Cell Mediated Immunity Flashcards
Describe an immature dendritic cell
Main function is to CAPTURE antigen; high levels of receptors, low levels of MHC and co-stimulatory molecules.
Describe a mature dendritic cell.
Main function is to PRESENT antigen; Opposite receptor and molecule expression than immature dendritic cell.
What does a newly activated T cell secrete?
IL-2 and express high affinity IL-2 receptor. The low affinity receptor is expressed on naive T cells.
Describe the composition of the Low affinity receptor.
Dimer of beta and gamma chain
Describe the composition of the high affinity receptor.
Trimer of beta, gamma and alpha chain; Always expressed on regulatory T cells.
What are the fates of cells in clonal expansion?
They will either become effector cells or memory cells.
What is the role of chemokines and chemokine receptors?
Changes in chemokine receptors and adhesion molecules allow newly activated T cells to exit lymph nodes or spleen, enter the blood circulation and move to the site of inflammation.
How does a dendritic cell control T cell differentiation?
The immunological synapse between a professional APC and Th0 cell. The cytokines released determine the type of T cell.
What determines which cytokines are produced by a dendritic cell or other APC while interacting with a Th0?
- Host genetics
- Type of infection
- Type of TLR engaged on the APC
Understand the type of signal chart and picture
Pg 76
Which cytokine makes a Th0 differentiate into a Th1 cell?
IL-12; Happens during an intracellular infection. IL-18 promotes a Th1 response by amplifying the effects of IL-12. Both IL-12 and 18 help activate NK cells.
Which cytokine makes a Th0 differentiate into a Th2 cell?
IL-4; Happens during an extracellular infection. Mast cells and basophils make IL-4.
Which cytokine makes a Th0 differentiate into a Th17 cell?
IL-23; TGF-B and IL-6 in their differentiation. Response to extracellular bacteria and fungi. Made by dendritic cells and macrophages.
Which cytokine makes a Th0 differentiate into a Treg?
IL-10/TGF-F; Must be in the absence of IL-6.
Which cytokine does Th1 cells secrete?
They secrete IFN-y and IL-2 which stimulates clonal expansion.
What are the effects of IFN-y secretion?
- Activates macrophages
- Upregulates MHC 1 and 2 on APCs and endothelium.
- Inhibits development of Th2 and Th17.
- Activates isotype switching in B cells to make IgG
Describe the positive feedback cycle between macrophages and Th1 cells.
IFN-y activated macrophages make IL-12, which promotes Th1 cell development. Th1 cells then secrete IFN-y; Delay type hypersensitivity.
What does Th2 cells secrete?
IL-4, 21,5,6,10 and 13.
What does IL-4 do?
- Induce Th0 into Th2
- Suppresses inflammatory function of macrophages
- In conjunction with with IL-21,5 and 6, it promotes proliferation of B cells and isotype switching to IgG and IgM
- In conjunction with IL-13 it promotes isotype switching to IgE and wound healing by alternative macrophages.
What does IL-13 do?
Stimulates mast cell proliferation
What does IL-10 do?
Surpresses Th1 response.
Which cells make IL-17?
Th17 cells;
- Stimulates changes in vessels that increase chemotaxis of neutrophils, especially in skin and mucosa.
- Defense against extracellular bacteria and parasites.
- Inhibited by Th1 or Th2 response
Know chart on pg 84
see coursepack
How do CD8s stop an intracellular pathogen?
Does not require co-stimulation through CD28/B7 interaction; Induces apoptosis.
- Cytotoxic granules containing perforin and granzymes.
- Fas ligand on CD8 binds to Fas receptor on target cell.
- CD8s secrete IFN-y which activates macrophages to phagocytose infected cells.
What are the two mechanisms of controlling T cell responses?
- Lack of stimulatory signals
- Inhibitory receptors
- Death receptors
