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17 Cards in this Set
- Front
- Back
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What are the 2 categories of cell-mediated responses?
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Phagocyte activation & cell-mediated cytotoxicity
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What is the role of macrophages in immunity?
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Can engulf & kill some pathogens. Other pathogens are resistent so macros need to be activated before they can kill such pathogens
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Describe T-cell activation.
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Engulf-> process-> present to CD4 Th1 (MHCII)-> T-cell express IL-2R & secrete IL2-> clonal expansion->Effector & Memory Th1 cells
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Describe the effector phase (macro activation).
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Upon another Ag exposure effector Th1 binds MHCII-> IFN-gamma secreted & express CD40L-> IFN binds macro & expresses CD40-> LPS or TNF (w/ IFN) activates macro
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Fcn of IL2
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Prolif & activation of T-cells. Enhances synthesis of other cytokines (TNF, IFN, & LT)
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Fcn of IFN-gamma
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Activates macros. Induces hydrolytic enzymes, inc MHCI & II expression, enhance Ag presentation. Mediates anti-viral activity
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Fcn of GM-CSF
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Activates macros.
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Fcn of TNF-alpha
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Acts synergistically w/ IFN to activate macros. W/ TL they augment endothelial cell expression of adhesion molec & activates neutrophils (inc phago activity)
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Fcn of MIF
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Prevents inflamm cells from leaving the site; enhance expression of adhesion molec
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What are the cytokines produced by macros?
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IL1 (fever & induces more cytokines), IL6 (release acute phase protein), TNF (inc expression of ELAM1, ICAM, VCAM; adhesion), chemokines (attract other macros), reactive oxy species (anti-microbial), NO (vasodilate), enzymes (antimicrobial)
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What confers Ag specificity in CMI?
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Helper T-cells. Macro activation is Ag specific but via Th1 cells but once activated killing is nonspecific
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What can inhibit macro activation?
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Th2 cytokines (IL4, IL10, IL13, TGF-beta
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Fcn of cytotoxic T-lymphocytes?
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Kill tumor & viral cells. Also transplant rejection
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How are CTL activated?
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Virus infected dendritic cells express B7 & activate CD8 CTL->IL2 production-> prolif. OR APC stim effector CD4 Th which in turn activates APC-> APC expresses B7 & stim CD8CTL. OR APC activates CD4 Th to make IL2 & CD8 CTL to express IL2 R-> activation
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What are the 3 steps involved in cytolysis?
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CTL binding to target cells, degranulation of perforin & granzyme granules-> release into space, & apoptosis. Perforin creates pore & granzymes enter-> either kill directly or initate apoptosis (caspases & endonucleases)
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What are the other apoptotic inducers?
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TNF-alpha & Fas ligand (nonspecific)
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Fcn of NK cells
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Activated by IFN-alpha/beta & TNF-alpha-> Kill tumor & virus-infected cells via perforins/granzymes, TNF, FasL. Downreg by IL-10, express inhibitory (prevent killing healthy cells & activating factors (kill cells that lost MHCI)
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