60 Questions
What is the primary advantage of utilising highly specific antigen receptors in adaptive immunity?
Recognition of pathogens lacking stereotypical PAMPs
What is the outcome of the resolution phase of an immune response?
Contraction of the immune response
What is the primary role of T cells in immune responses?
Orchestration of immune responses
What is the outcome of T cell activation?
T cell differentiation
What is the primary mechanism of adaptive immunity?
Antigen-specific recognition
What is the primary function of CD4+ and CD8+ T cells?
Helper function and cytotoxicity
What is the primary function of cytotoxic T cells?
To kill infected cells
What is the main difference between effector and memory T cells?
Effector T cells are activated upon antigen recognition, while memory T cells are not
What is the role of antigen-presenting cells in T cell activation?
To present antigens to helper T cells, which then activate cytotoxic T cells
What is the significance of MHC class I in T cell activation?
It is involved in the recognition of antigens by cytotoxic T cells
What is the primary function of helper T cells?
To assist other white blood cells in the immune response
What is the difference between naïve and effector T cells?
Naïve T cells are not activated, while effector T cells are activated
What is the primary function of γδ T cells in the immune system?
To directly kill infected cells
What determines the differentiation of T cells into specific subsets?
The cytokine environment created by the APC and other cells
What is the term used to describe the process of T cell differentiation into specific subsets based on the cytokine environment?
T cell polarisation
What is the function of Th2 cells?
To combat extracellular parasites and helminths
What is the primary function of Tregs?
To regulate and inhibit immune responses
What is the role of the third signal in T cell activation?
To direct T cell differentiation into specific subsets
What is the primary function of T-Bet in Th1 and Th2 cross-regulation?
To repress the expression of GATA-3 and the TH2 effector cytokines
Which of the following cytokines is involved in the differentiation of Th1 cells?
IL-12
What is the primary function of GATA-3 in Th1 and Th2 cross-regulation?
To up-regulate the synthesis of IL-4 and IL-5
Which of the following cell subsets is involved in B cell activation and Ab production?
TfH
What is the primary function of IL-4 in Th1 and Th2 cross-regulation?
To promote the expression of GATA-3
Which of the following cytokines is involved in the differentiation of Th17 cells?
IL-6
What is the primary requirement for CD8+ T cell activation, in addition to the two signals provided by the APC?
More co-stimulation than Th cells, usually provided by effector CD4+ Th cells
How do CD4+ Th cells help activate CD8+ T cells?
By producing IL-2 and expressing CD40L
What is the consequence of the requirement for CD8+ T cells to be activated by related antigens presented by BOTH MHC I and MHC II on the same APC?
Most viruses are unable to activate CD8+ T cells
What is the role of CD40L in CD8+ T cell activation?
It binds to CD40 on the APC, enhancing CD80/CD86 expression
Why are CD4+ Th cells necessary for CD8+ T cell activation?
They provide co-stimulation for CD8+ T cell activation
What is the consequence of CD4+ Th cells recognizing related antigen on the APC?
CD4+ Th cells are activated and produce IL-2 and CD40L
T cell activation requires only one signal from the antigen-presenting cell.
False
Adaptive immunity can only be achieved through natural exposure to pathogens.
False
CD4+ T cells are involved in the humoral immune response.
False
The primary role of T cells is to recognize and eliminate infected cells and present antigens to B cells.
False
Effector-memory T cells are like naïve T cells upon activation.
False
The resolution phase of an immune response results in the expansion of immune cells.
False
T cells can recognize pathogens with stereotypical PAMPs.
False
CD4+ T cells are involved in the destruction of intracellular pathogens.
False
CD8+ T cells can recognize antigens presented by antigen-presenting cells through MHC class II.
False
Antigen recognition is the only step required for T cell activation.
False
Naïve T cells are a type of memory T cell.
False
T cell activation only occurs in peripheral infected organs.
False
Co-stimulatory molecules are necessary for the activation of CD8+ T cells but not CD4+ T cells.
False
CD8+ T cells can be activated by a single signal provided by the APC.
False
The protein Lck is involved in the activation of T cells through its interaction with ITAM.
