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Questions and Answers
What type of cytokines are produced by activated Th2 cells that affect antibody production?
What is the role of the Th1 cytokine IFN-γ in relation to B cells?
How are conjugate vaccines designed to enhance immunity to polysaccharides?
Granulomas are characterized by the presence of which type of cells?
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What is the outcome when polysaccharides are presented in a T cell-independent manner?
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What determines the lineage commitment of CD4 T cells in response to a pathogen?
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Which cytokine is produced by APCs to induce a Th1 response?
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What is the primary role of IFN-γ in the Th1 immune response?
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Which statement regarding the Th1 and Th2 immune responses is accurate?
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What is the consequence of macrophages infected with mycobacteria in the context of the immune response?
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How does the JAK:STAT pathway relate to CD4 T cell differentiation?
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What is the role of antigen-presenting cells (APCs) in T cell differentiation?
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What primarily affects the flexibility of mature T cells in responding to various pathogens?
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Study Notes
CD4 T Cell Commitment
- CD4 T cells can differentiate into various effector lineages: Th1, Th2, and Th17.
- These lineages are determined by the cytokine environment in the lymph node during initial antigen presentation.
Signaling Through Cytokine Receptors
- The JAK:STAT pathway is involved in signaling through cytokine receptors.
CD4 T Cell Fate Determined in Lymph Node
- Effector cells return to the site of infection after initial commitment in the lymph nodes.
- Antigen-presenting cells (APCs) influence CD4 T cell lineage commitment based on the specific pathogen.
- This allows for flexibility in the immune response, enabling the host to combat different pathogens effectively.
Cytokine Milieu Determines CD4 T Cell Fate
- The cytokine milieu dictates whether a CD4 T cell develops into a Th1, Th2, or Th17 lineage.
Polarizing Immunity Toward a Specific Pathogen
- The Th1:Th2 paradigm illustrates how cytokines produced during one response can inhibit the development of the other.
- Th1 responses are associated with intracellular pathogens like viruses and bacteria.
- Th2 responses are associated with extracellular pathogens.
Classical and Alternative Macrophage Activation
- Macrophages exhibit different activation states based on the cytokine environment.
Destruction of an Intracellular Pathogen
- APCs infected with intracellular bacteria induce Th1 immunity.
- The infected APC presents bacterial peptides on MHC-II and produces IL-12, triggering Th1 differentiation.
- Th1 cells express CD40 ligand and produce IFN-γ, which instruct the APC to kill the intracellular bacteria.
Granuloma Formation
- Mycobacteria, such as those causing tuberculosis, can survive within macrophages and resist Th1-mediated killing.
- This leads to the formation of granulomas, characterized by multinucleated giant cells (fused macrophages) and surrounding T cells.
Multiple Effects of Activated Th1 Cells on The Host
- Th1 cells have multiple effects on the host immune system.
- They promote macrophage activation and intracellular pathogen killing.
- They can also trigger production of antibodies.
Production of Antibodies
- Th2 cells produce cytokines (IL-4, IL-5, IL-6) involved in antibody isotype switching.
- IFN-γ (a Th1 cytokine) can stimulate isotype switching towards IgG1 antibodies, enhancing opsonophagocytosis and complement fixation.
Hapten:Carrier Systems and Conjugate Vaccines
- Polysaccharides cannot be presented to T cells, making T cell-independent immunity crucial.
- Conjugate vaccines combine polysaccharides with a protein (like tetanus toxoid) to enhance immunity.
- The protein portion acts as a T-cell epitope, leading to T cell activation and antibody production directed towards the polysaccharide.
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Description
This quiz explores the mechanisms behind CD4 T cell differentiation into various effector lineages such as Th1, Th2, and Th17. It highlights the role of cytokine environments and the JAK:STAT signaling pathway in determining T cell fate and inducing a versatile immune response against pathogens.
