peripheral tolerance. Tregs are one of the most important cells in individuals. If any individual suffers from improper functioning of Tregs, he/she has a higher rate of lymphadenopathy. This error can also cause the immune system to respond with inflammation in multiple organs.
8. Which receptors are involved for innate immune cells to produce response to pathogens?
a) T cell receptors
b) Antigen Presenting Cell receptor
c) Pattern recognition receptor
d) B cell receptor
View Answer
Explanation: Activation of the innate immune system is essential for the development of a protective adaptive immune response against infection and for the development of autoimmune disease. Innate immune cells produce responses to particular classes of pathogens via pattern recognition receptors (PRR). One such type of PRR involved is Toll-like receptors (TLR). Interaction of pathogen-associated molecular patterns (PAMP) on microorganisms with PRR on antigen-presenting cells (APC) like macrophages and dendritic cells results in the upregulation of surface molecules essential for antigen presentation and the production of proinflammatory cytokines.
9. Which cytokines lead to induction of Th17 during infection?
a) TGF-beta
b) IFN-gamma
c) IFN-beta
d) TGF-alpha
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Explanation: TGF-beta in the presence of IL-6 (e.g., from activated macrophages during infection) and IL-23 can lead to induction of Th17. Th17 in turn produce cytokine – IL-17. Th17 are associated with antimicrobial immunity as well as autoimmune/inflammatory disorders. TGF-beta can therefore either regulate inflammation through Treg or promote inflammation through Th17. Hence, it is said that TGF-beta has a dual action in regulating autoimmune disease responses.
10. Activated T-cell expresses which cytokine for autocrine facilitation?
a) IL-4
b) IL-2
c) IFN-gamma
d) TGF-beta
View Answer
Explanation: Activated T cells express IL-2 and IL-2R cytokines for autocrine facilitation. This autocrine facilitation is associated with proliferation. T cells are usually activated by antigen presenting cells which cause them to further enhance the autocrine mechanism. This mechanism is mediated by clonal deletion which is one of the most important mechanism that takes part in peripheral T cell selection and tolerance.
Sanfoundry Global Education & Learning Series – Immunology.
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