T and B Cell Signaling Pathways

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Questions and Answers

Which type of feedback loop decreases the activity of upstream components?

Cyclic feedback loop

Negative feedback loop (correct)

Positive feedback loop

Linear feedback loop

What is cross-talk between signaling pathways primarily used for?

To isolate cells from external signals

To enhance the fidelity of a single pathway

To allow integration and coordination of multiple signals (correct)

To initiate new signaling cascades without interaction

What is the primary role of feedback regulation in signaling pathways?

To inhibit competing signaling pathways

To modulate the signaling pathway by its own products (correct)

To amplify the signaling response indefinitely

To enhance the energy efficiency of signaling processes

Which of the following is NOT a common post-translational modification?

Nucleotide exchange Signup and view all the answers

What is the function of GTPase-activating proteins (GAPs)?

To enhance hydrolysis of GTP to GDP Signup and view all the answers

How do GTPases like Ras function within signaling pathways?

They act as molecular switches cycling between GTP and GDP states Signup and view all the answers

What effect does positive feedback in a signaling pathway have?

It enhances and sustains the pathway's activity Signup and view all the answers

Which modification is typically associated with altering the function of signaling proteins?

Post-translational modification Signup and view all the answers

What is the primary function of T cell receptor (TCR) signaling?

Trigger a signaling cascade leading to T cell activation Signup and view all the answers

Which component is NOT part of the B cell receptor (BCR) signaling pathway?

CD3 complex Signup and view all the answers

What role does NF-κB play in the immune system?

Induces expression of genes involved in immune responses Signup and view all the answers

Which of the following correctly describes the JAK-STAT signaling pathway?

It transmits signals from cytokine receptors to regulate gene expression Signup and view all the answers

What happens upon activation of NF-κB?

It translocates to the nucleus to regulate gene expression Signup and view all the answers

Which component is essential for T cell activation via TCR signaling?

Zap-70 Signup and view all the answers

What is the ultimate outcome of successful BCR signaling?

Production of antibodies by plasma cells Signup and view all the answers

Which proteins are negative regulators within the JAK-STAT signaling pathway?

SOCS proteins Signup and view all the answers

What is the primary function of T cells after activation?

Proliferation, migration, cytokine production, or apoptosis Signup and view all the answers

What are the two signals required for T cell activation?

Antigen recognition and costimulatory signal Signup and view all the answers

Which components of the T cell antigen receptor are responsible for genetic rearrangement?

Clonotypic α and β chains Signup and view all the answers

What could be a consequence of an inappropriate activation of T cells?

Autoimmune diseases Signup and view all the answers

Which coreceptors interact with antigen presenting cells to provide the costimulatory signal?

CD28 and CD4 Signup and view all the answers

What is the role of the CD3 complex in T cell activation?

Connecting the TCR to signaling pathways Signup and view all the answers

What may occur if T cells fail to activate in response to pathogens?

Infection and potential death Signup and view all the answers

What specialized role do CD4+ T cells have in the immune response?

They primarily activate B cells to produce antibodies. Signup and view all the answers

What type of molecules do naive T cells recognize with their T cell receptors (TCRs)?

Peptide antigens bound to MHC molecules Signup and view all the answers

Which receptor is commonly associated with co-stimulation during T cell activation?

CD28 receptor Signup and view all the answers

What is the role of immune checkpoints like CTLA-4 and PD-1?

They maintain homeostasis and prevent autoimmunity Signup and view all the answers

What must occur after the initial T cell activation for the T cell response to be effectively controlled?

Expression of costimulatory and coinhibitory molecules Signup and view all the answers

What is the primary function of naive T cells in lymphoid tissues?

To become effector T cells against tumors Signup and view all the answers

What initial signal is required for T cell activation aside from TCR recognition?

Recruitment of co-stimulatory molecules Signup and view all the answers

Which of the following is NOT a co-stimulator mentioned for T cell activation?

CTLA-4 Signup and view all the answers

Which sequence correctly represents T cell activation's first steps?

TCR recognition, co-stimulator recruitment Signup and view all the answers

What is the main role of Syk kinase in the signaling pathway?

Being recruited and activated by phosphorylated ITAMs Signup and view all the answers

Which adaptor proteins are involved in the formation of the signalosome around Syk?

