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?

They inhibit the initial activation of T cells Signup and view all the answers

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

Inhibits the activation of effector T cells Signup and view all the answers

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

Inhibitors for transplant rejection Signup and view all the answers

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

Modulating the balance between activating and inhibitory signals Signup and view all the answers

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

Promotes survival and proliferation of T cells Signup and view all the answers

Which molecule is primarily expressed on T cells after activation?

CD69 Signup and view all the answers

What is clonal expansion in the context of T cells?

Increase in number of antigen-specific T cell clones Signup and view all the answers

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

IL-2 Signup and view all the answers

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

By promoting the production of IFN-γ and IL-4 Signup and view all the answers

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

Decrease in CD25 (IL-2Rα) Signup and view all the answers

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

CD40L (CD154) Signup and view all the answers

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

CD4+ T cells Signup and view all the answers

What role do adhesion molecules play in T cell activation?

They enhance T cell migration to tissues Signup and view all the answers

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

It supports their prolonged survival and life span. Signup and view all the answers

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

More rapidly and effectively. Signup and view all the answers

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

They induce self-renewal in the absence of antigens. Signup and view all the answers

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

Inhibition of growth factor production. Signup and view all the answers

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

Increased activation of cellular stress sensors. Signup and view all the answers

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

They can migrate and respond to antigens in peripheral tissues. Signup and view all the answers

How do effector cells give rise to memory T cells?

Along both linear and divergent differentiation pathways. Signup and view all the answers

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

Increased growth factor production. Signup and view all the answers

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

They ensure a more robust and quicker immune response to antigens. Signup and view all the answers

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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Description

Test your knowledge on the intricate processes of T cell activation and regulation. This quiz covers key interactions and therapies targeting T cells, as well as the roles of various proteins in the immune response. Perfect for students and professionals in immunology or related fields.