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14 Cards in this Set
- Front
- Back
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What are the mechanisms by which naive T cells migrate into lymphoid organs?
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homing: interaction between L-selectin and ligands expressed by HEV’s
crossing the epithelial barrier: need adhesion molecules and chemokine signals |
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What are the three types of antigen presenting cells?
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-Dendritic cells
-Macrophages -B Cells |
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How do naive T cells interact with antigen presenting cells?
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They adhere through LFA and ICAM
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What are the requirements for naive T-cell activation?
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Keyword: co-stimulation
1) Antigen-specific recognition via MHC-peptide 2) B7/CD28 interaction- danger signal increases B7 expression |
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How are T-cells activated to proliferate?
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IL-2 binds with its receptor on activated T cells, and induces JAK/STAT that causes T cells to enter cell cycle
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How are T-cells able to enter infected tissue
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Effector T cells lose expresison of L-selectin and increase VLA-4 expression to bind with VCAM-1 on infected tissue
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Describe differentiation of activated CD4 T Cells
-what cytokine activates it, what cytokines it releases, what type of immunity |
They can become TH1 cells (via IL-12) and go on to release IL-2, IFN-y, TNF-a, and carry out cell-mediated immunity
They can become TH2 cells (via IL-4) and go onto release IL-4, IL-5, IL-13 and carry out humoral immunity |
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What are the three types of armed effector T cells?
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-Cytotoxic T cells recognize cytoplasmic pathogens (viruses and some bacteria) and tumor antigens
-TH1 cells focus their function on bacteria that grow in intracellular vesicles (cell-mediated) -TH2 cells are important for immune responses against extracellular toxins, pathogens, worms (humoral) |
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Describe the perforin/granzyme pathway involved in CD8 mediated death
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Perforin polymerizes and forms pore through which granzymes can be delivered. Target cells undergo osmotic swelling. Granzymes activate apoptosis in target cell
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Describe the FasL pathway in CD8 mediated death
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activation of FasL on T cell interacts with Fas on target cell, transduces signal to target cell to undergo apoptosis
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How do TH1 cells activate macrophages to become highly bactericidal?
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TH1 produces cytokines that activate macrophages which then kill intracellullar pathogens using lysosomal proteases, oxygen radicals, and nitric oxide. Cytokines released can also influence class switch recombination
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Describe co-stimulation of B-cells by CD4 T cells and the defect that can occur in this pathway
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-Antigen-specific recognition by T cells
-interaction between CD40 (on B cells) and CD40L (on T cells) allows B cells to go on and proliferate and differentiate -hyperimmunoglobulin M syndrome is a lack of CD40 expression |
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Describe the decline phase briefly
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T cells can also induce the expression of inhibitory receptors. For example, receptors that interact with B& to downregulate T cell responses. FasL-Fas mediated cell death on own surface
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Describe memory T-cells briefly
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Do not require costimulatory signals for their activation. Differentiation can occur prior to or after differentiation into specialized effector T cells
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