BLNK, BTK, PLC-γ2 Signup and view all the answers

What is the result of PLC-γ2 activation within the signalosome?

Breakdown of PIP2 into IP3 and DAG Signup and view all the answers

Which molecule leads to intracellular calcium release in the calcium mobilization step?

IP3 Signup and view all the answers

How is the Ras/MAPK pathway activated?

When Ras activates the MAPK cascade Signup and view all the answers

What is the final outcome of B cell activation within this signaling pathway?

Secretion of antibodies and formation of memory B cells Signup and view all the answers

What role does DAG play in the activation of the NF-κB pathway?

It activates PKC Signup and view all the answers

What does the degradation of IκB lead to in the NF-κB pathway?

Translocation of NF-κB to the nucleus Signup and view all the answers

Study Notes

T Cell Activation Signaling Pathway

T cell activation involves a complex signaling cascade triggered by antigen recognition and costimulatory signals.
The primary signal involves the binding of foreign antigens to the T cell antigen receptor (TCR) in the context of MHC molecules on APCs.
TCR consists of α and β chains for antigen specificity and invariant γ, δ, ε, and ζ chains for signaling.
The second signal, or costimulatory signal, arises from the interaction of coreceptors like CD28 or CD4 with their ligands on APCs.
Key signaling molecules involved: TCR, CD3 complex, ZAP-70, Lck, LAT, SLP-76, PLC-γ, MAPK/ERK, NFAT, NF-κB, AP-1
T cell activation leads to proliferation, cytokine production, and differentiation into various T cell subsets.

B Cell Receptor (BCR) Signaling Pathway

BCR signaling is essential for B cell activation, proliferation, antibody production, and class switching.
B cells recognize antigens through their BCRs.
Key signaling molecules involved: BCR, Igα/Igβ complex, Lyn, Fyn, Syk, BLNK, PLC-γ2, BTK, PI3K, Akt, NF-κB, MAPK
BCR signaling promotes B cell survival, activation, and differentiation.

NF-κB Signaling Pathway

NF-κB is a transcription factor that plays a crucial role in regulating immune responses, inflammation, and cell survival.
NF-κB is activated by various receptors, including TCRs, BCRs, and cytokine receptors.
Key signaling molecules involved: IκB kinase (IKK) complex, IκB, NF-κB dimers (p65/RelA, p50), TNF receptor, IL-1 receptor, TLRs.
Upon activation, NF-κB translocates to the nucleus and induces the expression of genes involved in immune responses, inflammation, and cell survival.

JAK-STAT Signaling Pathway

The JAK-STAT pathway transmits signals from cytokine receptors to the nucleus.
Key signaling molecules involved: cytokine receptors, JAKs (JAK1, JAK2, JAK3, Tyk2), STAT proteins (STAT1, STAT3, STAT5), SOCS proteins (negative regulators).
Upon cytokine binding, JAKs are activated leading to phosphorylation and activation of STAT proteins which dimerize and translocate to the nucleus.

Immune Checkpoint Regulation Pathways

Immune checkpoints (e.g., CTLA-4, PD-1) are crucial for maintaining homeostasis and preventing autoimmunity.
They can also contribute to tumor immune evasion.
They act as regulators of T cell responses by inhibiting their activation and function.

B Cell Signaling Pathway: Step-by-Step Diagram Activity

Antigen binding to BCR initiates the signaling cascade.
BCR cross-linking activates Src-family kinases (Lyn, Fyn, Blk).
These kinases phosphorylate ITAMs on Igα/Igβ, recruiting and activating Syk kinase.
The formation of a signalosome complex involving BLNK, BTK, and PLC-γ2 occurs.
PLC-γ2 activation leads to the breakdown of PIP2 into IP3 and DAG, initiating calcium mobilization.
DAG activates PKC, leading to the degradation of IκB and release of NF-κB, which translocates to the nucleus.
The Ras/MAPK pathway is also activated, leading to ERK activation.
The result is B cell activation, proliferation, and differentiation into plasma cells and memory B cells.

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Description

This quiz focuses on the signaling pathways involved in T cell and B cell activation. It covers the roles of various receptors, key signaling molecules, and the processes that lead to immune responses. Test your knowledge on the complexities of these essential immune functions.