Term
| What are general characteristics of gamma-delta T-cells? |
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Definition
| There is no memory as they are not MHC-restricted. They are found in mucosal epithelium, rarely in blood |
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Term
| What do gamma-9-delta-2 T-cells recognize? |
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Definition
| Phosphorylated metabolism intermediates and M. tuberculosis |
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Term
| What are gamma-delta-1-T-cells? |
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Definition
| Intra-epithelial lypmhocytes that recognize MICA and MICB. These receptors are upregulated by infected cells, turning them into APCs |
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Term
| What do NKT cells recognized? |
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Definition
| They have ab TCRs but instead of recognizing antigens on MHC they recognize lipids on CD1D |
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Term
| What do NK cells respond to? |
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Definition
| They don't have TCRs or CD3; they are an early response to intracellular infections, responding to MICA/B |
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Term
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Definition
| They come from common lymphoid progenitor (CLP) cells in the bone marrow |
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Term
| What are the physical characteristics of NK cells? |
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Definition
| Larger than T-cells with more granules. Armed for immediated release of cytolytic granules. No memory. Not sensitive to antigens. Highly expressed CD56 in tissues. |
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Term
| What effect do infected cells have on NK cells? |
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Definition
| They produce IFN-a and IFN-b, which induce further NK activation and proliferation |
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Term
| What do effector NK cells do? |
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Definition
| They produce IFN-y, which inhibits viral replication, and TNF-a, inducing macrophages to release IL-12 (activates NK cells) and IL-15 (necessary for survival) |
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Term
| What is release by effector NK cells? |
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Definition
| Cytotoxic perforin, granzymes, and FasL, like CTL-cells |
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Term
| What links the adaptive and innate immune systems? |
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Definition
| Macrophages and dendritic cells |
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Term
| Why can the innate immune system not adapt? |
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Definition
| There is no V(D)J recombination or Rag genes |
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Term
| What are the receptors on NK cells? |
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Definition
| Two functional groups: activating and inhibiting |
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Term
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Definition
| They are found on inhibitory receptors and have phosphatase activity and cease signaling |
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Term
| What provides activating signals? |
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Definition
| Immunoreceptor tyrosine-based activating motifs |
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Term
| What are the forms the receptors can take? |
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Definition
| Immunoglobulin-like proteins or lectin-like carbohydrates |
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Term
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Definition
| An activating lectin-like receptor for MIC ligands found on every NK-cell |
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Term
| What are MIC ligands similar to? |
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Definition
| They are structurally similar to HLA class I, but do not involve B2-ug |
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Term
| What mediates NK cell activation? |
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Definition
| The summation of activating and inhibitory signals mediates activation similar to neurons |
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Term
| What are common inhibitory signals? |
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Definition
| Usually binding to HLA class I. HLA-E acts as a ligand and presents elader sequences from HLA-A, B, and C from healthy cells to the CD94:NKG2A receptor. HLA class I binding to Killer-cell Ig-like receptors (KIRs). |
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Term
| What happens to cells without HLA class I? |
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Definition
| Some pathogens can down-regulate HLA class-I. CTL cells can't respond but NK cells can. |
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Term
| Does a lack of inhibition stimulate NK cells? |
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Definition
| No, they must be activated too |
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Term
| How do NK cells signal antibody-dependent cell-mediated cytotoxicity? |
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Definition
| They can bind to Fc regions on IgG1 and IgG3 causing receptor-cross-linking |
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Term
| What are the Fc regions on IgG1 and IgG3? |
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Definition
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Term
| What is the closest NK cells can get to memory? |
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Definition
| FcyRIII receptors are complexed to ITAMs. The ADCC (antibody-dependent cell-mediated cytotoxicity) signal results in apoptosis of the target cell as a secondary immune response. |
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Term
| What require important responses by NK cells? |
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Definition
| Viruses, intracellular bacteria, tumor cells, and rejection of transplanted allogeneic hematopoietic grafts |
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Term
| What is the "missing-self" hypothesis? |
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Definition
| NK cells do not attack healthy autologous cells because NK cells express inhibitory receptors (ITIM) which recognize "self" MHC (HLA) class I molecules |
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Term
| What is Antibody-dependent cell-mediated cytotoxicity (ADCC)? |
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Definition
| Antibody binds antigens on surface of target cell. Fc receptors on NK cell recognize bound Ab. Cross-linking of Fc receptors signals the NK cell to kill the target cell, which dies by apoptosis |
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