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27 Cards in this Set

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What are the essential components of antigen recognition
1. T cell receptor complex
2. Antigenic peptide (on APC)
3. MHC proteins (on APC)
How are MHC Class II antigens presented on the cell surface?
EXTRACELLULAR antigen is phagocytized and combinede with an MHC Class II molecule (made from the golgi), then the antigen peptide is presented by the MHC Class II on the cell surface. These cells are on the lymph nodes or spleen and want to present antigen to activate the immune response. The T cell that will recognize this is the CD4+ helper/regulator T cells.
How are MHC Class I antigens presented on the cell surface?
INTRACELLULAR antigen is chopped into peptides, which go to the ER where it combines with the MHC Class I, which then presents the peptide at the cell surface. This is a natural process that happens all the time that happens with self-proteins displaying self-peptide (no problem). But if the cell is infected with a virus, there will be non-self proteins made in the cell that can be chopped into peptides and displayed onto MHC Class I as well. It'll be ATE up by CD8+ T cells
Name three antigen-presenting cells, and which is the most important for activating naive Tcells?
1. Dendritic Cells
2. B-Lymphocytes
3. Macophages

*dendritic cells are most important for activating naive Tcells. Take up antigen, then they move to lymph nodes where they can present the peptides to the T-cells.
**all take antigens, break them up into peptides, and present them on the surface of the cell
Why are dendritic cells the best for antigen presentation to T cells?
Morphology- a lot of processes to take up antigen
Mechanisms- many for taking them up
-capture Ag and migrate to find T cells
-Increase expression of class I and II MHC, CAM, and B7 (secondary signal) while in the lymph node trying to activate the T cells.
What is CD28?
Major molecular signals located on T-cells. When in contact with the APC, the CD28 molecule must contact its ligand, which is B7 (aka CD80/CD86) on the APC. This sends additional signals that lets the T-cell become fully activated
What is CTLA-4?
Helps to turn OFF the T-cell. Once the T-cell is activated and does its thing, it will start to express more CTLA-4 molecule, which also binds to B7 molecules on the APC (binds to same thing as CD28), and when that interaction takes place, it sends a negative signal to become quiet again.
What are T-cell dependent antigens derived from?
Proteins and microproteins. Those things that can be chopped up into peptides and displayed for T-cells to recognize, and T-cells can be activated to help the B-cells.
What are you more likely to have if there are T-cells helping B-cells?
Isotype switching. Provide signals in the form of cytokines that help B-cells switch to different isotypes and production of memory cells.
What is an example of a T-cell independent antigen (TI)?
polysaccharide coating on the surface of some bacteria. can stimulate B-cells without too much T-cell help. Not as good isotype switching, so you get mostly IgM Ab form, and the memory cell generation isnt as strong as well. Not as good of a response, but it's there.
What are the essential components of antigen recognition
1. T cell receptor complex
2. Antigenic peptide (on APC)
3. MHC proteins (on APC)
How are MHC Class II antigens presented on the cell surface?
EXTRACELLULAR antigen is phagocytized and combinede with an MHC Class II molecule (made from the golgi), then the antigen peptide is presented by the MHC Class II on the cell surface. These cells are on the lymph nodes or spleen and want to present antigen to activate the immune response. The T cell that will recognize this is the CD4+ helper/regulator T cells.
How are MHC Class I antigens presented on the cell surface?
INTRACELLULAR antigen is chopped into peptides, which go to the ER where it combines with the MHC Class I, which then presents the peptide at the cell surface. This is a natural process that happens all the time that happens with self-proteins displaying self-peptide (no problem). But if the cell is infected with a virus, there will be non-self proteins made in the cell that can be chopped into peptides and displayed onto MHC Class I as well. It'll be ATE up by CD8+ T cells
Name three antigen-presenting cells, and which is the most important for activating naive Tcells?
1. Dendritic Cells
2. B-Lymphocytes
3. Macophages

*dendritic cells are most important for activating naive Tcells. Take up antigen, then they move to lymph nodes where they can present the peptides to the T-cells.
**all take antigens, break them up into peptides, and present them on the surface of the cell
Why are dendritic cells the best for antigen presentation to T cells?
Morphology- a lot of processes to take up antigen
Mechanisms- many for taking them up
-capture Ag and migrate to find T cells
-Increase expression of class I and II MHC, CAM, and B7 (secondary signal) while in the lymph node trying to activate the T cells.
What is CD28?
Major molecular signals located on T-cells. When in contact with the APC, the CD28 molecule must contact its ligand, which is B7 (aka CD80/CD86). This sends additional signals that lets the T-cell become fully activated
What is CTLA-4?
Helps to turn OFF the T-cell. Once the T-cell is activated and does its thing, it will start to express more CTLA-4 molecule, which also binds to B7 molecules (binds to same thing as CD28), and when that interaction takes place, it sends a negative signal to become quiet again.
What are T-cell dependent antigens derived from?
Proteins and microproteins. Those things that can be chopped up into peptides and displayed for T-cells to recognize, and T-cells can be activated to help the B-cells.
What are you more likely to have if there are T-cells helping B-cells?
Isotype switching. Provide signals in the form of cytokines that help B-cells switch to different isotypes and production of memory cells.
What is an example of a T-cell independent antigen (TI)?
polysaccharide coating on the surface of some bacteria. can stimulate B-cells without too much T-cell help. Not as good isotype switching, so you get mostly IgM Ab form, and the memory cell generation isnt as strong as well. Not as good of a response, but it's there.
What are Ig-alpha and Ig-beta of B-cells similar in function as?
They have the same role as CD3 on T-cells. Ig-alpha, beta, and CD3 are the cytoplasmic components that are attached to the surface molecules. Involved in the intracellular signalling that's phosphorylated to the nucleus.
What is CD40?
Displayed on the B-cell surface. Allows binding with the T-cell with its CD-40 ligand (aka CD154). They need to come in contact in order for the B-cell to undergo ISOTYPE SWITCHING!
What immunodeficiency is related to a lack of CD-40 ligand?
Patients with defect in CD-40 ligand on T-cells will have Immunodeficiency with Hyper-IgM. A lot of IgM but not a lot of other isotypes. Example of T-cell involved in B-cell function.
Th2 T-cell release of IL-4 and IL-13 influences the production of what antibody?
IgE. For allergic responses.
TGF-beta is a suppressive cytokine, but is also involved in isotype switching into...
IgA.
IFN-gamma tends to influence the production of this immunoglobulin..
IgG

(Gamma-->IgG)
What is a superantigen?
Ability to turn on a LOT of T-cells. Superantigens binds to variable regions of T-cell receptors and Class II MHC molecules that activates a much larger percentage of T-cells. This leads to a lot more cytokine production, which can cause problems