Immunology T Cell Activation Quiz

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Questions and Answers

What is the primary function of dendritic cells in T cell activation?

  • To kill infected cells directly
  • To remain dormant until activated by T cells
  • To present protein antigens to T cells (correct)
  • To produce cytokines for T cell proliferation

Which signal is essential for the activation of T cells after antigen recognition?

  • Antigen extraction process
  • Costimulatory signal (correct)
  • Signal from cytokines only
  • MHC molecule activation

How do CD40L:CD40 interactions enhance T cell responses?

  • By enhancing the activation of antigen-presenting cells (correct)
  • By inducing apoptosis in T cells
  • By suppressing T cell proliferation
  • By promoting viral replication in T cells

What is the consequence of CTLA-4:B7 interactions during T cell activation?

<p>They inhibit the initial activation of T cells (B)</p> Signup and view all the answers

What role does PD-1 play in T cell regulation?

<p>Inhibits the activation of effector T cells (C)</p> Signup and view all the answers

Which of the following therapies targets the CD40L:CD40 pathway in clinical trials?

<p>Inhibitors for transplant rejection (B)</p> Signup and view all the answers

What is the mechanism by which therapeutic costimulatory blockade aims to regulate T cell activity?

<p>Modulating the balance between activating and inhibitory signals (D)</p> Signup and view all the answers

What is the primary role of IL-2 in T cell responses?

<p>Promotes survival and proliferation of T cells (B)</p> Signup and view all the answers

Which molecule is primarily expressed on T cells after activation?

<p>CD69 (D)</p> Signup and view all the answers

What is clonal expansion in the context of T cells?

<p>Increase in number of antigen-specific T cell clones (C)</p> Signup and view all the answers

Which factor is essential for the differentiation and function of regulatory T cells?

<p>IL-2 (D)</p> Signup and view all the answers

How does IL-2 influence the activity of other T cells?

<p>By promoting the production of IFN-γ and IL-4 (D)</p> Signup and view all the answers

Which of the following is NOT a change in surface molecule expression following T cell activation?

<p>Decrease in CD25 (IL-2Rα) (C)</p> Signup and view all the answers

Which surface molecule is typically associated with the costimulatory signal necessary for T cell activation?

<p>CD40L (CD154) (B)</p> Signup and view all the answers

What is the main source of IL-2 secretion in the early phase of T cell activation?

<p>CD4+ T cells (B)</p> Signup and view all the answers

What role do adhesion molecules play in T cell activation?

<p>They enhance T cell migration to tissues (A)</p> Signup and view all the answers

What characterizes the increased expression of anti-apoptotic proteins in memory T cells?

<p>It supports their prolonged survival and life span. (D)</p> Signup and view all the answers

How do memory T cells respond to antigen stimulation compared to naive T cells?

<p>More rapidly and effectively. (C)</p> Signup and view all the answers

What is the role of cytokines like IL-7 in memory T cell maintenance?

<p>They induce self-renewal in the absence of antigens. (A)</p> Signup and view all the answers

What triggers the contraction of the T cell response after antigen elimination?

<p>Inhibition of growth factor production. (A)</p> Signup and view all the answers

What is a key mechanism behind the decline of T cell responses?

<p>Increased activation of cellular stress sensors. (B)</p> Signup and view all the answers

Which statement regarding the characteristics of memory T cells is correct?

<p>They can migrate and respond to antigens in peripheral tissues. (B)</p> Signup and view all the answers

How do effector cells give rise to memory T cells?

<p>Along both linear and divergent differentiation pathways. (C)</p> Signup and view all the answers

Which of the following is NOT a factor contributing to the decline of T cell responses?

<p>Increased growth factor production. (D)</p> Signup and view all the answers

What is the significance of having a greater number of memory T cells compared to naive T cells?

<p>They ensure a more robust and quicker immune response to antigens. (A)</p> Signup and view all the answers

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Study Notes

Dendritic Cells and T Cell Activation

  • Dendritic cells are essential for presenting antigens to T cells. They capture antigens from the environment and migrate to lymph nodes where they interact with T cells.

  • Signal 1 - Antigen recognition by the T cell receptor (TCR) is essential for T cell activation. This involves the T cell recognizing a specific antigen presented by the dendritic cell.