True
CD40L binds to CD40L on the APC, which stimulates it to make more costimulatory CD80/CD86.
False
The production of cytokine, mainly IL-2, is induced by the first signal of T cell activation.
False
CD8+ T cells can be activated by unrelated antigens presented by the APC.
False
CD4+ Th cells help activate CD8+ T cells by providing cytokines and CD28.
False
CD80 and CD86 are co-stimulatory molecules found in mice.
False
T cell activation results in the suppression of transcription factors and gene expression.
False
CD80/CD86 is the murine equivalent of human B7.1/B7.2.
False
The clonal expansion of T cells is a result of antigen recognition by the TCR/MHC interaction.
False
Viruses are naturally trophic for dendritic cells, allowing for efficient activation of CD8+ T cells.
False
Almost all effector T cells die once the antigen is eliminated.
False
Cross presentation of exogenous antigens to MHC-I is important for CD4+ T cell activation
False
CD80/86-CD28 is enough for CD8+ T cell activation
False
MHC class I molecules only present peptides from endogenous antigens
False
The third signal in T cell activation is antigen recognition
False
Th1 cells produce TNFα/IFNγ and mediate humoral immune responses
False
Study Notes
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T cell development and activation involves five key learning outcomes: the role of T cells in immune responses, the maturation and selection process for CD4+ and CD8+ T cells, stages and development of T cell-mediated immunity (CMI), the 2 steps to T cell activation, and the 3rd signal and T cell differentiation.
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Adaptive immunity is an immune response that becomes more powerful following repeated encounters with the same antigen, utilizing highly specific antigen receptors that allow for recognition of pathogens lacking stereotypical PAMPs, highly specific responses for a given pathogen, and immunological memory.
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The advantages of adaptive immunity include highly diverse populations of cells, pathogen-specific cells expanding and improving in the repertoire, and resolution (contraction) and memory.
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Specific immunity can be achieved through natural exposure (e.g., chickenpox) or artificially by vaccination (e.g., MMR/COVID).
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T cells are long-lived and can be reactivated, making them essential for immune responses.
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T cell terminology includes naïve, effector, and memory T cells, with naïve T cells being the precursors of effector T cells.
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Effector T cells are further divided into effector-memory and central memory T cells, with effector-memory T cells having a more rapid response to antigen.
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The magnitude of T cell response involves the activation of naïve T cells, the expansion of effector T cells, and the contraction and homeostasis of memory T cells.
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T cell activation requires two signals: antigen recognition (MHC/antigen-TCR) and costimulation (CD80/86-CD28), with the 3rd signal (cytokine environment) dictating the type of T effector cell.
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CD4+ T cells (Th cells) recognize antigen presented by MHC class II and assist other white blood cells, while CD8+ T cells (Tc cells) recognize antigen presented by MHC class I and kill infected cells.
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The 3rd signal (cytokine environment) directs T cell differentiation into different subsets, including Th1, Th2, Th17, Tregs, and Tfh cells.
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Cytokines produced by antigen-presenting cells (APCs) and other cells create a cytokine environment that influences T cell differentiation.
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Differentiation of Th cells is induced by different cytokines, producing different types of effector CD4+ T cells, each with distinct functions.
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Th1 cells are involved in anti-inflammatory responses, peripheral tolerance, and bacterial infections, while Th2 cells are involved in pro-inflammatory responses, B cell activation, and helminth infections.
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Th17 cells are involved in pro-inflammatory responses, bacterial infections, and autoimmune diseases.
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Tregs are involved in anti-inflammatory responses, peripheral tolerance, and autoimmune diseases.
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TfH cells are involved in B cell activation and antibody production.
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Cross-presentation of exogenous antigens to MHC-I is important for CD8+ T cell (CTL) activation, which requires Th help and CD40-CD40L interaction.
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The dynamics of T cell response involve antigen recognition, activation, antigen elimination, contraction/homeostasis, and memory.
Test your knowledge on the role of T cells in immune responses, their maturation and selection process, and the stages of T cell mediated immunity. Learn about the two steps to T cell activation and the third signal in T cell differentiation.
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