Questions and Answers
What is the primary function of helper T cells in the immune response?
Which cells have T cell receptors that can only recognize peptide antigens?
Where does the process of VDJ rearrangement take place for T cells?
What is the role of MHC class I molecules in the immune system?
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What must happen for a naive T cell to become an effector T cell?
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Which type of antigen presenting cell is primarily associated with MHC class II molecules?
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Which of the following is true regarding T cell receptors?
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How do cytokines influence T cell differentiation?
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What is the primary role of the variable domains in the alpha and beta chains of the T cell receptor?
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How does the T cell receptor differ from the B cell receptor regarding antigen binding sites?
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What triggers T cell activation after the T cell receptor binds to antigen?
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What is the consequence of a T cell encountering its antigen without co-stimulation?
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What do ITAM regions in the CD3 complex facilitate?
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Which component of the IL-2 receptor is essential for high-affinity binding of IL-2?
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Which chain in the CD3 complex has the highest number of ITAM regions?
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What is the primary function of CD28 on a T cell?
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Which transcription factors are activated due to signaling through the T cell receptor?
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What does ZAP-70 do once activated?
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Which cytokine is produced by the activated T cell and is crucial for T cell proliferation?
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What best describes the role of the immune synapse?
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In which type of T cell is CD4 primarily expressed?
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What is the term for T cell division triggered by IL-2?
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Study Notes
Immune Response Fundamentals
- Adaptive immune response is highly specific, differentiating between friendly bacteria and deadly pathogens by recognizing antigens.
- Key cells involved are lymphocytes: B cells and T cells.
T Cell Development and Types
- T cells mature in the thymus through a process called VDJ rearrangement, producing diverse T cell receptors (TCRs).
- Two main T cell types:
- Helper T cells (CD4+): Support other immune cells.
- Cytotoxic T cells (CD8+): Kill infected or cancerous cells.
T Cell Activation
- Naive T cells are primed and activated to become effector T cells upon stimulation.
- Activation requires two signals:
- Signal 1: TCR binds to peptide antigens presented on MHC molecules.
- Signal 2: Co-stimulation occurs when CD28 on T cells binds to B7 on antigen presenting cells (APCs).
Major Histocompatibility Complex (MHC)
- MHC molecules display antigens to T cells.
- MHC Class I: Presents to CD8+ T cells, found on all nucleated cells.
- MHC Class II: Presents to CD4+ T cells, located on APCs (macrophages, dendritic cells).
T Cell Receptor (TCR) Structure
- TCR consists of an alpha chain and beta chain with variable and constant domains.
- Antigen binding occurs at the variable domains.
- T cell receptors are surface-bound; they cannot be secreted, unlike B cell receptors.
Immune Synapse and Signaling
- The immune synapse forms between the T cell receptor, MHC-antigen, CD4/CD8, and B7-CD28 interaction.
- Activation signals are transmitted to the nucleus using CD3 complex chains.
ITAMs and Signal Transduction
- CD3 complex contains immune receptor tyrosine-based activation motifs (ITAMs).
- ITAM phosphorylation is essential for T cell activation; requires both bound CD4/CD8 and the MHC antigen.
- Kinase Lck phosphorylates ITAMs, enabling ZAP-70 kinase to bind and propagate the signal.
Transcription Factor Activation
- ZAP-70 phosphorylates LAT and SLP-76, triggering pathways that activate transcription factors NFkappaB and NFAT.
- These factors promote cytokine expression (e.g., IL-2) and cell survival markers (e.g., Bcl-2).
IL-2 and Clonal Expansion
- Activated T helper cells produce IL-2, upregulating their high-affinity IL-2 receptor (alpha, beta, gamma components).
- Autocrine stimulation occurs as T cells bind IL-2 they produce, leading to rapid cell division (clonal expansion).
Recap of T Cell Types and Activation Signals
- Two T cell types are CD4+ (helper) and CD8+ (cytotoxic).
- Activation requires:
- Signal 1: Antigen-MHC interaction.
- Signal 2: CD28-B7 co-stimulation.
- Successful activation leads to IL-2 receptor upregulation, promoting proliferation and differentiation of T cells.
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Description
Dive into the specifics of the adaptive immune response in this quiz. Learn about B and T cells, their receptors, and the process of VDJ rearrangement in T cells. Test your knowledge on how the immune system differentiates between friendly and harmful invaders.
