Term
| Name two ways antigen activates T cells. |
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Definition
1. Draining in lymph
2. Capture, processing, and presentation by dendritic cells (main) and macrophages (lesser extent) |
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Term
| Describe 2 ways dendritic cells obtain and process pathogens. |
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Definition
1. Receptors (mannose, Toll-like receptors, receptor mediated endocytosis)-->processed-->MHC II
2. Macropinocytosis (nonspecific ingestion of large amounts of extracellular fluid) |
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Term
| Name 2 effects of activation of a dendritic cell. |
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Definition
1. Increase efficiency with which antigens are taken up and processed for presentation by MHC II.
2. Expression of CCR7 (receptor for chemokine CCL21)-->enter draining lymph node and concentrate on presentation to naive T cells. |
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Term
| Name chemokine and adhesion molecules that attract Naive T cells to a node. |
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Definition
CCL19, CCL21 (secreted in cortex, bind to HEV to make concentration gradient)
Addressins CD34, Glycam-1 (on surface of HEV, bound by L-selectin on T cell surface) |
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Term
| What are 2 ways that naive T cells enter a lymph node? |
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Definition
1. Blood capillaries (bind to HEV)
2. Lymph (enter upstream and get carried down, don't have to cross HEV) |
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Term
| Which cells deliver a co-stimulatory signal to activate naive T-cells? |
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Definition
Professional antigen-presenting cells:
1. Dendritic Cells
2. B cells
3. Macrophages |
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Term
| What is the cell surface protein on naive T cells that receives the co-stimulatory signal, and what are its ligands? |
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Definition
| CD28; ligands are CD80/CD86 (occurs after TCR signaling) |
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Term
| True or False: In the absence of infection, antigen presenting cells do not express co-stimulatory molecules. |
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Definition
| True: induced by signaling from T cell receptors, inflammatory cytokines |
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Term
| True or False: Vaccinations contain microbe fragments. |
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Definition
| True: they are needed to fully stimulate the immune system. |
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Term
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Definition
| Immunoreceptor Tyrosine-based Activation Motifs (cytoplasmic tail of CD3 proteins) |
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Term
| What is the 3rd required signal for T cell activation? What does it control? |
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Definition
| IL-2 (autocrine); drives clonal expansion of activated cell |
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Term
| True or False: IL-2 receptors are expressed in high density on T cells. |
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Definition
| False: low-affinity form initially, but shifts to high affinity form with activation and new gene expression. |
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Term
| After an antigen binds to a T cell receptor, what happens to the ITAMS in CD3? |
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Definition
| They are phosphorylated by protein tyrosine kinases. Enzymes and signaling molecules bind to these phosphorylated residues and result in altered gene expression. |
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Term
| What is the role of CD4 or CD8 in T cell signaling? What protein tyrosine kinase are they associated with? |
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Definition
| They are associated with Lck, it activates a protein tyrosine kinase called ZAP-70, which binds to the zeta chain of the TCR complex. |
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Term
| What 3 signaling pathways does ZAP-70 trigger? |
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Definition
1. Calcium influx, inositol triphosphate activates NFAT (Nuclear Factor of Activated T cell, a transcriptional activator)
2. Induces transcription factor NFkB
3. Activates Ras-->activates AP-1 (transcription factor) |
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Term
| True or False: Transplant rejection blocking drugs inhibit IL-2 production. |
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Definition
| True: they suppress activation and differentiation of naive T cells and all immune responses that require activated T cells. |
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Term
| Describe TH1 cells (what do they secrete, what does it lead to). |
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Definition
Secrete IL-2 and interferon gamma
Leads to macrophage activation, inflammation, and production of opsonizing antibodies |
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Term
| Describe the TH2 cell (what do they secrete, what does it lead to). |
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Definition
Secrete IL-4 and IL-5
Leads to B cell differentiation and production of neutralizing antibodies. |
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Term
| Describe Treg cells (what do they secrete, what does it lead to). |
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Definition
Secrete TGF-beta, IL-10
Limits self reaction, promotes wound healing. |
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Term
| What are the biases for TH1 or TH2 responses? (cell-mediated immunity or humoral immunity) |
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Definition
TH1: cell-mediated immunity
TH2: humoral immunity |
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Term
| How do CD4 T cells help activate naive CD8 T cells? |
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Definition
| Effector CD4 T cells secrete cytokines that induce antigen presenting cells to increase their level of co-stimulatory molecules. |
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Term
| What is contained in the lytic granules released by CD8 cytotoxic T cells? (2 things) |
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Definition
1. performin (forms channels)
2. granzymes (cleave cytoplasmic proteins to induce DNA damage and apoptosis) |
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Term
| What is the role of the Fas ligand or LT on activated TH1 cells? |
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Definition
| Kills chronically infected macrophages, releasing bacteria to be destroyed by healthy ones. |
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Term
| What is the role of INF gamma and CD40 ligand on activated TH1 cells? |
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Definition
| Activates macrophages to destroy engulfed bacteria. |
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Term
| What is the role of IL-2 on activated TH1 cells? |
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Definition
| Induces T cell proliferation. |
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Term
| What is the role of IL-3 and GM-CSF in activated TH1 cells? |
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Definition
| Induces macrophage differentiation in bone marrow. |
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Term
| What is the role of TNF-alpha and LT in activated TH1 cells? |
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Definition
| Activates endothelium to induce macrophage adhesion and exit from blood vessels at site of infection. |
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Term
| What is the role of CXCL2 in activated TH1 cells? |
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Definition
| Cause macrophages to accumulate at site of infection. |
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Term
| How do TH2 cells help B cells mount an antibody response? |
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Definition
| Using interactions between CD40 ligand and CD40 receptors and secretion of IL-4, IL-5, and IL-6, drives cell division and further differentiation to plasma cells. |
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Term
| How do Treg cells suppress an autoimmune response? |
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Definition
| Immunosuppressive cytokines IL-4, IL-10 and TGF-beta. |
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Term
| What cytokine do Treg cells secrete to promote self tolerance? |
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Definition
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