  • Signal 2 - CD40L:CD40 interactions provide the second signal for T cell activation. CD40L on the T cell binds to CD40 on the dendritic cell, leading to the activation and maturation of the dendritic cell. This results in the increased expression of co-stimulatory molecules like B7.

  • CTLA-4:B7 interactions suppress T cell activation. CTLA-4, expressed on activated T cells, competes with CD28 for binding to B7. This interaction delivers an inhibitory signal, dampening T cell activation.

  • PD-1 plays a regulatory role by inhibiting T cell activation. It binds to its ligands, PD-L1 and PD-L2, which are expressed on various cells, including tumor cells. This interaction leads to the inhibition of T cell signaling and a reduction in T cell function.

T Cell Co-Stimulatory Pathways and Therapies

  • CD40L:CD40 pathway is targeted in clinical trials for its potential in cancer immunotherapy. Therapies blocking the CD40 pathway are being investigated for their ability to enhance antitumor immunity.

  • Therapeutic costimulatory blockade, such as CTLA-4 or PD-1 blockade, achieves therapeutic effects by regulating T cell activity. This approach involves blocking inhibitory pathways, allowing T cells to mount a robust response against tumors or pathogens.

IL2: Key Cytokine in T Cell Responses

  • IL-2, a key cytokine in T cell responses, is primarily produced by activated T cells. It promotes the growth and differentiation of T cells, enhancing their immune functions.

  • CD69 is predominantly expressed on activated T cells. It acts as a marker of activation and its expression is upregulated after T cell stimulation.

T Cell Clonal Expansion and Differentiation

  • Clonal expansion refers to the rapid proliferation of activated T cells, creating a large number of identical cells specific for the recognized antigen.

  • Foxp3 is crucial for the differentiation and function of regulatory T cells (Tregs). Tregs play a critical role in suppressing immune responses, maintaining tolerance, and preventing autoimmune reactions.

  • IL-2 influences the activity of other T cells by promoting the differentiation of effector T cells and supporting the survival and function of Tregs.

Changes in Surface Molecule Expression following T Cell Activation

  • Downregulation of CCR7 expression is a key change in surface molecule expression following T cell activation which aids in T cell migration to inflammatory sites.

  • CD28 is a surface molecule typically associated with the costimulatory signal necessary for T cell activation. It binds to B7 on antigen-presenting cells, providing the required second signal for T cell activation.

IL-2 Secretion and Adhesion Molecules in T Cell Activation

  • Activated T cells are the primary source of IL-2 secretion in the early phase of T cell activation. This IL-2 is crucial for their own proliferation and differentiation into effector cells.

  • Adhesion molecules, like LFA-1, facilitate the tight interaction between T cells and antigen-presenting cells. These interactions are essential for the delivery of activation signals and effective immune responses.

Memory T Cells: Properties and Differentiation

  • Memory T cells exhibit increased expression of anti-apoptotic proteins, which contributes to their prolonged survival and allows them to respond rapidly upon encountering the same antigen.

  • Memory T cells display more rapid and robust responses to antigen stimulation compared to naive T cells, enabling a quicker and more effective immune response upon re-exposure to the same pathogen.

  • Cytokines like IL-7 are crucial for the maintenance of memory T cells in the absence of antigen. They provide survival signals and maintain the pool of memory T cells, ensuring a rapid response upon subsequent encounters with the pathogen.

Contraction of T Cell Responses and Memory T Cell Generation

  • Elimination of the antigen triggers the contraction of the T cell response. This involves the removal of effector T cells, reducing the immune response to manageable levels.

  • A key mechanism behind the decline of T cell responses is the death of activated T cells due to the lack of antigenic stimulation and the withdrawal of survival signals. This ensures that immune responses are controlled and do not persist indefinitely.

  • Memory T cells are long-lived and exhibit enhanced survival, allowing them to persist even after the antigen is cleared. This provides rapid and effective immune responses upon re-exposure to the same pathogen.

  • Effector cells contribute to the generation of memory T cells. This is achieved through various mechanisms, including the expression of specific transcription factors and the retention of survival signals.

  • A greater number of memory T cells compared to naive T cells signifies a more robust and efficient immune response upon reencountering the same antigen. This enables a quicker and more effective defense against previously encountered pathogens, contributing to a more resilient immune system.

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